linux/fs/notify/fsnotify.c

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// SPDX-License-Identifier: GPL-2.0-or-later
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*/
#include <linux/dcache.h>
#include <linux/fs.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 08:04:11 +00:00
#include <linux/gfp.h>
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mount.h>
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
#include <linux/srcu.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
/*
* Clear all of the marks on an inode when it is being evicted from core
*/
void __fsnotify_inode_delete(struct inode *inode)
{
fsnotify_clear_marks_by_inode(inode);
}
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{
fsnotify_clear_marks_by_mount(mnt);
}
/**
* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
* @sb: superblock being unmounted.
*
* Called during unmount with no locks held, so needs to be safe against
* concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
*/
static void fsnotify_unmount_inodes(struct super_block *sb)
{
struct inode *inode, *iput_inode = NULL;
spin_lock(&sb->s_inode_list_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
/*
* We cannot __iget() an inode in state I_FREEING,
* I_WILL_FREE, or I_NEW which is fine because by that point
* the inode cannot have any associated watches.
*/
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
spin_unlock(&inode->i_lock);
continue;
}
/*
* If i_count is zero, the inode cannot have any watches and
Rename superblock flags (MS_xyz -> SB_xyz) This is a pure automated search-and-replace of the internal kernel superblock flags. The s_flags are now called SB_*, with the names and the values for the moment mirroring the MS_* flags that they're equivalent to. Note how the MS_xyz flags are the ones passed to the mount system call, while the SB_xyz flags are what we then use in sb->s_flags. The script to do this was: # places to look in; re security/*: it generally should *not* be # touched (that stuff parses mount(2) arguments directly), but # there are two places where we really deal with superblock flags. FILES="drivers/mtd drivers/staging/lustre fs ipc mm \ include/linux/fs.h include/uapi/linux/bfs_fs.h \ security/apparmor/apparmorfs.c security/apparmor/include/lib.h" # the list of MS_... constants SYMS="RDONLY NOSUID NODEV NOEXEC SYNCHRONOUS REMOUNT MANDLOCK \ DIRSYNC NOATIME NODIRATIME BIND MOVE REC VERBOSE SILENT \ POSIXACL UNBINDABLE PRIVATE SLAVE SHARED RELATIME KERNMOUNT \ I_VERSION STRICTATIME LAZYTIME SUBMOUNT NOREMOTELOCK NOSEC BORN \ ACTIVE NOUSER" SED_PROG= for i in $SYMS; do SED_PROG="$SED_PROG -e s/MS_$i/SB_$i/g"; done # we want files that contain at least one of MS_..., # with fs/namespace.c and fs/pnode.c excluded. L=$(for i in $SYMS; do git grep -w -l MS_$i $FILES; done| sort|uniq|grep -v '^fs/namespace.c'|grep -v '^fs/pnode.c') for f in $L; do sed -i $f $SED_PROG; done Requested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-27 21:05:09 +00:00
* doing an __iget/iput with SB_ACTIVE clear would actually
* evict all inodes with zero i_count from icache which is
* unnecessarily violent and may in fact be illegal to do.
* However, we should have been called /after/ evict_inodes
* removed all zero refcount inodes, in any case. Test to
* be sure.
*/
if (!atomic_read(&inode->i_count)) {
spin_unlock(&inode->i_lock);
continue;
}
__iget(inode);
spin_unlock(&inode->i_lock);
spin_unlock(&sb->s_inode_list_lock);
iput(iput_inode);
/* for each watch, send FS_UNMOUNT and then remove it */
fsnotify_inode(inode, FS_UNMOUNT);
fsnotify_inode_delete(inode);
iput_inode = inode;
cond_resched();
spin_lock(&sb->s_inode_list_lock);
}
spin_unlock(&sb->s_inode_list_lock);
iput(iput_inode);
}
void fsnotify_sb_delete(struct super_block *sb)
{
fsnotify_unmount_inodes(sb);
fsnotify_clear_marks_by_sb(sb);
/* Wait for outstanding object references from connectors */
wait_var_event(&sb->s_fsnotify_connectors,
!atomic_long_read(&sb->s_fsnotify_connectors));
}
/*
* Given an inode, first check if we care what happens to our children. Inotify
* and dnotify both tell their parents about events. If we care about any event
* on a child we run all of our children and set a dentry flag saying that the
* parent cares. Thus when an event happens on a child it can quickly tell if
* if there is a need to find a parent and send the event to the parent.
*/
void __fsnotify_update_child_dentry_flags(struct inode *inode)
{
struct dentry *alias;
int watched;
if (!S_ISDIR(inode->i_mode))
return;
/* determine if the children should tell inode about their events */
watched = fsnotify_inode_watches_children(inode);
spin_lock(&inode->i_lock);
/* run all of the dentries associated with this inode. Since this is a
* directory, there damn well better only be one item on this list */
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
struct dentry *child;
/* run all of the children of the original inode and fix their
* d_flags to indicate parental interest (their parent is the
* original inode) */
spin_lock(&alias->d_lock);
list_for_each_entry(child, &alias->d_subdirs, d_child) {
if (!child->d_inode)
continue;
spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
if (watched)
child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
else
child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
spin_unlock(&child->d_lock);
}
spin_unlock(&alias->d_lock);
}
spin_unlock(&inode->i_lock);
}
/* Are inode/sb/mount interested in parent and name info with this event? */
static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
__u32 mask)
{
__u32 marks_mask = 0;
/* We only send parent/name to inode/sb/mount for events on non-dir */
if (mask & FS_ISDIR)
return false;
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
/*
* All events that are possible on child can also may be reported with
* parent/name info to inode/sb/mount. Otherwise, a watching parent
* could result in events reported with unexpected name info to sb/mount.
*/
BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);
/* Did either inode/sb/mount subscribe for events with parent/name? */
marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
if (mnt)
marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);
/* Did they subscribe for this event with parent/name info? */
return mask & marks_mask;
}
/*
* Notify this dentry's parent about a child's events with child name info
* if parent is watching or if inode/sb/mount are interested in events with
* parent and name info.
*
* Notify only the child without name info if parent is not watching and
* inode/sb/mount are not interested in events with parent and name info.
*/
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
int data_type)
{
const struct path *path = fsnotify_data_path(data, data_type);
struct mount *mnt = path ? real_mount(path->mnt) : NULL;
struct inode *inode = d_inode(dentry);
struct dentry *parent;
bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
fanotify: fix logic of reporting name info with watched parent The victim inode's parent and name info is required when an event needs to be delivered to a group interested in filename info OR when the inode's parent is interested in an event on its children. Let us call the first condition 'parent_needed' and the second condition 'parent_interested'. In fsnotify_parent(), the condition where the inode's parent is interested in some events on its children, but not necessarily interested the specific event is called 'parent_watched'. fsnotify_parent() tests the condition (!parent_watched && !parent_needed) for sending the event without parent and name info, which is correct. It then wrongly assumes that parent_watched implies !parent_needed and tests the condition (parent_watched && !parent_interested) for sending the event without parent and name info, which is wrong, because parent may still be needed by some group. For example, after initializing a group with FAN_REPORT_DFID_NAME and adding a FAN_MARK_MOUNT with FAN_OPEN mask, open events on non-directory children of "testdir" are delivered with file name info. After adding another mark to the same group on the parent "testdir" with FAN_CLOSE|FAN_EVENT_ON_CHILD mask, open events on non-directory children of "testdir" are no longer delivered with file name info. Fix the logic and use auxiliary variables to clarify the conditions. Fixes: 9b93f33105f5 ("fsnotify: send event with parent/name info to sb/mount/non-dir marks") Cc: stable@vger.kernel.org#v5.9 Link: https://lore.kernel.org/r/20201108105906.8493-1-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-11-08 10:59:06 +00:00
bool parent_needed, parent_interested;
__u32 p_mask;
struct inode *p_inode = NULL;
struct name_snapshot name;
struct qstr *file_name = NULL;
int ret = 0;
/*
* Do inode/sb/mount care about parent and name info on non-dir?
* Do they care about any event at all?
*/
if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
(!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
return 0;
parent = NULL;
fanotify: fix logic of reporting name info with watched parent The victim inode's parent and name info is required when an event needs to be delivered to a group interested in filename info OR when the inode's parent is interested in an event on its children. Let us call the first condition 'parent_needed' and the second condition 'parent_interested'. In fsnotify_parent(), the condition where the inode's parent is interested in some events on its children, but not necessarily interested the specific event is called 'parent_watched'. fsnotify_parent() tests the condition (!parent_watched && !parent_needed) for sending the event without parent and name info, which is correct. It then wrongly assumes that parent_watched implies !parent_needed and tests the condition (parent_watched && !parent_interested) for sending the event without parent and name info, which is wrong, because parent may still be needed by some group. For example, after initializing a group with FAN_REPORT_DFID_NAME and adding a FAN_MARK_MOUNT with FAN_OPEN mask, open events on non-directory children of "testdir" are delivered with file name info. After adding another mark to the same group on the parent "testdir" with FAN_CLOSE|FAN_EVENT_ON_CHILD mask, open events on non-directory children of "testdir" are no longer delivered with file name info. Fix the logic and use auxiliary variables to clarify the conditions. Fixes: 9b93f33105f5 ("fsnotify: send event with parent/name info to sb/mount/non-dir marks") Cc: stable@vger.kernel.org#v5.9 Link: https://lore.kernel.org/r/20201108105906.8493-1-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-11-08 10:59:06 +00:00
parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
if (!parent_watched && !parent_needed)
goto notify;
/* Does parent inode care about events on children? */
parent = dget_parent(dentry);
p_inode = parent->d_inode;
p_mask = fsnotify_inode_watches_children(p_inode);
if (unlikely(parent_watched && !p_mask))
__fsnotify_update_child_dentry_flags(p_inode);
/*
* Include parent/name in notification either if some notification
fanotify: fix logic of reporting name info with watched parent The victim inode's parent and name info is required when an event needs to be delivered to a group interested in filename info OR when the inode's parent is interested in an event on its children. Let us call the first condition 'parent_needed' and the second condition 'parent_interested'. In fsnotify_parent(), the condition where the inode's parent is interested in some events on its children, but not necessarily interested the specific event is called 'parent_watched'. fsnotify_parent() tests the condition (!parent_watched && !parent_needed) for sending the event without parent and name info, which is correct. It then wrongly assumes that parent_watched implies !parent_needed and tests the condition (parent_watched && !parent_interested) for sending the event without parent and name info, which is wrong, because parent may still be needed by some group. For example, after initializing a group with FAN_REPORT_DFID_NAME and adding a FAN_MARK_MOUNT with FAN_OPEN mask, open events on non-directory children of "testdir" are delivered with file name info. After adding another mark to the same group on the parent "testdir" with FAN_CLOSE|FAN_EVENT_ON_CHILD mask, open events on non-directory children of "testdir" are no longer delivered with file name info. Fix the logic and use auxiliary variables to clarify the conditions. Fixes: 9b93f33105f5 ("fsnotify: send event with parent/name info to sb/mount/non-dir marks") Cc: stable@vger.kernel.org#v5.9 Link: https://lore.kernel.org/r/20201108105906.8493-1-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-11-08 10:59:06 +00:00
* groups require parent info or the parent is interested in this event.
*/
fanotify: fix logic of reporting name info with watched parent The victim inode's parent and name info is required when an event needs to be delivered to a group interested in filename info OR when the inode's parent is interested in an event on its children. Let us call the first condition 'parent_needed' and the second condition 'parent_interested'. In fsnotify_parent(), the condition where the inode's parent is interested in some events on its children, but not necessarily interested the specific event is called 'parent_watched'. fsnotify_parent() tests the condition (!parent_watched && !parent_needed) for sending the event without parent and name info, which is correct. It then wrongly assumes that parent_watched implies !parent_needed and tests the condition (parent_watched && !parent_interested) for sending the event without parent and name info, which is wrong, because parent may still be needed by some group. For example, after initializing a group with FAN_REPORT_DFID_NAME and adding a FAN_MARK_MOUNT with FAN_OPEN mask, open events on non-directory children of "testdir" are delivered with file name info. After adding another mark to the same group on the parent "testdir" with FAN_CLOSE|FAN_EVENT_ON_CHILD mask, open events on non-directory children of "testdir" are no longer delivered with file name info. Fix the logic and use auxiliary variables to clarify the conditions. Fixes: 9b93f33105f5 ("fsnotify: send event with parent/name info to sb/mount/non-dir marks") Cc: stable@vger.kernel.org#v5.9 Link: https://lore.kernel.org/r/20201108105906.8493-1-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-11-08 10:59:06 +00:00
parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
if (parent_needed || parent_interested) {
/* When notifying parent, child should be passed as data */
WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));
/* Notify both parent and child with child name info */
take_dentry_name_snapshot(&name, dentry);
file_name = &name.name;
fanotify: fix logic of reporting name info with watched parent The victim inode's parent and name info is required when an event needs to be delivered to a group interested in filename info OR when the inode's parent is interested in an event on its children. Let us call the first condition 'parent_needed' and the second condition 'parent_interested'. In fsnotify_parent(), the condition where the inode's parent is interested in some events on its children, but not necessarily interested the specific event is called 'parent_watched'. fsnotify_parent() tests the condition (!parent_watched && !parent_needed) for sending the event without parent and name info, which is correct. It then wrongly assumes that parent_watched implies !parent_needed and tests the condition (parent_watched && !parent_interested) for sending the event without parent and name info, which is wrong, because parent may still be needed by some group. For example, after initializing a group with FAN_REPORT_DFID_NAME and adding a FAN_MARK_MOUNT with FAN_OPEN mask, open events on non-directory children of "testdir" are delivered with file name info. After adding another mark to the same group on the parent "testdir" with FAN_CLOSE|FAN_EVENT_ON_CHILD mask, open events on non-directory children of "testdir" are no longer delivered with file name info. Fix the logic and use auxiliary variables to clarify the conditions. Fixes: 9b93f33105f5 ("fsnotify: send event with parent/name info to sb/mount/non-dir marks") Cc: stable@vger.kernel.org#v5.9 Link: https://lore.kernel.org/r/20201108105906.8493-1-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-11-08 10:59:06 +00:00
if (parent_interested)
mask |= FS_EVENT_ON_CHILD;
}
notify:
ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);
if (file_name)
release_dentry_name_snapshot(&name);
dput(parent);
return ret;
}
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
EXPORT_SYMBOL_GPL(__fsnotify_parent);
static int fsnotify_handle_inode_event(struct fsnotify_group *group,
struct fsnotify_mark *inode_mark,
u32 mask, const void *data, int data_type,
struct inode *dir, const struct qstr *name,
u32 cookie)
{
const struct path *path = fsnotify_data_path(data, data_type);
struct inode *inode = fsnotify_data_inode(data, data_type);
const struct fsnotify_ops *ops = group->ops;
if (WARN_ON_ONCE(!ops->handle_inode_event))
return 0;
if (WARN_ON_ONCE(!inode && !dir))
return 0;
if ((inode_mark->flags & FSNOTIFY_MARK_FLAG_EXCL_UNLINK) &&
path && d_unlinked(path->dentry))
return 0;
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
/* Check interest of this mark in case event was sent with two marks */
if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
return 0;
return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
}
static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
const void *data, int data_type,
struct inode *dir, const struct qstr *name,
u32 cookie, struct fsnotify_iter_info *iter_info)
{
struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
int ret;
if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
return 0;
/*
* For FS_RENAME, 'dir' is old dir and 'data' is new dentry.
* The only ->handle_inode_event() backend that supports FS_RENAME is
* dnotify, where it means file was renamed within same parent.
*/
if (mask & FS_RENAME) {
struct dentry *moved = fsnotify_data_dentry(data, data_type);
if (dir != moved->d_parent->d_inode)
return 0;
}
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
if (parent_mark) {
ret = fsnotify_handle_inode_event(group, parent_mark, mask,
data, data_type, dir, name, 0);
if (ret)
return ret;
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
}
if (!inode_mark)
return 0;
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
if (mask & FS_EVENT_ON_CHILD) {
/*
* Some events can be sent on both parent dir and child marks
* (e.g. FS_ATTRIB). If both parent dir and child are
* watching, report the event once to parent dir with name (if
* interested) and once to child without name (if interested).
* The child watcher is expecting an event without a file name
* and without the FS_EVENT_ON_CHILD flag.
*/
mask &= ~FS_EVENT_ON_CHILD;
dir = NULL;
name = NULL;
}
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
dir, name, cookie);
}
static int send_to_group(__u32 mask, const void *data, int data_type,
struct inode *dir, const struct qstr *file_name,
u32 cookie, struct fsnotify_iter_info *iter_info)
{
struct fsnotify_group *group = NULL;
__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
__u32 marks_mask = 0;
__u32 marks_ignored_mask = 0;
struct fsnotify_mark *mark;
int type;
if (!iter_info->report_mask)
return 0;
/* clear ignored on inode modification */
if (mask & FS_MODIFY) {
fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
if (!(mark->flags &
FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
mark->ignored_mask = 0;
}
}
/* Are any of the group marks interested in this event? */
fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
group = mark->group;
marks_mask |= mark->mask;
marks_ignored_mask |= mark->ignored_mask;
}
pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
__func__, group, mask, marks_mask, marks_ignored_mask,
data, data_type, dir, cookie);
if (!(test_mask & marks_mask & ~marks_ignored_mask))
return 0;
if (group->ops->handle_event) {
return group->ops->handle_event(group, mask, data, data_type, dir,
file_name, cookie, iter_info);
}
return fsnotify_handle_event(group, mask, data, data_type, dir,
file_name, cookie, iter_info);
}
static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
{
struct fsnotify_mark_connector *conn;
struct hlist_node *node = NULL;
conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
if (conn)
node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
}
static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
{
struct hlist_node *node = NULL;
if (mark)
node = srcu_dereference(mark->obj_list.next,
&fsnotify_mark_srcu);
return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
}
/*
* iter_info is a multi head priority queue of marks.
* Pick a subset of marks from queue heads, all with the same group
* and set the report_mask to a subset of the selected marks.
* Returns false if there are no more groups to iterate.
*/
static bool fsnotify_iter_select_report_types(
struct fsnotify_iter_info *iter_info)
{
struct fsnotify_group *max_prio_group = NULL;
struct fsnotify_mark *mark;
int type;
/* Choose max prio group among groups of all queue heads */
fsnotify_foreach_iter_type(type) {
mark = iter_info->marks[type];
if (mark &&
fsnotify_compare_groups(max_prio_group, mark->group) > 0)
max_prio_group = mark->group;
}
if (!max_prio_group)
return false;
/* Set the report mask for marks from same group as max prio group */
iter_info->current_group = max_prio_group;
iter_info->report_mask = 0;
fsnotify_foreach_iter_type(type) {
mark = iter_info->marks[type];
if (mark && mark->group == iter_info->current_group) {
/*
* FSNOTIFY_ITER_TYPE_PARENT indicates that this inode
* is watching children and interested in this event,
* which is an event possible on child.
* But is *this mark* watching children?
*/
if (type == FSNOTIFY_ITER_TYPE_PARENT &&
!(mark->mask & FS_EVENT_ON_CHILD))
continue;
fsnotify_iter_set_report_type(iter_info, type);
}
}
return true;
}
/*
* Pop from iter_info multi head queue, the marks that belong to the group of
* current iteration step.
*/
static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
{
struct fsnotify_mark *mark;
int type;
/*
* We cannot use fsnotify_foreach_iter_mark_type() here because we
* may need to advance a mark of type X that belongs to current_group
* but was not selected for reporting.
*/
fsnotify_foreach_iter_type(type) {
mark = iter_info->marks[type];
if (mark && mark->group == iter_info->current_group)
iter_info->marks[type] =
fsnotify_next_mark(iter_info->marks[type]);
}
}
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
/*
* fsnotify - This is the main call to fsnotify.
*
* The VFS calls into hook specific functions in linux/fsnotify.h.
* Those functions then in turn call here. Here will call out to all of the
* registered fsnotify_group. Those groups can then use the notification event
* in whatever means they feel necessary.
*
* @mask: event type and flags
* @data: object that event happened on
* @data_type: type of object for fanotify_data_XXX() accessors
* @dir: optional directory associated with event -
* if @file_name is not NULL, this is the directory that
* @file_name is relative to
* @file_name: optional file name associated with event
* @inode: optional inode associated with event -
* If @dir and @inode are both non-NULL, event may be
* reported to both.
* @cookie: inotify rename cookie
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
*/
int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
const struct qstr *file_name, struct inode *inode, u32 cookie)
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
{
const struct path *path = fsnotify_data_path(data, data_type);
struct super_block *sb = fsnotify_data_sb(data, data_type);
struct fsnotify_iter_info iter_info = {};
struct mount *mnt = NULL;
struct inode *inode2 = NULL;
struct dentry *moved;
int inode2_type;
int ret = 0;
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
__u32 test_mask, marks_mask;
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
if (path)
mnt = real_mount(path->mnt);
if (!inode) {
/* Dirent event - report on TYPE_INODE to dir */
inode = dir;
/* For FS_RENAME, inode is old_dir and inode2 is new_dir */
if (mask & FS_RENAME) {
moved = fsnotify_data_dentry(data, data_type);
inode2 = moved->d_parent->d_inode;
inode2_type = FSNOTIFY_ITER_TYPE_INODE2;
}
} else if (mask & FS_EVENT_ON_CHILD) {
/*
fsnotify: fix events reported to watching parent and child fsnotify_parent() used to send two separate events to backends when a parent inode is watching children and the child inode is also watching. In an attempt to avoid duplicate events in fanotify, we unified the two backend callbacks to a single callback and handled the reporting of the two separate events for the relevant backends (inotify and dnotify). However the handling is buggy and can result in inotify and dnotify listeners receiving events of the type they never asked for or spurious events. The problem is the unified event callback with two inode marks (parent and child) is called when any of the parent and child inodes are watched and interested in the event, but the parent inode's mark that is interested in the event on the child is not necessarily the one we are currently reporting to (it could belong to a different group). So before reporting the parent or child event flavor to backend we need to check that the mark is really interested in that event flavor. The semantics of INODE and CHILD marks were hard to follow and made the logic more complicated than it should have been. Replace it with INODE and PARENT marks semantics to hopefully make the logic more clear. Thanks to Hugh Dickins for spotting a bug in the earlier version of this patch. Fixes: 497b0c5a7c06 ("fsnotify: send event to parent and child with single callback") CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202120713.702387-4-amir73il@gmail.com Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-12-02 12:07:09 +00:00
* Event on child - report on TYPE_PARENT to dir if it is
* watching children and on TYPE_INODE to child.
*/
inode2 = dir;
inode2_type = FSNOTIFY_ITER_TYPE_PARENT;
}
/*
* Optimization: srcu_read_lock() has a memory barrier which can
* be expensive. It protects walking the *_fsnotify_marks lists.
* However, if we do not walk the lists, we do not have to do
* SRCU because we have no references to any objects and do not
* need SRCU to keep them "alive".
*/
if (!sb->s_fsnotify_marks &&
(!mnt || !mnt->mnt_fsnotify_marks) &&
(!inode || !inode->i_fsnotify_marks) &&
(!inode2 || !inode2->i_fsnotify_marks))
return 0;
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
marks_mask = sb->s_fsnotify_mask;
if (mnt)
marks_mask |= mnt->mnt_fsnotify_mask;
if (inode)
marks_mask |= inode->i_fsnotify_mask;
if (inode2)
marks_mask |= inode2->i_fsnotify_mask;
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
/*
fsnotify: optimize FS_MODIFY events with no ignored masks fsnotify() treats FS_MODIFY events specially - it does not skip them even if the FS_MODIFY event does not apear in the object's fsnotify mask. This is because send_to_group() checks if FS_MODIFY needs to clear ignored mask of marks. The common case is that an object does not have any mark with ignored mask and in particular, that it does not have a mark with ignored mask and without the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag. Set FS_MODIFY in object's fsnotify mask during fsnotify_recalc_mask() if object has a mark with an ignored mask and without the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag and remove the special treatment of FS_MODIFY in fsnotify(), so that FS_MODIFY events could be optimized in the common case. Call fsnotify_recalc_mask() from fanotify after adding or removing an ignored mask from a mark without FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY or when adding the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag to a mark with ignored mask (the flag cannot be removed by fanotify uapi). Performance results for doing 10000000 write(2)s to tmpfs: vanilla patched without notification mark 25.486+-1.054 24.965+-0.244 with notification mark 30.111+-0.139 26.891+-1.355 So we can see the overhead of notification subsystem has been drastically reduced. Link: https://lore.kernel.org/r/20220223151438.790268-3-amir73il@gmail.com Suggested-by: Jan Kara <jack@suse.cz> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2022-02-23 15:14:38 +00:00
* If this is a modify event we may need to clear some ignored masks.
* In that case, the object with ignored masks will have the FS_MODIFY
* event in its mask.
* Otherwise, return if none of the marks care about this type of event.
*/
fsnotify: Rearrange fast path to minimise overhead when there is no watcher The fsnotify paths are trivial to hit even when there are no watchers and they are surprisingly expensive. For example, every successful vfs_write() hits fsnotify_modify which calls both fsnotify_parent and fsnotify unless FMODE_NONOTIFY is set which is an internal flag invisible to userspace. As it stands, fsnotify_parent is a guaranteed functional call even if there are no watchers and fsnotify() does a substantial amount of unnecessary work before it checks if there are any watchers. A perf profile showed that applying mnt->mnt_fsnotify_mask in fnotify() was almost half of the total samples taken in that function during a test. This patch rearranges the fast paths to reduce the amount of work done when there are no watchers. The test motivating this was "perf bench sched messaging --pipe". Despite the fact the pipes are anonymous, fsnotify is still called a lot and the overhead is noticeable even though it's completely pointless. It's likely the overhead is negligible for real IO so this is an extreme example. This is a comparison of hackbench using processes and pipes on a 1-socket machine with 8 CPU threads without fanotify watchers. 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Amean 1 0.4837 ( 0.00%) 0.4630 * 4.27%* Amean 3 1.5447 ( 0.00%) 1.4557 ( 5.76%) Amean 5 2.6037 ( 0.00%) 2.4363 ( 6.43%) Amean 7 3.5987 ( 0.00%) 3.4757 ( 3.42%) Amean 12 5.8267 ( 0.00%) 5.6983 ( 2.20%) Amean 18 8.4400 ( 0.00%) 8.1327 ( 3.64%) Amean 24 11.0187 ( 0.00%) 10.0290 * 8.98%* Amean 30 13.1013 ( 0.00%) 12.8510 ( 1.91%) Amean 32 13.9190 ( 0.00%) 13.2410 ( 4.87%) 5.7.0 5.7.0 vanilla fastfsnotify-v1r1 Duration User 157.05 152.79 Duration System 1279.98 1219.32 Duration Elapsed 182.81 174.52 This is showing that the latencies are improved by roughly 2-9%. The variability is not shown but some of these results are within the noise as this workload heavily overloads the machine. That said, the system CPU usage is reduced by quite a bit so it makes sense to avoid the overhead even if it is a bit tricky to detect at times. A perf profile of just 1 group of tasks showed that 5.14% of samples taken were in either fsnotify() or fsnotify_parent(). With the patch, 2.8% of samples were in fsnotify, mostly function entry and the initial check for watchers. The check for watchers is complicated enough that inlining it may be controversial. [Amir] Slightly simplify with mnt_or_sb_mask => marks_mask Link: https://lore.kernel.org/r/20200708111156.24659-1-amir73il@gmail.com Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-07-08 11:11:36 +00:00
test_mask = (mask & ALL_FSNOTIFY_EVENTS);
fsnotify: optimize FS_MODIFY events with no ignored masks fsnotify() treats FS_MODIFY events specially - it does not skip them even if the FS_MODIFY event does not apear in the object's fsnotify mask. This is because send_to_group() checks if FS_MODIFY needs to clear ignored mask of marks. The common case is that an object does not have any mark with ignored mask and in particular, that it does not have a mark with ignored mask and without the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag. Set FS_MODIFY in object's fsnotify mask during fsnotify_recalc_mask() if object has a mark with an ignored mask and without the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag and remove the special treatment of FS_MODIFY in fsnotify(), so that FS_MODIFY events could be optimized in the common case. Call fsnotify_recalc_mask() from fanotify after adding or removing an ignored mask from a mark without FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY or when adding the FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY flag to a mark with ignored mask (the flag cannot be removed by fanotify uapi). Performance results for doing 10000000 write(2)s to tmpfs: vanilla patched without notification mark 25.486+-1.054 24.965+-0.244 with notification mark 30.111+-0.139 26.891+-1.355 So we can see the overhead of notification subsystem has been drastically reduced. Link: https://lore.kernel.org/r/20220223151438.790268-3-amir73il@gmail.com Suggested-by: Jan Kara <jack@suse.cz> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2022-02-23 15:14:38 +00:00
if (!(test_mask & marks_mask))
return 0;
iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
iter_info.marks[FSNOTIFY_ITER_TYPE_SB] =
fsnotify_first_mark(&sb->s_fsnotify_marks);
if (mnt) {
iter_info.marks[FSNOTIFY_ITER_TYPE_VFSMOUNT] =
fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
}
if (inode) {
iter_info.marks[FSNOTIFY_ITER_TYPE_INODE] =
fsnotify_first_mark(&inode->i_fsnotify_marks);
}
if (inode2) {
iter_info.marks[inode2_type] =
fsnotify_first_mark(&inode2->i_fsnotify_marks);
}
/*
* We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
* ignore masks are properly reflected for mount/sb mark notifications.
* That's why this traversal is so complicated...
*/
while (fsnotify_iter_select_report_types(&iter_info)) {
ret = send_to_group(mask, data, data_type, dir, file_name,
cookie, &iter_info);
if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
goto out;
fsnotify_iter_next(&iter_info);
}
ret = 0;
out:
srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
return ret;
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
}
EXPORT_SYMBOL_GPL(fsnotify);
static __init int fsnotify_init(void)
{
int ret;
BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
ret = init_srcu_struct(&fsnotify_mark_srcu);
if (ret)
panic("initializing fsnotify_mark_srcu");
fsnotify: Move mark list head from object into dedicated structure Currently notification marks are attached to object (inode or vfsmnt) by a hlist_head in the object. The list is also protected by a spinlock in the object. So while there is any mark attached to the list of marks, the object must be pinned in memory (and thus e.g. last iput() deleting inode cannot happen). Also for list iteration in fsnotify() to work, we must hold fsnotify_mark_srcu lock so that mark itself and mark->obj_list.next cannot get freed. Thus we are required to wait for response to fanotify events from userspace process with fsnotify_mark_srcu lock held. That causes issues when userspace process is buggy and does not reply to some event - basically the whole notification subsystem gets eventually stuck. So to be able to drop fsnotify_mark_srcu lock while waiting for response, we have to pin the mark in memory and make sure it stays in the object list (as removing the mark waiting for response could lead to lost notification events for groups later in the list). However we don't want inode reclaim to block on such mark as that would lead to system just locking up elsewhere. This commit is the first in the series that paves way towards solving these conflicting lifetime needs. Instead of anchoring the list of marks directly in the object, we anchor it in a dedicated structure (fsnotify_mark_connector) and just point to that structure from the object. The following commits will also add spinlock protecting the list and object pointer to the structure. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2017-03-14 11:31:02 +00:00
fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
SLAB_PANIC);
return 0;
fsnotify: unified filesystem notification backend fsnotify is a backend for filesystem notification. fsnotify does not provide any userspace interface but does provide the basis needed for other notification schemes such as dnotify. fsnotify can be extended to be the backend for inotify or the upcoming fanotify. fsnotify provides a mechanism for "groups" to register for some set of filesystem events and to then deliver those events to those groups for processing. fsnotify has a number of benefits, the first being actually shrinking the size of an inode. Before fsnotify to support both dnotify and inotify an inode had unsigned long i_dnotify_mask; /* Directory notify events */ struct dnotify_struct *i_dnotify; /* for directory notifications */ struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list But with fsnotify this same functionallity (and more) is done with just __u32 i_fsnotify_mask; /* all events for this inode */ struct hlist_head i_fsnotify_mark_entries; /* marks on this inode */ That's right, inotify, dnotify, and fanotify all in 64 bits. We used that much space just in inotify_watches alone, before this patch set. fsnotify object lifetime and locking is MUCH better than what we have today. inotify locking is incredibly complex. See 8f7b0ba1c8539 as an example of what's been busted since inception. inotify needs to know internal semantics of superblock destruction and unmounting to function. The inode pinning and vfs contortions are horrible. no fsnotify implementers do allocation under locks. This means things like f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to GFP_NOFS can be reverted. There are no longer any allocation rules when using or implementing your own fsnotify listener. fsnotify paves the way for fanotify. In brief fanotify is a notification mechanism that delivers the lisener both an 'event' and an open file descriptor to the object in question. This means that fanotify is pathname agnostic. Some on lkml may not care for the original companies or users that pushed for TALPA, but fanotify was designed with flexibility and input for other users in mind. The readahead group expressed interest in fanotify as it could be used to profile disk access on boot without breaking the audit system. The desktop search groups have also expressed interest in fanotify as it solves a number of the race conditions and problems present with managing inotify when more than a limited number of specific files are of interest. fanotify can provide for a userspace access control system which makes it a clean interface for AV vendors to hook without trying to do binary patching on the syscall table, LSM, and everywhere else they do their things today. With this patch series fanotify can be implemented in less than 1200 lines of easy to review code. Almost all of which is the socket based user interface. This patch series builds fsnotify to the point that it can implement dnotify and inotify_user. Patches exist and will be sent soon after acceptance to finish the in kernel inotify conversion (audit) and implement fanotify. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de>
2009-05-21 21:01:20 +00:00
}
core_initcall(fsnotify_init);