linux/fs/notify/mark.c
Amir Goldstein 5b8fea65d1 fanotify: configurable limits via sysfs
fanotify has some hardcoded limits. The only APIs to escape those limits
are FAN_UNLIMITED_QUEUE and FAN_UNLIMITED_MARKS.

Allow finer grained tuning of the system limits via sysfs tunables under
/proc/sys/fs/fanotify, similar to tunables under /proc/sys/fs/inotify,
with some minor differences.

- max_queued_events - global system tunable for group queue size limit.
  Like the inotify tunable with the same name, it defaults to 16384 and
  applies on initialization of a new group.

- max_user_marks - user ns tunable for marks limit per user.
  Like the inotify tunable named max_user_watches, on a machine with
  sufficient RAM and it defaults to 1048576 in init userns and can be
  further limited per containing user ns.

- max_user_groups - user ns tunable for number of groups per user.
  Like the inotify tunable named max_user_instances, it defaults to 128
  in init userns and can be further limited per containing user ns.

The slightly different tunable names used for fanotify are derived from
the "group" and "mark" terminology used in the fanotify man pages and
throughout the code.

Considering the fact that the default value for max_user_instances was
increased in kernel v5.10 from 8192 to 1048576, leaving the legacy
fanotify limit of 8192 marks per group in addition to the max_user_marks
limit makes little sense, so the per group marks limit has been removed.

Note that when a group is initialized with FAN_UNLIMITED_MARKS, its own
marks are not accounted in the per user marks account, so in effect the
limit of max_user_marks is only for the collection of groups that are
not initialized with FAN_UNLIMITED_MARKS.

Link: https://lore.kernel.org/r/20210304112921.3996419-2-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>
2021-03-16 16:49:31 +01:00

846 lines
25 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*/
/*
* fsnotify inode mark locking/lifetime/and refcnting
*
* REFCNT:
* The group->recnt and mark->refcnt tell how many "things" in the kernel
* currently are referencing the objects. Both kind of objects typically will
* live inside the kernel with a refcnt of 2, one for its creation and one for
* the reference a group and a mark hold to each other.
* If you are holding the appropriate locks, you can take a reference and the
* object itself is guaranteed to survive until the reference is dropped.
*
* LOCKING:
* There are 3 locks involved with fsnotify inode marks and they MUST be taken
* in order as follows:
*
* group->mark_mutex
* mark->lock
* mark->connector->lock
*
* group->mark_mutex protects the marks_list anchored inside a given group and
* each mark is hooked via the g_list. It also protects the groups private
* data (i.e group limits).
* mark->lock protects the marks attributes like its masks and flags.
* Furthermore it protects the access to a reference of the group that the mark
* is assigned to as well as the access to a reference of the inode/vfsmount
* that is being watched by the mark.
*
* mark->connector->lock protects the list of marks anchored inside an
* inode / vfsmount and each mark is hooked via the i_list.
*
* A list of notification marks relating to inode / mnt is contained in
* fsnotify_mark_connector. That structure is alive as long as there are any
* marks in the list and is also protected by fsnotify_mark_srcu. A mark gets
* detached from fsnotify_mark_connector when last reference to the mark is
* dropped. Thus having mark reference is enough to protect mark->connector
* pointer and to make sure fsnotify_mark_connector cannot disappear. Also
* because we remove mark from g_list before dropping mark reference associated
* with that, any mark found through g_list is guaranteed to have
* mark->connector set until we drop group->mark_mutex.
*
* LIFETIME:
* Inode marks survive between when they are added to an inode and when their
* refcnt==0. Marks are also protected by fsnotify_mark_srcu.
*
* The inode mark can be cleared for a number of different reasons including:
* - The inode is unlinked for the last time. (fsnotify_inode_remove)
* - The inode is being evicted from cache. (fsnotify_inode_delete)
* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
* - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
* - The fsnotify_group associated with the mark is going away and all such marks
* need to be cleaned up. (fsnotify_clear_marks_by_group)
*
* This has the very interesting property of being able to run concurrently with
* any (or all) other directions.
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/srcu.h>
#include <linux/ratelimit.h>
#include <linux/atomic.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
#define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */
struct srcu_struct fsnotify_mark_srcu;
struct kmem_cache *fsnotify_mark_connector_cachep;
static DEFINE_SPINLOCK(destroy_lock);
static LIST_HEAD(destroy_list);
static struct fsnotify_mark_connector *connector_destroy_list;
static void fsnotify_mark_destroy_workfn(struct work_struct *work);
static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
static void fsnotify_connector_destroy_workfn(struct work_struct *work);
static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
void fsnotify_get_mark(struct fsnotify_mark *mark)
{
WARN_ON_ONCE(!refcount_read(&mark->refcnt));
refcount_inc(&mark->refcnt);
}
static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
{
if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
return NULL;
}
__u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
{
if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
return 0;
return *fsnotify_conn_mask_p(conn);
}
static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
{
u32 new_mask = 0;
struct fsnotify_mark *mark;
assert_spin_locked(&conn->lock);
/* We can get detached connector here when inode is getting unlinked. */
if (!fsnotify_valid_obj_type(conn->type))
return;
hlist_for_each_entry(mark, &conn->list, obj_list) {
if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)
new_mask |= mark->mask;
}
*fsnotify_conn_mask_p(conn) = new_mask;
}
/*
* Calculate mask of events for a list of marks. The caller must make sure
* connector and connector->obj cannot disappear under us. Callers achieve
* this by holding a mark->lock or mark->group->mark_mutex for a mark on this
* list.
*/
void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
{
if (!conn)
return;
spin_lock(&conn->lock);
__fsnotify_recalc_mask(conn);
spin_unlock(&conn->lock);
if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
__fsnotify_update_child_dentry_flags(
fsnotify_conn_inode(conn));
}
/* Free all connectors queued for freeing once SRCU period ends */
static void fsnotify_connector_destroy_workfn(struct work_struct *work)
{
struct fsnotify_mark_connector *conn, *free;
spin_lock(&destroy_lock);
conn = connector_destroy_list;
connector_destroy_list = NULL;
spin_unlock(&destroy_lock);
synchronize_srcu(&fsnotify_mark_srcu);
while (conn) {
free = conn;
conn = conn->destroy_next;
kmem_cache_free(fsnotify_mark_connector_cachep, free);
}
}
static void *fsnotify_detach_connector_from_object(
struct fsnotify_mark_connector *conn,
unsigned int *type)
{
struct inode *inode = NULL;
*type = conn->type;
if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
return NULL;
if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
inode = fsnotify_conn_inode(conn);
inode->i_fsnotify_mask = 0;
atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
} else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
} else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
}
rcu_assign_pointer(*(conn->obj), NULL);
conn->obj = NULL;
conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
return inode;
}
static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
{
struct fsnotify_group *group = mark->group;
if (WARN_ON_ONCE(!group))
return;
group->ops->free_mark(mark);
fsnotify_put_group(group);
}
/* Drop object reference originally held by a connector */
static void fsnotify_drop_object(unsigned int type, void *objp)
{
struct inode *inode;
struct super_block *sb;
if (!objp)
return;
/* Currently only inode references are passed to be dropped */
if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
return;
inode = objp;
sb = inode->i_sb;
iput(inode);
if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
wake_up_var(&sb->s_fsnotify_inode_refs);
}
void fsnotify_put_mark(struct fsnotify_mark *mark)
{
struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
void *objp = NULL;
unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
bool free_conn = false;
/* Catch marks that were actually never attached to object */
if (!conn) {
if (refcount_dec_and_test(&mark->refcnt))
fsnotify_final_mark_destroy(mark);
return;
}
/*
* We have to be careful so that traversals of obj_list under lock can
* safely grab mark reference.
*/
if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
return;
hlist_del_init_rcu(&mark->obj_list);
if (hlist_empty(&conn->list)) {
objp = fsnotify_detach_connector_from_object(conn, &type);
free_conn = true;
} else {
__fsnotify_recalc_mask(conn);
}
WRITE_ONCE(mark->connector, NULL);
spin_unlock(&conn->lock);
fsnotify_drop_object(type, objp);
if (free_conn) {
spin_lock(&destroy_lock);
conn->destroy_next = connector_destroy_list;
connector_destroy_list = conn;
spin_unlock(&destroy_lock);
queue_work(system_unbound_wq, &connector_reaper_work);
}
/*
* Note that we didn't update flags telling whether inode cares about
* what's happening with children. We update these flags from
* __fsnotify_parent() lazily when next event happens on one of our
* children.
*/
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
queue_delayed_work(system_unbound_wq, &reaper_work,
FSNOTIFY_REAPER_DELAY);
}
EXPORT_SYMBOL_GPL(fsnotify_put_mark);
/*
* Get mark reference when we found the mark via lockless traversal of object
* list. Mark can be already removed from the list by now and on its way to be
* destroyed once SRCU period ends.
*
* Also pin the group so it doesn't disappear under us.
*/
static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
{
if (!mark)
return true;
if (refcount_inc_not_zero(&mark->refcnt)) {
spin_lock(&mark->lock);
if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
/* mark is attached, group is still alive then */
atomic_inc(&mark->group->user_waits);
spin_unlock(&mark->lock);
return true;
}
spin_unlock(&mark->lock);
fsnotify_put_mark(mark);
}
return false;
}
/*
* Puts marks and wakes up group destruction if necessary.
*
* Pairs with fsnotify_get_mark_safe()
*/
static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
{
if (mark) {
struct fsnotify_group *group = mark->group;
fsnotify_put_mark(mark);
/*
* We abuse notification_waitq on group shutdown for waiting for
* all marks pinned when waiting for userspace.
*/
if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
wake_up(&group->notification_waitq);
}
}
bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
__releases(&fsnotify_mark_srcu)
{
int type;
fsnotify_foreach_obj_type(type) {
/* This can fail if mark is being removed */
if (!fsnotify_get_mark_safe(iter_info->marks[type])) {
__release(&fsnotify_mark_srcu);
goto fail;
}
}
/*
* Now that both marks are pinned by refcount in the inode / vfsmount
* lists, we can drop SRCU lock, and safely resume the list iteration
* once userspace returns.
*/
srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
return true;
fail:
for (type--; type >= 0; type--)
fsnotify_put_mark_wake(iter_info->marks[type]);
return false;
}
void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
__acquires(&fsnotify_mark_srcu)
{
int type;
iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
fsnotify_foreach_obj_type(type)
fsnotify_put_mark_wake(iter_info->marks[type]);
}
/*
* Mark mark as detached, remove it from group list. Mark still stays in object
* list until its last reference is dropped. Note that we rely on mark being
* removed from group list before corresponding reference to it is dropped. In
* particular we rely on mark->connector being valid while we hold
* group->mark_mutex if we found the mark through g_list.
*
* Must be called with group->mark_mutex held. The caller must either hold
* reference to the mark or be protected by fsnotify_mark_srcu.
*/
void fsnotify_detach_mark(struct fsnotify_mark *mark)
{
struct fsnotify_group *group = mark->group;
WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
refcount_read(&mark->refcnt) < 1 +
!!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
spin_lock(&mark->lock);
/* something else already called this function on this mark */
if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
spin_unlock(&mark->lock);
return;
}
mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
list_del_init(&mark->g_list);
spin_unlock(&mark->lock);
/* Drop mark reference acquired in fsnotify_add_mark_locked() */
fsnotify_put_mark(mark);
}
/*
* Free fsnotify mark. The mark is actually only marked as being freed. The
* freeing is actually happening only once last reference to the mark is
* dropped from a workqueue which first waits for srcu period end.
*
* Caller must have a reference to the mark or be protected by
* fsnotify_mark_srcu.
*/
void fsnotify_free_mark(struct fsnotify_mark *mark)
{
struct fsnotify_group *group = mark->group;
spin_lock(&mark->lock);
/* something else already called this function on this mark */
if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
spin_unlock(&mark->lock);
return;
}
mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
spin_unlock(&mark->lock);
/*
* Some groups like to know that marks are being freed. This is a
* callback to the group function to let it know that this mark
* is being freed.
*/
if (group->ops->freeing_mark)
group->ops->freeing_mark(mark, group);
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group)
{
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
fsnotify_free_mark(mark);
}
EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
/*
* Sorting function for lists of fsnotify marks.
*
* Fanotify supports different notification classes (reflected as priority of
* notification group). Events shall be passed to notification groups in
* decreasing priority order. To achieve this marks in notification lists for
* inodes and vfsmounts are sorted so that priorities of corresponding groups
* are descending.
*
* Furthermore correct handling of the ignore mask requires processing inode
* and vfsmount marks of each group together. Using the group address as
* further sort criterion provides a unique sorting order and thus we can
* merge inode and vfsmount lists of marks in linear time and find groups
* present in both lists.
*
* A return value of 1 signifies that b has priority over a.
* A return value of 0 signifies that the two marks have to be handled together.
* A return value of -1 signifies that a has priority over b.
*/
int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
{
if (a == b)
return 0;
if (!a)
return 1;
if (!b)
return -1;
if (a->priority < b->priority)
return 1;
if (a->priority > b->priority)
return -1;
if (a < b)
return 1;
return -1;
}
static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
unsigned int type,
__kernel_fsid_t *fsid)
{
struct inode *inode = NULL;
struct fsnotify_mark_connector *conn;
conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
if (!conn)
return -ENOMEM;
spin_lock_init(&conn->lock);
INIT_HLIST_HEAD(&conn->list);
conn->type = type;
conn->obj = connp;
/* Cache fsid of filesystem containing the object */
if (fsid) {
conn->fsid = *fsid;
conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
} else {
conn->fsid.val[0] = conn->fsid.val[1] = 0;
conn->flags = 0;
}
if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
inode = igrab(fsnotify_conn_inode(conn));
/*
* cmpxchg() provides the barrier so that readers of *connp can see
* only initialized structure
*/
if (cmpxchg(connp, NULL, conn)) {
/* Someone else created list structure for us */
if (inode)
iput(inode);
kmem_cache_free(fsnotify_mark_connector_cachep, conn);
}
return 0;
}
/*
* Get mark connector, make sure it is alive and return with its lock held.
* This is for users that get connector pointer from inode or mount. Users that
* hold reference to a mark on the list may directly lock connector->lock as
* they are sure list cannot go away under them.
*/
static struct fsnotify_mark_connector *fsnotify_grab_connector(
fsnotify_connp_t *connp)
{
struct fsnotify_mark_connector *conn;
int idx;
idx = srcu_read_lock(&fsnotify_mark_srcu);
conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
if (!conn)
goto out;
spin_lock(&conn->lock);
if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
spin_unlock(&conn->lock);
srcu_read_unlock(&fsnotify_mark_srcu, idx);
return NULL;
}
out:
srcu_read_unlock(&fsnotify_mark_srcu, idx);
return conn;
}
/*
* Add mark into proper place in given list of marks. These marks may be used
* for the fsnotify backend to determine which event types should be delivered
* to which group and for which inodes. These marks are ordered according to
* priority, highest number first, and then by the group's location in memory.
*/
static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
fsnotify_connp_t *connp, unsigned int type,
int allow_dups, __kernel_fsid_t *fsid)
{
struct fsnotify_mark *lmark, *last = NULL;
struct fsnotify_mark_connector *conn;
int cmp;
int err = 0;
if (WARN_ON(!fsnotify_valid_obj_type(type)))
return -EINVAL;
/* Backend is expected to check for zero fsid (e.g. tmpfs) */
if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
return -ENODEV;
restart:
spin_lock(&mark->lock);
conn = fsnotify_grab_connector(connp);
if (!conn) {
spin_unlock(&mark->lock);
err = fsnotify_attach_connector_to_object(connp, type, fsid);
if (err)
return err;
goto restart;
} else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
conn->fsid = *fsid;
/* Pairs with smp_rmb() in fanotify_get_fsid() */
smp_wmb();
conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
} else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
(fsid->val[0] != conn->fsid.val[0] ||
fsid->val[1] != conn->fsid.val[1])) {
/*
* Backend is expected to check for non uniform fsid
* (e.g. btrfs), but maybe we missed something?
* Only allow setting conn->fsid once to non zero fsid.
* inotify and non-fid fanotify groups do not set nor test
* conn->fsid.
*/
pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
"%x.%x != %x.%x\n", __func__, conn->type,
fsid->val[0], fsid->val[1],
conn->fsid.val[0], conn->fsid.val[1]);
err = -EXDEV;
goto out_err;
}
/* is mark the first mark? */
if (hlist_empty(&conn->list)) {
hlist_add_head_rcu(&mark->obj_list, &conn->list);
goto added;
}
/* should mark be in the middle of the current list? */
hlist_for_each_entry(lmark, &conn->list, obj_list) {
last = lmark;
if ((lmark->group == mark->group) &&
(lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
!allow_dups) {
err = -EEXIST;
goto out_err;
}
cmp = fsnotify_compare_groups(lmark->group, mark->group);
if (cmp >= 0) {
hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
goto added;
}
}
BUG_ON(last == NULL);
/* mark should be the last entry. last is the current last entry */
hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
added:
/*
* Since connector is attached to object using cmpxchg() we are
* guaranteed that connector initialization is fully visible by anyone
* seeing mark->connector set.
*/
WRITE_ONCE(mark->connector, conn);
out_err:
spin_unlock(&conn->lock);
spin_unlock(&mark->lock);
return err;
}
/*
* Attach an initialized mark to a given group and fs object.
* These marks may be used for the fsnotify backend to determine which
* event types should be delivered to which group.
*/
int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
fsnotify_connp_t *connp, unsigned int type,
int allow_dups, __kernel_fsid_t *fsid)
{
struct fsnotify_group *group = mark->group;
int ret = 0;
BUG_ON(!mutex_is_locked(&group->mark_mutex));
/*
* LOCKING ORDER!!!!
* group->mark_mutex
* mark->lock
* mark->connector->lock
*/
spin_lock(&mark->lock);
mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
list_add(&mark->g_list, &group->marks_list);
fsnotify_get_mark(mark); /* for g_list */
spin_unlock(&mark->lock);
ret = fsnotify_add_mark_list(mark, connp, type, allow_dups, fsid);
if (ret)
goto err;
if (mark->mask)
fsnotify_recalc_mask(mark->connector);
return ret;
err:
spin_lock(&mark->lock);
mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
FSNOTIFY_MARK_FLAG_ATTACHED);
list_del_init(&mark->g_list);
spin_unlock(&mark->lock);
fsnotify_put_mark(mark);
return ret;
}
int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
unsigned int type, int allow_dups, __kernel_fsid_t *fsid)
{
int ret;
struct fsnotify_group *group = mark->group;
mutex_lock(&group->mark_mutex);
ret = fsnotify_add_mark_locked(mark, connp, type, allow_dups, fsid);
mutex_unlock(&group->mark_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(fsnotify_add_mark);
/*
* Given a list of marks, find the mark associated with given group. If found
* take a reference to that mark and return it, else return NULL.
*/
struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
struct fsnotify_group *group)
{
struct fsnotify_mark_connector *conn;
struct fsnotify_mark *mark;
conn = fsnotify_grab_connector(connp);
if (!conn)
return NULL;
hlist_for_each_entry(mark, &conn->list, obj_list) {
if (mark->group == group &&
(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
fsnotify_get_mark(mark);
spin_unlock(&conn->lock);
return mark;
}
}
spin_unlock(&conn->lock);
return NULL;
}
EXPORT_SYMBOL_GPL(fsnotify_find_mark);
/* Clear any marks in a group with given type mask */
void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
unsigned int type_mask)
{
struct fsnotify_mark *lmark, *mark;
LIST_HEAD(to_free);
struct list_head *head = &to_free;
/* Skip selection step if we want to clear all marks. */
if (type_mask == FSNOTIFY_OBJ_ALL_TYPES_MASK) {
head = &group->marks_list;
goto clear;
}
/*
* We have to be really careful here. Anytime we drop mark_mutex, e.g.
* fsnotify_clear_marks_by_inode() can come and free marks. Even in our
* to_free list so we have to use mark_mutex even when accessing that
* list. And freeing mark requires us to drop mark_mutex. So we can
* reliably free only the first mark in the list. That's why we first
* move marks to free to to_free list in one go and then free marks in
* to_free list one by one.
*/
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
if ((1U << mark->connector->type) & type_mask)
list_move(&mark->g_list, &to_free);
}
mutex_unlock(&group->mark_mutex);
clear:
while (1) {
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
if (list_empty(head)) {
mutex_unlock(&group->mark_mutex);
break;
}
mark = list_first_entry(head, struct fsnotify_mark, g_list);
fsnotify_get_mark(mark);
fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
fsnotify_free_mark(mark);
fsnotify_put_mark(mark);
}
}
/* Destroy all marks attached to an object via connector */
void fsnotify_destroy_marks(fsnotify_connp_t *connp)
{
struct fsnotify_mark_connector *conn;
struct fsnotify_mark *mark, *old_mark = NULL;
void *objp;
unsigned int type;
conn = fsnotify_grab_connector(connp);
if (!conn)
return;
/*
* We have to be careful since we can race with e.g.
* fsnotify_clear_marks_by_group() and once we drop the conn->lock, the
* list can get modified. However we are holding mark reference and
* thus our mark cannot be removed from obj_list so we can continue
* iteration after regaining conn->lock.
*/
hlist_for_each_entry(mark, &conn->list, obj_list) {
fsnotify_get_mark(mark);
spin_unlock(&conn->lock);
if (old_mark)
fsnotify_put_mark(old_mark);
old_mark = mark;
fsnotify_destroy_mark(mark, mark->group);
spin_lock(&conn->lock);
}
/*
* Detach list from object now so that we don't pin inode until all
* mark references get dropped. It would lead to strange results such
* as delaying inode deletion or blocking unmount.
*/
objp = fsnotify_detach_connector_from_object(conn, &type);
spin_unlock(&conn->lock);
if (old_mark)
fsnotify_put_mark(old_mark);
fsnotify_drop_object(type, objp);
}
/*
* Nothing fancy, just initialize lists and locks and counters.
*/
void fsnotify_init_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group)
{
memset(mark, 0, sizeof(*mark));
spin_lock_init(&mark->lock);
refcount_set(&mark->refcnt, 1);
fsnotify_get_group(group);
mark->group = group;
WRITE_ONCE(mark->connector, NULL);
}
EXPORT_SYMBOL_GPL(fsnotify_init_mark);
/*
* Destroy all marks in destroy_list, waits for SRCU period to finish before
* actually freeing marks.
*/
static void fsnotify_mark_destroy_workfn(struct work_struct *work)
{
struct fsnotify_mark *mark, *next;
struct list_head private_destroy_list;
spin_lock(&destroy_lock);
/* exchange the list head */
list_replace_init(&destroy_list, &private_destroy_list);
spin_unlock(&destroy_lock);
synchronize_srcu(&fsnotify_mark_srcu);
list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
list_del_init(&mark->g_list);
fsnotify_final_mark_destroy(mark);
}
}
/* Wait for all marks queued for destruction to be actually destroyed */
void fsnotify_wait_marks_destroyed(void)
{
flush_delayed_work(&reaper_work);
}
EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);