linux/fs/notify/mark.c
Dan Carpenter f4edce1afd fsnotify: remove a stray unlock
We recently shifted this code around, so we're no longer holding the
lock on this path.

Fixes: 755b5bc681 ("fsnotify: Remove indirection from mark list addition")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
2017-04-24 16:41:28 +02:00

773 lines
23 KiB
C

/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* 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/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(!atomic_read(&mark->refcnt));
atomic_inc(&mark->refcnt);
}
/*
* 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.
*/
static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
{
return atomic_inc_not_zero(&mark->refcnt);
}
static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
{
u32 new_mask = 0;
struct fsnotify_mark *mark;
assert_spin_locked(&conn->lock);
hlist_for_each_entry(mark, &conn->list, obj_list) {
if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)
new_mask |= mark->mask;
}
if (conn->flags & FSNOTIFY_OBJ_TYPE_INODE)
conn->inode->i_fsnotify_mask = new_mask;
else if (conn->flags & FSNOTIFY_OBJ_TYPE_VFSMOUNT)
real_mount(conn->mnt)->mnt_fsnotify_mask = new_mask;
}
/*
* Calculate mask of events for a list of marks. The caller must make sure
* connector and connector->inode 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->flags & FSNOTIFY_OBJ_TYPE_INODE)
__fsnotify_update_child_dentry_flags(conn->inode);
}
/* 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 struct inode *fsnotify_detach_connector_from_object(
struct fsnotify_mark_connector *conn)
{
struct inode *inode = NULL;
if (conn->flags & FSNOTIFY_OBJ_TYPE_INODE) {
inode = conn->inode;
rcu_assign_pointer(inode->i_fsnotify_marks, NULL);
inode->i_fsnotify_mask = 0;
conn->inode = NULL;
conn->flags &= ~FSNOTIFY_OBJ_TYPE_INODE;
} else if (conn->flags & FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
rcu_assign_pointer(real_mount(conn->mnt)->mnt_fsnotify_marks,
NULL);
real_mount(conn->mnt)->mnt_fsnotify_mask = 0;
conn->mnt = NULL;
conn->flags &= ~FSNOTIFY_OBJ_TYPE_VFSMOUNT;
}
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);
}
void fsnotify_put_mark(struct fsnotify_mark *mark)
{
struct fsnotify_mark_connector *conn;
struct inode *inode = NULL;
bool free_conn = false;
/* Catch marks that were actually never attached to object */
if (!mark->connector) {
if (atomic_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 (!atomic_dec_and_lock(&mark->refcnt, &mark->connector->lock))
return;
conn = mark->connector;
hlist_del_init_rcu(&mark->obj_list);
if (hlist_empty(&conn->list)) {
inode = fsnotify_detach_connector_from_object(conn);
free_conn = true;
} else {
__fsnotify_recalc_mask(conn);
}
mark->connector = NULL;
spin_unlock(&conn->lock);
iput(inode);
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);
}
bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
{
struct fsnotify_group *group;
if (WARN_ON_ONCE(!iter_info->inode_mark && !iter_info->vfsmount_mark))
return false;
if (iter_info->inode_mark)
group = iter_info->inode_mark->group;
else
group = iter_info->vfsmount_mark->group;
/*
* Since acquisition of mark reference is an atomic op as well, we can
* be sure this inc is seen before any effect of refcount increment.
*/
atomic_inc(&group->user_waits);
if (iter_info->inode_mark) {
/* This can fail if mark is being removed */
if (!fsnotify_get_mark_safe(iter_info->inode_mark))
goto out_wait;
}
if (iter_info->vfsmount_mark) {
if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark))
goto out_inode;
}
/*
* 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;
out_inode:
if (iter_info->inode_mark)
fsnotify_put_mark(iter_info->inode_mark);
out_wait:
if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
wake_up(&group->notification_waitq);
return false;
}
void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
{
struct fsnotify_group *group = NULL;
iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
if (iter_info->inode_mark) {
group = iter_info->inode_mark->group;
fsnotify_put_mark(iter_info->inode_mark);
}
if (iter_info->vfsmount_mark) {
group = iter_info->vfsmount_mark->group;
fsnotify_put_mark(iter_info->vfsmount_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);
}
/*
* 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) &&
atomic_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);
atomic_dec(&group->num_marks);
/* 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);
}
/*
* 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(
struct fsnotify_mark_connector __rcu **connp,
struct inode *inode,
struct vfsmount *mnt)
{
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);
if (inode) {
conn->flags = FSNOTIFY_OBJ_TYPE_INODE;
conn->inode = igrab(inode);
} else {
conn->flags = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
conn->mnt = mnt;
}
/*
* 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(
struct fsnotify_mark_connector __rcu **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->flags & (FSNOTIFY_OBJ_TYPE_INODE |
FSNOTIFY_OBJ_TYPE_VFSMOUNT))) {
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,
struct inode *inode, struct vfsmount *mnt,
int allow_dups)
{
struct fsnotify_mark *lmark, *last = NULL;
struct fsnotify_mark_connector *conn;
struct fsnotify_mark_connector __rcu **connp;
int cmp;
int err = 0;
if (WARN_ON(!inode && !mnt))
return -EINVAL;
if (inode)
connp = &inode->i_fsnotify_marks;
else
connp = &real_mount(mnt)->mnt_fsnotify_marks;
restart:
spin_lock(&mark->lock);
conn = fsnotify_grab_connector(connp);
if (!conn) {
spin_unlock(&mark->lock);
err = fsnotify_attach_connector_to_object(connp, inode, mnt);
if (err)
return err;
goto restart;
}
/* 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:
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, struct inode *inode,
struct vfsmount *mnt, int allow_dups)
{
struct fsnotify_group *group = mark->group;
int ret = 0;
BUG_ON(inode && mnt);
BUG_ON(!inode && !mnt);
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);
atomic_inc(&group->num_marks);
fsnotify_get_mark(mark); /* for g_list */
spin_unlock(&mark->lock);
ret = fsnotify_add_mark_list(mark, inode, mnt, allow_dups);
if (ret)
goto err;
if (mark->mask)
fsnotify_recalc_mask(mark->connector);
return ret;
err:
mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
FSNOTIFY_MARK_FLAG_ATTACHED);
list_del_init(&mark->g_list);
atomic_dec(&group->num_marks);
fsnotify_put_mark(mark);
return ret;
}
int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode,
struct vfsmount *mnt, int allow_dups)
{
int ret;
struct fsnotify_group *group = mark->group;
mutex_lock(&group->mark_mutex);
ret = fsnotify_add_mark_locked(mark, inode, mnt, allow_dups);
mutex_unlock(&group->mark_mutex);
return ret;
}
/*
* 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(
struct fsnotify_mark_connector __rcu **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;
}
/* Clear any marks in a group with given type */
void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
unsigned int type)
{
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 == FSNOTIFY_OBJ_ALL_TYPES) {
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 (mark->connector->flags & type)
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 inode / vfsmount */
void fsnotify_destroy_marks(struct fsnotify_mark_connector __rcu **connp)
{
struct fsnotify_mark_connector *conn;
struct fsnotify_mark *mark, *old_mark = NULL;
struct inode *inode;
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.
*/
inode = fsnotify_detach_connector_from_object(conn);
spin_unlock(&conn->lock);
if (old_mark)
fsnotify_put_mark(old_mark);
iput(inode);
}
/*
* 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);
atomic_set(&mark->refcnt, 1);
fsnotify_get_group(group);
mark->group = group;
}
/*
* 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);
}