Commit 24c20305 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Jan Kara

fsnotify: clean up fsnotify_prepare/finish_user_wait()

This patch doesn't actually fix any bug, just paves the way for fixing mark
and group pinning.
Reviewed-by: Amir Goldstein's avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v4.12
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 7761daa6
......@@ -109,16 +109,6 @@ void fsnotify_get_mark(struct fsnotify_mark *mark)
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;
......@@ -256,32 +246,63 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
FSNOTIFY_REAPER_DELAY);
}
bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
/*
* 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)
{
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;
if (!mark)
return true;
group = 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 (atomic_inc_not_zero(&mark->refcnt))
return true;
if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
wake_up(&group->notification_waitq);
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;
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;
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);
}
if (iter_info->vfsmount_mark) {
if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark))
goto out_inode;
}
bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
{
/* This can fail if mark is being removed */
if (!fsnotify_get_mark_safe(iter_info->inode_mark))
return false;
if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark)) {
fsnotify_put_mark_wake(iter_info->inode_mark);
return false;
}
/*
......@@ -292,34 +313,13 @@ bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
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);
fsnotify_put_mark_wake(iter_info->inode_mark);
fsnotify_put_mark_wake(iter_info->vfsmount_mark);
}
/*
......
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