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

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: default 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

fs/notify/mark.c

+48 −48
Original line number Diff line number Diff line
@@ -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 (iter_info->inode_mark) {

	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;



		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)

{

	/* 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;

		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);

}



/*