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Subject[PATCH 4.14 080/193] fsnotify: clean up fsnotify_prepare/finish_user_wait()
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@redhat.com>

commit 24c20305c7fc8959836211cb8c50aab93ae0e54f upstream.

This patch doesn't actually fix any bug, just paves the way for fixing mark
and group pinning.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/notify/mark.c | 98 +++++++++++++++++++++++++++----------------------------
1 file changed, 49 insertions(+), 49 deletions(-)

--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -109,16 +109,6 @@ void fsnotify_get_mark(struct fsnotify_m
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_m
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;
- }
- if (iter_info->vfsmount_mark) {
- if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark))
- goto out_inode;
+ 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))
+ 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 f
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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