Patch "fsnotify: clean up fsnotify_prepare/finish_user_wait()" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    fsnotify: clean up fsnotify_prepare/finish_user_wait()

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fsnotify-clean-up-fsnotify_prepare-finish_user_wait.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 24c20305c7fc8959836211cb8c50aab93ae0e54f Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Mon, 30 Oct 2017 21:14:55 +0100
Subject: fsnotify: clean up fsnotify_prepare/finish_user_wait()

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);
 }
 
 /*


Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.14/fsnotify-clean-up-fsnotify_prepare-finish_user_wait.patch
queue-4.14/fsnotify-fix-pinning-group-in-fsnotify_prepare_user_wait.patch
queue-4.14/fanotify-fix-fsnotify_prepare_user_wait-failure.patch
queue-4.14/fsnotify-pin-both-inode-and-vfsmount-mark.patch
queue-4.14/ovl-put-upperdentry-if-ovl_check_origin-fails.patch