Patch "xfs: fix up quotacheck buffer list error handling" has been added to the 3.18-stable tree

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

xfs: fix up quotacheck buffer list error handling

to the 3.18-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:
xfs-fix-up-quotacheck-buffer-list-error-handling.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Brian Foster <[email protected]>
Date: Fri, 21 Apr 2017 12:40:44 -0700
Subject: xfs: fix up quotacheck buffer list error handling

From: Brian Foster <[email protected]>

commit 20e8a063786050083fe05b4f45be338c60b49126 upstream.

The quotacheck error handling of the delwri buffer list assumes the resident buffers are locked and doesn't clear the _XBF_DELWRI_Q flag on the buffers that are dequeued. This can lead to assert failures on buffer release and possibly other locking problems.

Move this code to a delwri queue cancel helper function to encapsulate the logic required to properly release buffers from a delwri queue. Update the helper to clear the delwri queue flag and call it from quotacheck.

---
 fs/xfs/xfs_buf.c |   24 ++++++++++++++++++++++++
 fs/xfs/xfs_buf.h |    1 +
 fs/xfs/xfs_qm.c  |    7 +------
 3 files changed, 26 insertions(+), 6 deletions(-)

@@ -982,6 +982,8 @@ void
 xfs_buf_unlock(
 	struct xfs_buf		*bp)
 {
+	ASSERT(xfs_buf_islocked(bp));
+
 	XB_CLEAR_OWNER(bp);
 	up(&bp->b_sema);
 

@@ -1698,6 +1700,28 @@ error:
 }
 
 /*
+ * Cancel a delayed write list.
+ *
+ * Remove each buffer from the list, clear the delwri queue flag and drop the
+ * associated buffer reference.
+ */
+void
+xfs_buf_delwri_cancel(
+	struct list_head	*list)
+{
+	struct xfs_buf		*bp;
+
+	while (!list_empty(list)) {
+		bp = list_first_entry(list, struct xfs_buf, b_list);
+
+		xfs_buf_lock(bp);
+		bp->b_flags &= ~_XBF_DELWRI_Q;
+		list_del_init(&bp->b_list);
+		xfs_buf_relse(bp);
+	}
+}
+
+/*
  * Add a buffer to the delayed write list.
  *
  * This queues a buffer for writeout if it hasn't already been.  Note that

@@ -302,6 +302,7 @@ extern void xfs_buf_iomove(xfs_buf_t *,
 extern xfs_caddr_t xfs_buf_offset(xfs_buf_t *, size_t);
 
 /* Delayed Write Buffer Routines */
+extern void xfs_buf_delwri_cancel(struct list_head *);
 extern bool xfs_buf_delwri_queue(struct xfs_buf *, struct list_head *);
 extern int xfs_buf_delwri_submit(struct list_head *);
 extern int xfs_buf_delwri_submit_nowait(struct list_head *);

@@ -1359,12 +1359,7 @@ xfs_qm_quotacheck(
 	mp->m_qflags |= flags;
 
  error_return:
-	while (!list_empty(&buffer_list)) {
-		struct xfs_buf *bp =
-			list_first_entry(&buffer_list, struct xfs_buf, b_list);
-		list_del_init(&bp->b_list);
-		xfs_buf_relse(bp);
-	}
+	xfs_buf_delwri_cancel(&buffer_list);
 
 	if (error) {
 		xfs_warn(mp,

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/xfs-fix-missed-holes-in-seek_hole-implementation.patch queue-3.18/xfs-fix-indlen-accounting-error-on-partial-delalloc-conversion.patch queue-3.18/xfs-bad-assertion-for-delalloc-an-extent-that-start-at-i_size.patch queue-3.18/xfs-fix-up-quotacheck-buffer-list-error-handling.patch queue-3.18/xfs-prevent-multi-fsb-dir-readahead-from-reading-random-blocks.patch