[PATCH 4.9 82/94] xfs: fix up quotacheck buffer list error handling

Greg Kroah-Hartman
2017-06-05T16:26:45Z

From: Brian Foster <bfoster@redhat.com>

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.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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(-)

--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1066,6 +1066,8 @@ void
xfs_buf_unlock(
struct xfs_buf *bp)
{
+ ASSERT(xfs_buf_islocked(bp));
+
XB_CLEAR_OWNER(bp);
up(&bp->b_sema);

@@ -1804,6 +1806,28 @@ 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
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -329,6 +329,7 @@ extern void *xfs_buf_offset(struct xfs_b
extern void xfs_buf_stale(struct xfs_buf *bp);

/* 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 *);
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -1384,12 +1384,7 @@ 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,