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authorBrian Foster <bfoster@redhat.com>2014-11-28 13:59:58 +1100
committerDave Chinner <david@fromorbit.com>2014-11-28 13:59:58 +1100
commit78c931b8be75456562b55ed4e27878f1519e1367 (patch)
treea3a3b996307a11f0b292f734416da70f6622532b /fs/xfs/xfs_mount.h
parentcac7f2429872d3733dc3f9915857b1691da2eb2f (diff)
xfs: replace global xfslogd wq with per-mount wq
The xfslogd workqueue is a global, single-job workqueue for buffer ioend processing. This means we allow for a single work item at a time for all possible XFS mounts on a system. fsstress testing in loopback XFS over XFS configurations has reproduced xfslogd deadlocks due to the single threaded nature of the queue and dependencies introduced between the separate XFS instances by online discard (-o discard). Discard over a loopback device converts the discard request to a hole punch (fallocate) on the underlying file. Online discard requests are issued synchronously and from xfslogd context in XFS, hence the xfslogd workqueue is blocked in the upper fs waiting on a hole punch request to be servied in the lower fs. If the lower fs issues I/O that depends on xfslogd to complete, both filesystems end up hung indefinitely. This is reproduced reliabily by generic/013 on XFS->loop->XFS test devices with the '-o discard' mount option. Further, docker implementations appear to use this kind of configuration for container instance filesystems by default (container fs->dm-> loop->base fs) and therefore are subject to this deadlock when running on XFS. Replace the global xfslogd workqueue with a per-mount variant. This guarantees each mount access to a single worker and prevents deadlocks due to inter-fs dependencies introduced by discard. Since the queue is only responsible for buffer iodone processing at this point in time, rename xfslogd to xfs-buf. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_mount.h')
-rw-r--r--fs/xfs/xfs_mount.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index b0447c86e7e2..394bc711171a 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -168,6 +168,7 @@ typedef struct xfs_mount {
/* low free space thresholds */
struct xfs_kobj m_kobj;
+ struct workqueue_struct *m_buf_workqueue;
struct workqueue_struct *m_data_workqueue;
struct workqueue_struct *m_unwritten_workqueue;
struct workqueue_struct *m_cil_workqueue;