xfs: introduce a xfssyncd workqueue

All of the work xfssyncd does is background functionality. There is
no need for a thread per filesystem to do this work - it can al be
managed by a global workqueue now they manage concurrency
effectively.

Introduce a new gglobal xfssyncd workqueue, and convert the periodic
work to use this new functionality. To do this, use a delayed work
construct to schedule the next running of the periodic sync work
for the filesystem. When the sync work is complete, queue a new
delayed work for the next running of the sync work.

For laptop mode, we wait on completion for the sync works, so ensure
that the sync work queuing interface can flush and wait for work to
complete to enable the work queue infrastructure to replace the
current sequence number and wakeup that is used.

Because the sync work does non-trivial amounts of work, mark the
new work queue as CPU intensive.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index a62e8971539d..2c11e62be888 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -203,12 +203,10 @@ typedef struct xfs_mount {
         struct mutex            m_icsb_mutex;   /* balancer sync lock */
 #endif
         struct xfs_mru_cache    *m_filestream;  /* per-mount filestream data */
+        struct delayed_work     m_sync_work;    /* background sync work */
         struct task_struct      *m_sync_task;   /* generalised sync thread */
-        xfs_sync_work_t         m_sync_work;    /* work item for VFS_SYNC */
         struct list_head        m_sync_list;    /* sync thread work item list */
         spinlock_t              m_sync_lock;    /* work item list lock */
-        int                     m_sync_seq;     /* sync thread generation no. */
-        wait_queue_head_t       m_wait_single_sync_task;
         __int64_t               m_update_flags; /* sb flags we need to update
                                                    on the next remount,rw */
         struct shrinker         m_inode_shrink; /* inode reclaim shrinker */