xfs: block callers of xfs_flush_inodes() correctly

xfs_flush_inodes() currently uses a magic timeout to wait for
some inodes to be flushed before returning. This isn't
really reliable but used to be the best that could be done
due to deadlock potential of waiting for the entire flush.

Now the inode flush is safe to execute while we hold page
and inode locks, we can wait for all the inodes to flush
synchronously. Convert the wait mechanism to a completion
to do this efficiently. This should remove all remaining
spurious ENOSPC errors from the delayed allocation reservation
path.

This is extracted almost line for line from a larger patch
from Mikulas Patocka.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

2 files changed, 10 insertions, 3 deletions

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 73cf8dc1973..f7ba76633c2 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -404,7 +404,8 @@ STATIC void
 xfs_syncd_queue_work(
         struct xfs_mount *mp,
         void            *data,
-        void            (*syncer)(struct xfs_mount *, void *))
+        void            (*syncer)(struct xfs_mount *, void *),
+        struct completion *completion)
 {
         struct xfs_sync_work *work;
 
@@ -413,6 +414,7 @@ xfs_syncd_queue_work(
         work->w_syncer = syncer;
         work->w_data = data;
         work->w_mount = mp;
+        work->w_completion = completion;
         spin_lock(&mp->m_sync_lock);
         list_add_tail(&work->w_list, &mp->m_sync_list);
         spin_unlock(&mp->m_sync_lock);
@@ -441,10 +443,11 @@ xfs_flush_inodes(
         xfs_inode_t     *ip)
 {
         struct inode    *inode = VFS_I(ip);
+        DECLARE_COMPLETION_ONSTACK(completion);
 
         igrab(inode);
-        xfs_syncd_queue_work(ip->i_mount, inode, xfs_flush_inodes_work);
-        delay(msecs_to_jiffies(500));
+        xfs_syncd_queue_work(ip->i_mount, inode, xfs_flush_inodes_work, &completion);
+        wait_for_completion(&completion);
         xfs_log_force(ip->i_mount, (xfs_lsn_t)0, XFS_LOG_FORCE|XFS_LOG_SYNC);
 }
 
@@ -514,6 +517,8 @@ xfssyncd(
                         list_del(&work->w_list);
                         if (work == &mp->m_sync_work)
                                 continue;
+                        if (work->w_completion)
+                                complete(work->w_completion);
                         kmem_free(work);
                 }
         }
@@ -527,6 +532,7 @@ xfs_syncd_init(
 {
         mp->m_sync_work.w_syncer = xfs_sync_worker;
         mp->m_sync_work.w_mount = mp;
+        mp->m_sync_work.w_completion = NULL;
         mp->m_sync_task = kthread_run(xfssyncd, mp, "xfssyncd");
         if (IS_ERR(mp->m_sync_task))
                 return -PTR_ERR(mp->m_sync_task);
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index 6e83a35626e..308d5bf6dfb 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -26,6 +26,7 @@ typedef struct xfs_sync_work {
         struct xfs_mount        *w_mount;
         void                    *w_data;        /* syncer routine argument */
         void                    (*w_syncer)(struct xfs_mount *, void *);
+        struct completion       *w_completion;
 } xfs_sync_work_t;
 
 #define SYNC_ATTR               0x0001  /* sync attributes */