3 files changed, 34 insertions, 7 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index dab5d3802374..003e5f29d684 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -659,9 +659,17 @@ xfs_fs_sync_super(
         int                     error;
         int                     flags;
 
-        if (unlikely(sb->s_frozen == SB_FREEZE_WRITE))
-                flags = SYNC_QUIESCE;
-        else
+        if (unlikely(sb->s_frozen == SB_FREEZE_WRITE)) {
+                /*
+                 * First stage of freeze - no more writers will make progress
+                 * now we are here, so we flush delwri and delalloc buffers
+                 * here, then wait for all I/O to complete.  Data is frozen at
+                 * that point. Metadata is not frozen, transactions can still
+                 * occur here so don't bother flushing the buftarg (i.e
+                 * SYNC_QUIESCE) because it'll just get dirty again.
+                 */
+                flags = SYNC_FSDATA | SYNC_DELWRI | SYNC_WAIT | SYNC_DIO_WAIT;
+        } else
                 flags = SYNC_FSDATA | (wait ? SYNC_WAIT : 0);
 
         error = bhv_vfs_sync(vfsp, flags, NULL);
diff --git a/fs/xfs/linux-2.6/xfs_vfs.h b/fs/xfs/linux-2.6/xfs_vfs.h
index da255bdf5260..558823a83065 100644
--- a/fs/xfs/linux-2.6/xfs_vfs.h
+++ b/fs/xfs/linux-2.6/xfs_vfs.h
@@ -92,6 +92,7 @@ typedef enum {
 #define SYNC_REFCACHE           0x0040  /* prune some of the nfs ref cache */
 #define SYNC_REMOUNT            0x0080  /* remount readonly, no dummy LRs */
 #define SYNC_QUIESCE            0x0100  /* quiesce fileystem for a snapshot */
+#define SYNC_DIO_WAIT           0x0200  /* wait for direct I/O to complete */
 
 #define SHUTDOWN_META_IO_ERROR  0x0001  /* write attempt to metadata failed */
 #define SHUTDOWN_LOG_IO_ERROR   0x0002  /* write attempt to the log failed */
diff --git a/fs/xfs/xfs_vfsops.c b/fs/xfs/xfs_vfsops.c
index f5ea74b999b6..c2a6eab7fa2d 100644
--- a/fs/xfs/xfs_vfsops.c
+++ b/fs/xfs/xfs_vfsops.c
@@ -872,6 +872,10 @@ xfs_statvfs(
  *                     this by simply making sure the log gets flushed
  *                     if SYNC_BDFLUSH is set, and by actually writing it
  *                     out otherwise.
+ *      SYNC_DIO_WAIT - The caller wants us to wait for all direct I/Os
+ *                     as well to ensure all data I/O completes before we
+ *                     return. Forms the drain side of the write barrier needed
+ *                     to safely quiesce the filesystem.
  *
  */
 /*ARGSUSED*/
@@ -883,10 +887,7 @@ xfs_sync(
 {
         xfs_mount_t     *mp = XFS_BHVTOM(bdp);
 
-        if (unlikely(flags == SYNC_QUIESCE))
-                return xfs_quiesce_fs(mp);
-        else
-                return xfs_syncsub(mp, flags, NULL);
+        return xfs_syncsub(mp, flags, NULL);
 }
 
 /*
@@ -1172,6 +1173,12 @@ xfs_sync_inodes(
                         }
 
                 }
+                /*
+                 * When freezing, we need to wait ensure direct I/O is complete
+                 * as well to ensure all data modification is complete here
+                 */
+                if (flags & SYNC_DIO_WAIT)
+                        vn_iowait(vp);
 
                 if (flags & SYNC_BDFLUSH) {
                         if ((flags & SYNC_ATTR) &&
@@ -1950,15 +1957,26 @@ xfs_showargs(
         return 0;
 }
 
+/*
+ * Second stage of a freeze. The data is already frozen, now we have to take
+ * care of the metadata. New transactions are already blocked, so we need to
+ * wait for any remaining transactions to drain out before proceding.
+ */
 STATIC void
 xfs_freeze(
         bhv_desc_t      *bdp)
 {
         xfs_mount_t     *mp = XFS_BHVTOM(bdp);
 
+        /* wait for all modifications to complete */
         while (atomic_read(&mp->m_active_trans) > 0)
                 delay(100);
 
+        /* flush inodes and push all remaining buffers out to disk */
+        xfs_quiesce_fs(mp);
+
+        BUG_ON(atomic_read(&mp->m_active_trans) > 0);
+
         /* Push the superblock and write an unmount record */
         xfs_log_unmount_write(mp);
         xfs_unmountfs_writesb(mp);