[PATCH 38/45] xfs: explicitly empty the AIL on unmount

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

Just like during a freeze we can make sure all metadata has been written back
on unmount by synchronously emptying the AIL.  Unlike during freeze we still
keep a synchronous inode reclaim pass to make sure we relclaim all clean
inodes as well.

After this the last caller of xfs_unmountfs_writesb is gone and it can be
removed.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>

---
 fs/xfs/xfs_mount.c |   56 +++++++++++------------------------------------------
 fs/xfs/xfs_mount.h |    1 
 2 files changed, 12 insertions(+), 45 deletions(-)

Index: xfs/fs/xfs/xfs_mount.c
===================================================================
--- xfs.orig/fs/xfs/xfs_mount.c 2011-10-27 22:40:10.132675928 +0200
+++ xfs/fs/xfs/xfs_mount.c      2011-10-27 22:40:13.126174145 +0200
@@ -22,6 +22,7 @@
 #include "xfs_log.h"
 #include "xfs_inum.h"
 #include "xfs_trans.h"
+#include "xfs_trans_priv.h"
 #include "xfs_sb.h"
 #include "xfs_ag.h"
 #include "xfs_dir2.h"
@@ -1544,15 +1545,15 @@ xfs_unmountfs(
        xfs_log_force(mp, XFS_LOG_SYNC);
 
        /*
-        * Do a delwri reclaim pass first so that as many dirty inodes are
-        * queued up for IO as possible. Then flush the buffers before making
-        * a synchronous path to catch all the remaining inodes are reclaimed.
-        * This makes the reclaim process as quick as possible by avoiding
-        * synchronous writeout and blocking on inodes already in the delwri
-        * state as much as possible.
+        * Flush all pending changes from the AIL.
+        */
+       xfs_ail_push_all_sync(mp->m_ail);
+
+       /*
+        * And reclaim all inodes.  At this point there should be no dirty
+        * inode, and none should be pinned or locked, but use synchronous
+        * reclaim just to be sure.
         */
-       xfs_reclaim_inodes(mp, 0);
-       xfs_flush_buftarg(mp->m_ddev_targp, 1);
        xfs_reclaim_inodes(mp, SYNC_WAIT);
 
        xfs_qm_unmount(mp);
@@ -1588,15 +1589,12 @@ xfs_unmountfs(
        if (error)
                xfs_warn(mp, "Unable to update superblock counters. "
                                "Freespace may not be correct on next mount.");
-       xfs_unmountfs_writesb(mp);
 
        /*
-        * Make sure all buffers have been flushed and completed before
-        * unmounting the log.
+        * At this point we might have modified the superblock again and thus
+        * added an item to the AIL, thus flush it again.
         */
-       error = xfs_flush_buftarg(mp->m_ddev_targp, 1);
-       if (error)
-               xfs_warn(mp, "%d busy buffers during unmount.", error);
+       xfs_ail_push_all_sync(mp->m_ail);
        xfs_wait_buftarg(mp->m_ddev_targp);
 
        xfs_log_unmount_write(mp);
@@ -1657,36 +1655,6 @@ xfs_log_sbcount(xfs_mount_t *mp)
        return error;
 }
 
-int
-xfs_unmountfs_writesb(xfs_mount_t *mp)
-{
-       xfs_buf_t       *sbp;
-       int             error = 0;
-
-       /*
-        * skip superblock write if fs is read-only, or
-        * if we are doing a forced umount.
-        */
-       if (!((mp->m_flags & XFS_MOUNT_RDONLY) ||
-               XFS_FORCED_SHUTDOWN(mp))) {
-
-               sbp = xfs_getsb(mp, 0);
-
-               XFS_BUF_UNDONE(sbp);
-               XFS_BUF_UNREAD(sbp);
-               xfs_buf_delwri_dequeue(sbp);
-               XFS_BUF_WRITE(sbp);
-               XFS_BUF_UNASYNC(sbp);
-               ASSERT(sbp->b_target == mp->m_ddev_targp);
-               xfsbdstrat(mp, sbp);
-               error = xfs_buf_iowait(sbp);
-               if (error)
-                       xfs_buf_ioerror_alert(sbp, __func__);
-               xfs_buf_relse(sbp);
-       }
-       return error;
-}
-
 /*
  * xfs_mod_sb() can be used to copy arbitrary changes to the
  * in-core superblock into the superblock buffer to be logged.
Index: xfs/fs/xfs/xfs_mount.h
===================================================================
--- xfs.orig/fs/xfs/xfs_mount.h 2011-10-27 22:39:57.502188861 +0200
+++ xfs/fs/xfs/xfs_mount.h      2011-10-27 22:40:13.130172675 +0200
@@ -379,7 +379,6 @@ extern __uint64_t xfs_default_resblks(xf
 extern int     xfs_mountfs(xfs_mount_t *mp);
 
 extern void    xfs_unmountfs(xfs_mount_t *);
-extern int     xfs_unmountfs_writesb(xfs_mount_t *);
 extern int     xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
 extern int     xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
                        uint, int);