xfs: force buffer writeback before blocking on the ilock in inode reclaim

If we are doing synchronous inode reclaim we block the VM from making
progress in memory reclaim.  So if we encouter a flush locked inode
promote it in the delwri list and wake up xfsbufd to write it out now.
Without this we can get hangs of up to 30 seconds during workloads hitting
synchronous inode reclaim.

The scheme is copied from what we do for dquot reclaims.

Reported-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c0237c602f11..755ee8164880 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2835,6 +2835,27 @@ corrupt_out:
         return XFS_ERROR(EFSCORRUPTED);
 }
 
+void
+xfs_promote_inode(
+        struct xfs_inode        *ip)
+{
+        struct xfs_buf          *bp;
+
+        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
+
+        bp = xfs_incore(ip->i_mount->m_ddev_targp, ip->i_imap.im_blkno,
+                        ip->i_imap.im_len, XBF_TRYLOCK);
+        if (!bp)
+                return;
+
+        if (XFS_BUF_ISDELAYWRITE(bp)) {
+                xfs_buf_delwri_promote(bp);
+                wake_up_process(ip->i_mount->m_ddev_targp->bt_task);
+        }
+
+        xfs_buf_relse(bp);
+}
+
 /*
  * Return a pointer to the extent record at file index idx.
  */