[GFS2] Reduce truncate IO traffic

Current GFS2 setattr call unconditionally invokes do_shrink even the
requested size and actual file size are equal. This has generated large
amount of extra IOs found during NFS benchmark runs. This patch moves
the relevant logic out of shrink code path. Since setattr is a system
call, the time stamps update is still required.

Signed-off-by: S. Wendy Cheng <wcheng@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index cd805a66880ddd3f24459be574bd868d29f2d801..9b8990444e6cf9e6ec737fe2738ac4fde639ae39 100644 (file)
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1085,6 +1085,33 @@ static int do_shrink(struct gfs2_inode *ip, u64 size)
        return error;
 }
 
+static int do_touch(struct gfs2_inode *ip, u64 size)
+{
+       struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+       struct buffer_head *dibh;
+       int error;
+
+       error = gfs2_trans_begin(sdp, RES_DINODE, 0);
+       if (error)
+               return error;
+
+       down_write(&ip->i_rw_mutex);
+
+       error = gfs2_meta_inode_buffer(ip, &dibh);
+       if (error)
+               goto do_touch_out;
+
+       ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
+       gfs2_trans_add_bh(ip->i_gl, dibh, 1);
+       gfs2_dinode_out(ip, dibh->b_data);
+       brelse(dibh);
+
+do_touch_out:
+       up_write(&ip->i_rw_mutex);
+       gfs2_trans_end(sdp);
+       return error;
+}
+
 /**
  * gfs2_truncatei - make a file a given size
  * @ip: the inode
@@ -1105,8 +1132,11 @@ int gfs2_truncatei(struct gfs2_inode *ip, u64 size)
 
        if (size > ip->i_di.di_size)
                error = do_grow(ip, size);
-       else
+       else if (size < ip->i_di.di_size)
                error = do_shrink(ip, size);
+       else
+               /* update time stamps */
+               error = do_touch(ip, size);
 
        return error;
 }