[PATCH 1/3] xfs: flag all buffers as metadata

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

Now that REQ_META bios aren't treated specially in the CFQ I/O schedule
anymore, we can tag all buffers as metadata to make blktrace traces more
meaningful.  Note that we use buffers also to zero out partial blocks
in the preallocation / hole punching code, and while they operate on
data blocks the zeros written certainly aren't data.  I think this case
is borderline metadata enough to not bother special casing it.

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

Index: linux-2.6/fs/xfs/linux-2.6/xfs_buf.c
===================================================================
--- linux-2.6.orig/fs/xfs/linux-2.6/xfs_buf.c   2011-07-25 23:50:03.288230279 
+0200
+++ linux-2.6/fs/xfs/linux-2.6/xfs_buf.c        2011-07-25 23:50:22.208230167 
+0200
@@ -1224,6 +1224,9 @@ _xfs_buf_ioapply(
                rw = READ;
        }
 
+       /* we only use the buffer cache for meta-data */
+       rw |= REQ_META;
+
 next_chunk:
        atomic_inc(&bp->b_io_remaining);
        nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);