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Commit e477b24b authored by Coly Li's avatar Coly Li Committed by Bob Peterson
Browse files

gfs2: add flag REQ_PRIO for metadata I/O 



When gfs2 does metadata I/O, only REQ_META is used as a metadata hint of
the bio. But flag REQ_META is just a hint for block trace, not for block
layer code to handle a bio as metadata request.

For some of metadata I/Os of gfs2, A REQ_PRIO flag on the metadata bio
would be very informative to block layer code. For example, if bcache is
used as a I/O cache for gfs2, it will be possible for bcache code to get
the hint and cache the pre-fetched metadata blocks on cache device. This
behavior may be helpful to improve metadata I/O performance if the
following requests hit the cache.

Here are the locations in gfs2 code where a REQ_PRIO flag should be added,
- All places where REQ_READAHEAD is used, gfs2 code uses this flag for
  metadata read ahead.
- In gfs2_meta_rq() where the first metadata block is read in.
- In gfs2_write_buf_to_page(), read in quota metadata blocks to have them
  up to date.
These metadata blocks are probably to be accessed again in future, adding
a REQ_PRIO flag may have bcache to keep such metadata in fast cache
device. For system without a cache layer, REQ_PRIO can still provide hint
to block layer to handle metadata requests more properly.

Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
parent e7cb550d

fs/gfs2/bmap.c

+3 −2
Original line number Diff line number Diff line
@@ -291,7 +291,8 @@ static void gfs2_metapath_ra(struct gfs2_glock *gl, 
		if (trylock_buffer(rabh)) {

			if (!buffer_uptodate(rabh)) {

				rabh->b_end_io = end_buffer_read_sync;

				submit_bh(REQ_OP_READ, REQ_RAHEAD | REQ_META,

				submit_bh(REQ_OP_READ,

					  REQ_RAHEAD | REQ_META | REQ_PRIO,

					  rabh);

				continue;

			}

fs/gfs2/dir.c

+3 −1
Original line number Diff line number Diff line
@@ -1514,7 +1514,9 @@ static void gfs2_dir_readahead(struct inode *inode, unsigned hsize, u32 index, 
				continue;

			}

			bh->b_end_io = end_buffer_read_sync;

			submit_bh(REQ_OP_READ, REQ_RAHEAD | REQ_META, bh);

			submit_bh(REQ_OP_READ,

				  REQ_RAHEAD | REQ_META | REQ_PRIO,

				  bh);

			continue;

		}

		brelse(bh);

fs/gfs2/meta_io.c

+4 −2
Original line number Diff line number Diff line
@@ -453,7 +453,7 @@ struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen) 
	if (buffer_uptodate(first_bh))

		goto out;

	if (!buffer_locked(first_bh))

		ll_rw_block(REQ_OP_READ, REQ_META, 1, &first_bh);

		ll_rw_block(REQ_OP_READ, REQ_META | REQ_PRIO, 1, &first_bh);



	dblock++;

	extlen--;
@@ -462,7 +462,9 @@ struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen) 
		bh = gfs2_getbuf(gl, dblock, CREATE);



		if (!buffer_uptodate(bh) && !buffer_locked(bh))

			ll_rw_block(REQ_OP_READ, REQ_RAHEAD | REQ_META, 1, &bh);

			ll_rw_block(REQ_OP_READ,

				    REQ_RAHEAD | REQ_META | REQ_PRIO,

				    1, &bh);

		brelse(bh);

		dblock++;

		extlen--;

fs/gfs2/quota.c

+1 −1
Original line number Diff line number Diff line
@@ -730,7 +730,7 @@ static int gfs2_write_buf_to_page(struct gfs2_inode *ip, unsigned long index, 
		if (PageUptodate(page))

			set_buffer_uptodate(bh);

		if (!buffer_uptodate(bh)) {

			ll_rw_block(REQ_OP_READ, REQ_META, 1, &bh);

			ll_rw_block(REQ_OP_READ, REQ_META | REQ_PRIO, 1, &bh);

			wait_on_buffer(bh);

			if (!buffer_uptodate(bh))

				goto unlock_out;