gfs2: add flag REQ_PRIO for metadata I/O (e477b24b) · Commits · 戴 / test

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:

Coly Li <colyli@suse.de> Signed-off-by:

Bob Peterson <rpeterso@redhat.com>

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;

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