From: Coly Li <[email protected]> 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 <[email protected]> Signed-off-by: Bob Peterson <[email protected]> --- fs/gfs2/bmap.c | 5 +++-- fs/gfs2/dir.c | 4 +++- fs/gfs2/meta_io.c | 6 ++++-- fs/gfs2/quota.c | 2 +- 4 files changed, 11 insertions(+), 6 deletions(-) diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c index 9fa3aef9a5b3..fa3ea29f39cf 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -291,8 +291,9 @@ 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, - rabh); + submit_bh(REQ_OP_READ, + REQ_RAHEAD | REQ_META | REQ_PRIO, + rabh); continue; } unlock_buffer(rabh); diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c index db427658ccd9..0741e4018f8c 100644 --- a/fs/gfs2/dir.c +++ b/fs/gfs2/dir.c @@ -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); diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c index 4da7745c890a..61ef6c9be816 100644 --- a/fs/gfs2/meta_io.c +++ b/fs/gfs2/meta_io.c @@ -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--; diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c index c2ca9566b764..739adf105d7f 100644 --- a/fs/gfs2/quota.c +++ b/fs/gfs2/quota.c @@ -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; -- 2.13.5
