From e477b24b507998bc6568316a2e034025960d2404 Mon Sep 17 00:00:00 2001 From: Coly Li Date: Fri, 21 Jul 2017 07:48:22 -0500 Subject: 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: Coly Li Signed-off-by: Bob Peterson --- fs/gfs2/dir.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'fs/gfs2/dir.c') 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); -- cgit v1.2.3