diff options
| author | Coly Li | 2019-02-09 12:53:11 +0800 |
|---|---|---|
| committer | Jens Axboe | 2019-02-09 07:18:33 -0700 |
| commit | dc7292a5bcb4c878b076fca2ac3fc22f81b8f8df (patch) | |
| tree | cf12759359099616e3604c2c8137d3686ea1310a | |
| parent | a91fbda49f746119828f7e8ad0f0aa2ab0578f65 (diff) | |
bcache: use (REQ_META|REQ_PRIO) to indicate bio for metadata
In 'commit 752f66a75aba ("bcache: use REQ_PRIO to indicate bio for
metadata")' REQ_META is replaced by REQ_PRIO to indicate metadata bio.
This assumption is not always correct, e.g. XFS uses REQ_META to mark
metadata bio other than REQ_PRIO. This is why Nix noticed that bcache
does not cache metadata for XFS after the above commit.
Thanks to Dave Chinner, he explains the difference between REQ_META and
REQ_PRIO from view of file system developer. Here I quote part of his
explanation from mailing list,
REQ_META is used for metadata. REQ_PRIO is used to communicate to
the lower layers that the submitter considers this IO to be more
important that non REQ_PRIO IO and so dispatch should be expedited.
IOWs, if the filesystem considers metadata IO to be more important
that user data IO, then it will use REQ_PRIO | REQ_META rather than
just REQ_META.
Then it seems bios with REQ_META or REQ_PRIO should both be cached for
performance optimation, because they are all probably low I/O latency
demand by upper layer (e.g. file system).
So in this patch, when we want to decide whether to bypass the cache,
REQ_META and REQ_PRIO are both checked. Then both metadata and
high priority I/O requests will be handled properly.
Reported-by: Nix <nix@esperi.org.uk>
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Andre Noll <maan@tuebingen.mpg.de>
Tested-by: Nix <nix@esperi.org.uk>
Cc: stable@vger.kernel.org
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/md/bcache/request.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index 15070412a32e..f101bfe8657a 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -392,10 +392,11 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio) /* * Flag for bypass if the IO is for read-ahead or background, - * unless the read-ahead request is for metadata (eg, for gfs2). + * unless the read-ahead request is for metadata + * (eg, for gfs2 or xfs). */ if (bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND) && - !(bio->bi_opf & REQ_PRIO)) + !(bio->bi_opf & (REQ_META|REQ_PRIO))) goto skip; if (bio->bi_iter.bi_sector & (c->sb.block_size - 1) || @@ -877,7 +878,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s, } if (!(bio->bi_opf & REQ_RAHEAD) && - !(bio->bi_opf & REQ_PRIO) && + !(bio->bi_opf & (REQ_META|REQ_PRIO)) && s->iop.c->gc_stats.in_use < CUTOFF_CACHE_READA) reada = min_t(sector_t, dc->readahead >> 9, get_capacity(bio->bi_disk) - bio_end_sector(bio)); |