On Wed, May 24, 2017 at 01:40:13PM +0200, Jan Kara wrote:
> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
> synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
> definitions. generic_make_request_checks() however strips REQ_FUA and
> REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
> write cache and thus write effectively becomes asynchronous which can
> lead to performance regressions
>
> Fix the problem by making sure all bios which are synchronous are
> properly marked with REQ_SYNC.
Hi,
DM and MD are different trees, so probably you should separate them to 2
patches. For the md part (md.c, raid5-cache.c), some placed which use REQ_FUA
are missed, like raid5.c and raid5-ppl.c
Can't remember if others asked the question in your first post, sorry, but why
we don't add REQ_SYNC in generic_make_request_checks() if we are going to
stripe REQ_FUA, REQ_PREFLUSH. That will be less error prone.
Thanks,
Shaohua
> CC: [email protected]
> CC: Shaohua Li <[email protected]>
> CC: Mike Snitzer <[email protected]>
> CC: [email protected]
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> Signed-off-by: Jan Kara <[email protected]>
> ---
> drivers/md/dm-snap-persistent.c | 3 ++-
> drivers/md/md.c | 2 +-
> drivers/md/raid5-cache.c | 4 ++--
> 3 files changed, 5 insertions(+), 4 deletions(-)
>
> Guys, I don't know enough about DM/MD to judge whether I've identified all the
> places that want REQ_SYNC right. Can you please have a look?
>
> diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
> index b93476c3ba3f..b92ab4cb0710 100644
> --- a/drivers/md/dm-snap-persistent.c
> +++ b/drivers/md/dm-snap-persistent.c
> @@ -741,7 +741,8 @@ static void persistent_commit_exception(struct
> dm_exception_store *store,
> /*
> * Commit exceptions to disk.
> */
> - if (ps->valid && area_io(ps, REQ_OP_WRITE, REQ_PREFLUSH | REQ_FUA))
> + if (ps->valid && area_io(ps, REQ_OP_WRITE,
> + REQ_SYNC | REQ_PREFLUSH | REQ_FUA))
> ps->valid = 0;
>
> /*
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 10367ffe92e3..212a6777ff31 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -765,7 +765,7 @@ void md_super_write(struct mddev *mddev, struct md_rdev
> *rdev,
> test_bit(FailFast, &rdev->flags) &&
> !test_bit(LastDev, &rdev->flags))
> ff = MD_FAILFAST;
> - bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA | ff;
> + bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH | REQ_FUA | ff;
>
> atomic_inc(&mddev->pending_writes);
> submit_bio(bio);
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 4c00bc248287..0a7af8b0a80a 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -1782,7 +1782,7 @@ static int r5l_log_write_empty_meta_block(struct
> r5l_log *log, sector_t pos,
> mb->checksum = cpu_to_le32(crc32c_le(log->uuid_checksum,
> mb, PAGE_SIZE));
> if (!sync_page_io(log->rdev, pos, PAGE_SIZE, page, REQ_OP_WRITE,
> - REQ_FUA, false)) {
> + REQ_SYNC | REQ_FUA, false)) {
> __free_page(page);
> return -EIO;
> }
> @@ -2388,7 +2388,7 @@ r5c_recovery_rewrite_data_only_stripes(struct r5l_log
> *log,
> mb->checksum = cpu_to_le32(crc32c_le(log->uuid_checksum,
> mb, PAGE_SIZE));
> sync_page_io(log->rdev, ctx->pos, PAGE_SIZE, page,
> - REQ_OP_WRITE, REQ_FUA, false);
> + REQ_OP_WRITE, REQ_SYNC | REQ_FUA, false);
> sh->log_start = ctx->pos;
> list_add_tail(&sh->r5c, &log->stripe_in_journal_list);
> atomic_inc(&log->stripe_in_journal_count);
> --
> 2.12.0
>
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