diff options
author | 2019-03-29 10:46:16 -0700 | |
---|---|---|
committer | 2019-04-01 12:11:48 -0600 | |
commit | 4bc034d35377196c854236133b07730a777c4aba (patch) | |
tree | 58b75009263777beb5fdf4a058af5f6ba2a3d1be /drivers/md/md.h | |
parent | Don't jump to compute_result state from check_result state (diff) | |
download | linux-4bc034d35377196c854236133b07730a777c4aba.tar.gz linux-4bc034d35377196c854236133b07730a777c4aba.tar.bz2 linux-4bc034d35377196c854236133b07730a777c4aba.zip |
Revert "MD: fix lock contention for flush bios"
This reverts commit 5a409b4f56d50b212334f338cb8465d65550cd85.
This patch has two problems.
1/ it make multiple calls to submit_bio() from inside a make_request_fn.
The bios thus submitted will be queued on current->bio_list and not
submitted immediately. As the bios are allocated from a mempool,
this can theoretically result in a deadlock - all the pool of requests
could be in various ->bio_list queues and a subsequent mempool_alloc
could block waiting for one of them to be released.
2/ It aims to handle a case when there are many concurrent flush requests.
It handles this by submitting many requests in parallel - all of which
are identical and so most of which do nothing useful.
It would be more efficient to just send one lower-level request, but
allow that to satisfy multiple upper-level requests.
Fixes: 5a409b4f56d5 ("MD: fix lock contention for flush bios")
Cc: <stable@vger.kernel.org> # v4.19+
Tested-by: Xiao Ni <xni@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md/md.h')
-rw-r--r-- | drivers/md/md.h | 22 |
1 files changed, 7 insertions, 15 deletions
diff --git a/drivers/md/md.h b/drivers/md/md.h index c52afb52c776..2deb84fa93f9 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -252,19 +252,6 @@ enum mddev_sb_flags { MD_SB_NEED_REWRITE, /* metadata write needs to be repeated */ }; -#define NR_FLUSH_INFOS 8 -#define NR_FLUSH_BIOS 64 -struct flush_info { - struct bio *bio; - struct mddev *mddev; - struct work_struct flush_work; - atomic_t flush_pending; -}; -struct flush_bio { - struct flush_info *fi; - struct md_rdev *rdev; -}; - struct mddev { void *private; struct md_personality *pers; @@ -470,8 +457,13 @@ struct mddev { * metadata and bitmap writes */ - mempool_t *flush_pool; - mempool_t *flush_bio_pool; + /* Generic flush handling. + * The last to finish preflush schedules a worker to submit + * the rest of the request (without the REQ_PREFLUSH flag). + */ + struct bio *flush_bio; + atomic_t flush_pending; + struct work_struct flush_work; struct work_struct event_work; /* used by dm to report failure event */ void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev); struct md_cluster_info *cluster_info; |