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authorNeilBrown <neilb@suse.com>2019-03-29 20:46:16 +0300
committerJens Axboe <axboe@kernel.dk>2019-04-01 21:11:48 +0300
commit4bc034d35377196c854236133b07730a777c4aba (patch)
tree58b75009263777beb5fdf4a058af5f6ba2a3d1be /drivers/md/md.h
parent4f4fd7c5798bbdd5a03a60f6269cf1177fbd11ef (diff)
downloadlinux-4bc034d35377196c854236133b07730a777c4aba.tar.xz
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.h22
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;