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block: fix lost bio for plug enabled bio based device

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With the following two conditions, bio will be lost:

1) blk plug is not enabled, for example, __blkdev_direct_IO_simple() and
__blkdev_direct_IO_async();
2) bio plug is enabled, for example write IO for raid1/raid10 while
bitmap is enabled;

Root cause is that blk_finish_plug() will add the bio to
curent->bio_list, while such bio will not be handled:

__submit_bio_noacct
 current->bio_list = bio_list_on_stack;
 blk_start_plug

 do {
  dm_submit_bio
   md_handle_request
    raid10_write_request
     -> generate new bio for underlying disks
     raid1_add_bio_to_plug -> bio is added to plug
 } while ((bio = bio_list_pop(&bio_list_on_stack[0])))
 -> previous bio are all handled

 blk_finish_plug
  raid10_unplug
   raid1_submit_write
    submit_bio_noacct
     if (current->bio_list)
      bio_list_add(&current->bio_list[0], bio)
      -> add new bio

 current->bio_list = NULL
 -> new bio is lost

Fix the problem by moving the plug into the while loop, so that
current->bio_list will still be handled after blk_finish_plug().

By the way, enable plug for raid1/raid10 in this case will also prevent
delay IO handling into daemon thread, which should also improve IO
performance.

Fixes: 060406c61c ("block: add plug while submitting IO")
Reported-by: Changhui Zhong <czhong@redhat.com>
Closes: https://lore.kernel.org/all/CAGVVp+Xsmzy2G9YuEatfMT6qv1M--YdOCQ0g7z7OVmcTbBxQAg@mail.gmail.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Tested-by: Changhui Zhong <czhong@redhat.com>
Link: https://lore.kernel.org/r/20240521200308.983986-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yu Kuai 2024-05-22 04:03:08 +08:00 committed by Jens Axboe
parent f0eab3e8d1
commit 9a42891c35
1 changed files with 7 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
block/blk-core.c
View File

@ -613,9 +613,14 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
static void __submit_bio(struct bio *bio)
{
/* If plug is not used, add new plug here to cache nsecs time. */
struct blk_plug plug;
if (unlikely(!blk_crypto_bio_prep(&bio)))
return;
blk_start_plug(&plug);
if (!bio->bi_bdev->bd_has_submit_bio) {
blk_mq_submit_bio(bio);
} else if (likely(bio_queue_enter(bio) == 0)) {
@ -624,6 +629,8 @@ static void __submit_bio(struct bio *bio)
disk->fops->submit_bio(bio);
blk_queue_exit(disk->queue);
}
blk_finish_plug(&plug);
}
/*
@ -648,13 +655,11 @@ static void __submit_bio(struct bio *bio)
static void __submit_bio_noacct(struct bio *bio)
{
struct bio_list bio_list_on_stack[2];
struct blk_plug plug;
BUG_ON(bio->bi_next);
bio_list_init(&bio_list_on_stack[0]);
current->bio_list = bio_list_on_stack;
blk_start_plug(&plug);
do {
struct request_queue *q = bdev_get_queue(bio->bi_bdev);
@ -688,23 +693,19 @@ static void __submit_bio_noacct(struct bio *bio)
bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
} while ((bio = bio_list_pop(&bio_list_on_stack[0])));
blk_finish_plug(&plug);
current->bio_list = NULL;
}
static void __submit_bio_noacct_mq(struct bio *bio)
{
struct bio_list bio_list[2] = { };
struct blk_plug plug;
current->bio_list = bio_list;
blk_start_plug(&plug);
do {
__submit_bio(bio);
} while ((bio = bio_list_pop(&bio_list[0])));
blk_finish_plug(&plug);
current->bio_list = NULL;
}