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ANDROID: block: Fix a deadlock related freezing zoned storage devices

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blk_mq_freeze_queue() never terminates if one or more bios are on the plug
list and if the block device driver defines a .submit_bio() method.
This is the case for device mapper drivers. The deadlock happens because
blk_mq_freeze_queue() waits for q_usage_counter to drop to zero, because
a queue reference is held by bios on the plug list and because the
__bio_queue_enter() call in __submit_bio() waits for the queue to be
unfrozen.

This patch fixes the following deadlock:

Workqueue: dm-51_zwplugs blk_zone_wplug_bio_work
Call trace:
 __schedule+0xb08/0x1160
 schedule+0x48/0xc8
 __bio_queue_enter+0xcc/0x1d0
 __submit_bio+0x100/0x1b0
 submit_bio_noacct_nocheck+0x230/0x49c
 blk_zone_wplug_bio_work+0x168/0x250
 process_one_work+0x26c/0x65c
 worker_thread+0x33c/0x498
 kthread+0x110/0x134
 ret_from_fork+0x10/0x20

Call trace:
 __switch_to+0x230/0x410
 __schedule+0xb08/0x1160
 schedule+0x48/0xc8
 blk_mq_freeze_queue_wait+0x78/0xb8
 blk_mq_freeze_queue+0x90/0xa4
 queue_attr_store+0x7c/0xf0
 sysfs_kf_write+0x98/0xc8
 kernfs_fop_write_iter+0x12c/0x1d4
 vfs_write+0x340/0x3ac
 ksys_write+0x78/0xe8

Bug: 415836627
Change-Id: I56e9007b4836f3b89a5c879873e9a994e0f5f7a7
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2025-05-14 11:23:56 -07:00
parent 7f4abd95ae
commit 49dd742eed
1 changed files with 16 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
block/blk-core.c
View File

@@ -621,6 +621,13 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
return BLK_STS_OK;
}
/*
* Do not call bio_queue_enter() if the BIO_ZONE_WRITE_PLUGGING flag has been
* set because this causes blk_mq_freeze_queue() to deadlock if
* blk_zone_wplug_bio_work() submits a bio. Calling bio_queue_enter() for bios
* on the plug list is not necessary since a q_usage_counter reference is held
* while a bio is on the plug list.
*/
static void __submit_bio(struct bio *bio)
{
/* If plug is not used, add new plug here to cache nsecs time. */
@@ -633,8 +640,12 @@ static void __submit_bio(struct bio *bio)
if (!bdev_test_flag(bio->bi_bdev, BD_HAS_SUBMIT_BIO)) {
blk_mq_submit_bio(bio);
} else if (likely(bio_queue_enter(bio) == 0)) {
} else {
struct gendisk *disk = bio->bi_bdev->bd_disk;
bool zwp = bio_zone_write_plugging(bio);
if (unlikely(!zwp && bio_queue_enter(bio) != 0))
goto finish_plug;
if ((bio->bi_opf & REQ_POLLED) &&
!(disk->queue->limits.features & BLK_FEAT_POLL)) {
@@ -643,9 +654,12 @@ static void __submit_bio(struct bio *bio)
} else {
disk->fops->submit_bio(bio);
}
blk_queue_exit(disk->queue);
if (!zwp)
blk_queue_exit(disk->queue);
}
finish_plug:
blk_finish_plug(&plug);
}