Commit 49dd742e authored by Bart Van Assche's avatar Bart Van Assche
Browse files

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



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: default avatarBart Van Assche <bvanassche@google.com>
parent 7f4abd95
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