syzbot

==================================================================
BUG: KCSAN: data-race in blk_mq_requeue_work / blk_mq_run_hw_queue

write to 0xffff8881026b3810 of 8 bytes by task 880 on cpu 1:
 __list_add include/linux/list.h:70 [inline]
 list_add_tail include/linux/list.h:100 [inline]
 blk_mq_request_bypass_insert block/blk-mq.c:1869 [inline]
 blk_mq_requeue_work+0x294/0x420 block/blk-mq.c:786
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 worker_thread+0x636/0xae0 kernel/workqueue.c:2421
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8881026b3810 of 8 bytes by task 560 on cpu 0:
 list_empty_careful include/linux/list.h:319 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:72 [inline]
 blk_mq_run_hw_queue+0x129/0x250 block/blk-mq.c:1614
 blk_mq_sched_insert_requests+0x13f/0x200 block/blk-mq-sched.c:491
 blk_mq_flush_plug_list+0x2f5/0x3c0 block/blk-mq.c:1942
 blk_flush_plug_list+0x235/0x260 block/blk-core.c:1749
 blk_mq_submit_bio+0x6c4/0xde0 block/blk-mq.c:2238
 __submit_bio_noacct_mq block/blk-core.c:1014 [inline]
 submit_bio_noacct+0x6f2/0x7e0 block/blk-core.c:1047
 submit_bio+0x16d/0x2b0 block/blk-core.c:1090
 iomap_dio_submit_bio fs/iomap/direct-io.c:76 [inline]
 iomap_dio_bio_actor+0x91d/0xb50 fs/iomap/direct-io.c:342
 iomap_dio_actor+0x26e/0x3b0 fs/iomap/direct-io.c:417
 iomap_apply+0x1e2/0x400 fs/iomap/apply.c:84
 __iomap_dio_rw+0x4c4/0xa10 fs/iomap/direct-io.c:553
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:641
 ext4_dio_write_iter fs/ext4/file.c:551 [inline]
 ext4_file_write_iter+0xa04/0x11d0 fs/ext4/file.c:661
 call_write_iter include/linux/fs.h:1977 [inline]
 aio_write+0x287/0x360 fs/aio.c:1581
 __io_submit_one fs/aio.c:1840 [inline]
 io_submit_one+0x82f/0x1350 fs/aio.c:1883
 __do_sys_io_submit fs/aio.c:1942 [inline]
 __se_sys_io_submit+0xf5/0x260 fs/aio.c:1912
 __x64_sys_io_submit+0x3f/0x50 fs/aio.c:1912
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 560 Comm: syz-executor.1 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
CPU: 0 PID: 560 Comm: syz-executor.1 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x137/0x19d lib/dump_stack.c:120
 fail_dump lib/fault-inject.c:52 [inline]
 should_fail+0x23c/0x250 lib/fault-inject.c:146
 __should_failslab+0x81/0x90 mm/failslab.c:33
 should_failslab+0x5/0x20 mm/slab_common.c:1273
 slab_pre_alloc_hook mm/slab.h:499 [inline]
 slab_alloc mm/slab.c:3306 [inline]
 kmem_cache_alloc+0x46/0x300 mm/slab.c:3502
 mempool_alloc_slab+0x16/0x20 mm/mempool.c:511
 mempool_alloc+0x8c/0x300 mm/mempool.c:391
 sg_pool_alloc+0x74/0x90 lib/sg_pool.c:67
 __sg_alloc_table+0xce/0x290 lib/scatterlist.c:302
 sg_alloc_table_chained+0xaf/0x140 lib/sg_pool.c:132
 scsi_alloc_sgtables+0x180/0x500 drivers/scsi/scsi_lib.c:1032
 sd_setup_read_write_cmnd drivers/scsi/sd.c:1229 [inline]
 sd_init_command+0x935/0x15f0 drivers/scsi/sd.c:1355
 scsi_prepare_cmd drivers/scsi/scsi_lib.c:1595 [inline]
 scsi_queue_rq+0x102d/0x14e0 drivers/scsi/scsi_lib.c:1673
 blk_mq_dispatch_rq_list+0x5b0/0xfa0 block/blk-mq.c:1369
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:186 [inline]
 blk_mq_do_dispatch_sched+0x370/0x610 block/blk-mq-sched.c:199
 __blk_mq_sched_dispatch_requests+0x21e/0x2c0 block/blk-mq-sched.c:310
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1488
 __blk_mq_delay_run_hw_queue+0x163/0x2d0 block/blk-mq.c:1565
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1618
 blk_mq_sched_insert_requests+0x13f/0x200 block/blk-mq-sched.c:491
 blk_mq_flush_plug_list+0x2f5/0x3c0 block/blk-mq.c:1942
 blk_flush_plug_list+0x235/0x260 block/blk-core.c:1749
 blk_mq_submit_bio+0x6c4/0xde0 block/blk-mq.c:2238
 __submit_bio_noacct_mq block/blk-core.c:1014 [inline]
 submit_bio_noacct+0x6f2/0x7e0 block/blk-core.c:1047
 submit_bio+0x16d/0x2b0 block/blk-core.c:1090
 iomap_dio_submit_bio fs/iomap/direct-io.c:76 [inline]
 iomap_dio_bio_actor+0x91d/0xb50 fs/iomap/direct-io.c:342
 iomap_dio_actor+0x26e/0x3b0 fs/iomap/direct-io.c:417
 iomap_apply+0x1e2/0x400 fs/iomap/apply.c:84
 __iomap_dio_rw+0x4c4/0xa10 fs/iomap/direct-io.c:553
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:641
 ext4_dio_write_iter fs/ext4/file.c:551 [inline]
 ext4_file_write_iter+0xa04/0x11d0 fs/ext4/file.c:661
 call_write_iter include/linux/fs.h:1977 [inline]
 aio_write+0x287/0x360 fs/aio.c:1581
 __io_submit_one fs/aio.c:1840 [inline]
 io_submit_one+0x82f/0x1350 fs/aio.c:1883
 __do_sys_io_submit fs/aio.c:1942 [inline]
 __se_sys_io_submit+0xf5/0x260 fs/aio.c:1912
 __x64_sys_io_submit+0x3f/0x50 fs/aio.c:1912
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8548815188 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 00000000004665f9
RDX: 0000000020000540 RSI: 0000000000000008 RDI: 00007f85487f2000
RBP: 00007f85488151d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffdc087bf1f R14: 00007f8548815300 R15: 0000000000022000