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BUG: KCSAN: data-race in blk_mq_rq_ctx_init / blk_mq_rq_ctx_init

read-write to 0xffff888102e39548 of 8 bytes by task 18745 on cpu 1:
 blk_mq_rq_ctx_init+0x3f0/0x4f0 block/blk-mq.c:344
 __blk_mq_alloc_request+0x295/0x2b0 block/blk-mq.c:398
 blk_mq_submit_bio+0x26c/0x1000 block/blk-mq.c:2163
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x75d/0x910 block/blk-core.c:1061
 submit_bio+0x1f3/0x350 block/blk-core.c:1131
 iomap_dio_submit_bio fs/iomap/direct-io.c:76 [inline]
 iomap_dio_bio_actor+0x83d/0xa60 fs/iomap/direct-io.c:312
 iomap_dio_actor+0x266/0x3a0 fs/iomap/direct-io.c:387
 iomap_apply+0x1e1/0x4a0 fs/iomap/apply.c:84
 __iomap_dio_rw+0x448/0x9b0 fs/iomap/direct-io.c:517
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:605
 ext4_dio_write_iter fs/ext4/file.c:552 [inline]
 ext4_file_write_iter+0xe06/0x1090 fs/ext4/file.c:662
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read-write to 0xffff888102e39548 of 8 bytes by task 18752 on cpu 0:
 blk_mq_rq_ctx_init+0x3f0/0x4f0 block/blk-mq.c:344
 __blk_mq_alloc_request+0x295/0x2b0 block/blk-mq.c:398
 blk_mq_submit_bio+0x26c/0x1000 block/blk-mq.c:2163
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x75d/0x910 block/blk-core.c:1061
 submit_bio+0x1f3/0x350 block/blk-core.c:1131
 ext4_io_submit+0xcd/0xf0 fs/ext4/page-io.c:379
 ext4_writepages+0x144a/0x1e50 fs/ext4/inode.c:2821
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2737 [inline]
 ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6d4/0x7c0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18752 Comm: syz-executor.0 Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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