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BUG: KCSAN: data-race in blk_mq_rq_ctx_init / blk_mq_rq_ctx_init

read to 0xffff88810273b950 of 8 bytes by task 3757 on cpu 0:
 blk_mq_rq_ctx_init+0x3ca/0x4e0 block/blk-mq.c:351
 __blk_mq_alloc_request+0x270/0x290 block/blk-mq.c:406
 blk_mq_submit_bio+0x27f/0xec0 block/blk-mq.c:2206
 __submit_bio+0x41a/0x480 block/blk-core.c:929
 __submit_bio_noacct_mq block/blk-core.c:1009 [inline]
 submit_bio_noacct+0x46d/0x530 block/blk-core.c:1039
 submit_bio+0x10c/0x190
 iomap_dio_submit_bio fs/iomap/direct-io.c:74 [inline]
 iomap_dio_bio_iter+0x990/0xbc0 fs/iomap/direct-io.c:342
 __iomap_dio_rw+0x8d8/0x1010 fs/iomap/direct-io.c:569
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:649
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x21a/0x290 fs/ext4/file.c:128
 call_read_iter include/linux/fs.h:2157 [inline]
 generic_file_splice_read+0x24f/0x330 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff88810273b950 of 8 bytes by task 3771 on cpu 1:
 blk_mq_rq_ctx_init+0x3dc/0x4e0 block/blk-mq.c:351
 __blk_mq_alloc_request+0x270/0x290 block/blk-mq.c:406
 blk_mq_submit_bio+0x27f/0xec0 block/blk-mq.c:2206
 __submit_bio+0x41a/0x480 block/blk-core.c:929
 __submit_bio_noacct_mq block/blk-core.c:1009 [inline]
 submit_bio_noacct+0x46d/0x530 block/blk-core.c:1039
 submit_bio+0x10c/0x190
 iomap_dio_submit_bio fs/iomap/direct-io.c:74 [inline]
 iomap_dio_bio_iter+0x990/0xbc0 fs/iomap/direct-io.c:342
 __iomap_dio_rw+0x8d8/0x1010 fs/iomap/direct-io.c:569
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:649
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x21a/0x290 fs/ext4/file.c:128
 call_read_iter include/linux/fs.h:2157 [inline]
 generic_file_splice_read+0x24f/0x330 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x63e/0xbb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000000018ed -> 0x00000000000018ee

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3771 Comm: syz-executor.2 Not tainted 5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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