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BUG: KCSAN: data-race in blk_mq_rq_ctx_init / blk_mq_rq_ctx_init

write to 0xffff888101c81950 of 8 bytes by task 20365 on cpu 1:
 blk_mq_rq_ctx_init+0x3dc/0x4e0 block/blk-mq.c:344
 __blk_mq_alloc_request+0x270/0x290 block/blk-mq.c:399
 blk_mq_submit_bio+0x27f/0xec0 block/blk-mq.c:2199
 __submit_bio_noacct_mq block/blk-core.c:998 [inline]
 submit_bio_noacct+0x6e2/0x7d0 block/blk-core.c:1031
 submit_bio+0x10c/0x190
 submit_bio_wait+0x86/0xc0 block/bio.c:1248
 blkdev_issue_flush+0x7f/0xa0 block/blk-flush.c:458
 fat_file_fsync+0xe7/0x100 fs/fat/file.c:198
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2955 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3933
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 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

read to 0xffff888101c81950 of 8 bytes by task 20486 on cpu 0:
 blk_mq_rq_ctx_init+0x3ca/0x4e0 block/blk-mq.c:344
 __blk_mq_alloc_request+0x270/0x290 block/blk-mq.c:399
 blk_mq_submit_bio+0x27f/0xec0 block/blk-mq.c:2199
 __submit_bio_noacct_mq block/blk-core.c:998 [inline]
 submit_bio_noacct+0x6e2/0x7d0 block/blk-core.c:1031
 submit_bio+0x10c/0x190
 submit_bio_wait+0x86/0xc0 block/bio.c:1248
 blkdev_issue_flush+0x7f/0xa0 block/blk-flush.c:458
 fat_file_fsync+0xe7/0x100 fs/fat/file.c:198
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2955 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3933
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 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: 0x0000000000000b69 -> 0x0000000000000b6a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20486 Comm: syz-executor.2 Not tainted 5.15.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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