BUG: KCSAN: data-race in blk_mq_rq_ctx_init / blk_mq_rq_ctx_init

write to 0xffff88810172cd50 of 8 bytes by task 11150 on cpu 0:
 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
 ext4_io_submit+0xcd/0xf0 fs/ext4/page-io.c:379
 ext4_writepages+0xb2a/0x1d70 fs/ext4/inode.c:2818
 do_writepages+0x26b/0x3c0 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:400 [inline]
 __filemap_fdatawrite_range mm/filemap.c:433 [inline]
 __filemap_fdatawrite mm/filemap.c:439 [inline]
 filemap_flush+0x154/0x180 mm/filemap.c:466
 ext4_alloc_da_blocks+0x47/0xd0 fs/ext4/inode.c:3106
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810172cd50 of 8 bytes by task 11154 on cpu 1:
 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
 ext4_io_submit+0xcd/0xf0 fs/ext4/page-io.c:379
 ext4_writepages+0xb2a/0x1d70 fs/ext4/inode.c:2818
 do_writepages+0x26b/0x3c0 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:400 [inline]
 __filemap_fdatawrite_range mm/filemap.c:433 [inline]
 __filemap_fdatawrite mm/filemap.c:439 [inline]
 filemap_flush+0x154/0x180 mm/filemap.c:466
 ext4_alloc_da_blocks+0x47/0xd0 fs/ext4/inode.c:3106
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000008b01 -> 0x0000000000008b02

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 11154 Comm: syz-executor.4 Not tainted 5.15.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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