[moderation] [block?] KCSAN: data-race in __dd_dispatch_request / ll_back_merge_fn (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 69b54314c975 Merge tag 'kbuild-fixes-v6.14' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13af7df8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e757e3762bd630b
dashboard link: https://syzkaller.appspot.com/bug?extid=500bf7a08a7f7e1486bb
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2b7567096e2a/disk-69b54314.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2676ba455ec2/vmlinux-69b54314.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f886f31e555f/bzImage-69b54314.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+500bf7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __dd_dispatch_request / ll_back_merge_fn

write to 0xffff888100e52838 of 8 bytes by task 322 on cpu 0:
deadline_remove_request block/mq-deadline.c:186 [inline]
deadline_move_request block/mq-deadline.c:248 [inline]
__dd_dispatch_request+0x603/0x6e0 block/mq-deadline.c:416
dd_dispatch_request+0x1d4/0x2c0 block/mq-deadline.c:479
__blk_mq_do_dispatch_sched block/blk-mq-sched.c:118 [inline]
blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
__blk_mq_sched_dispatch_requests+0x3f7/0xd50 block/blk-mq-sched.c:309
blk_mq_sched_dispatch_requests+0x88/0x120 block/blk-mq-sched.c:331
blk_mq_run_work_fn+0x65/0xe0 block/blk-mq.c:2530
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
kthread+0x4ae/0x520 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff888100e52838 of 8 bytes by task 76 on cpu 1:
req_set_nomerge block/blk.h:421 [inline]
ll_back_merge_fn+0x307/0x4f0 block/blk-merge.c:648
bio_attempt_back_merge+0x5c/0x500 block/blk-merge.c:986
blk_attempt_bio_merge+0x470/0x4c0 block/blk-merge.c:1083
blk_attempt_plug_merge+0xb5/0x100 block/blk-merge.c:1129
blk_mq_attempt_bio_merge block/blk-mq.c:2958 [inline]
blk_mq_submit_bio+0x715/0xf30 block/blk-mq.c:3118
__submit_bio+0xf2/0x4f0 block/blk-core.c:628
__submit_bio_noacct_mq block/blk-core.c:715 [inline]
submit_bio_noacct_nocheck+0x295/0x6e0 block/blk-core.c:744
submit_bio_noacct+0x6e1/0x930 block/blk-core.c:867
submit_bio+0x218/0x230 block/blk-core.c:909
swap_writepage_bdev_async mm/page_io.c:450 [inline]
__swap_writepage+0x876/0xe20 mm/page_io.c:473
swap_writepage+0x39d/0x7a0 mm/page_io.c:288
shmem_writepage+0x940/0xa60 mm/shmem.c:1647
pageout mm/vmscan.c:696 [inline]
shrink_folio_list+0x1dc8/0x2640 mm/vmscan.c:1402
evict_folios+0x2511/0x2fc0 mm/vmscan.c:4660
try_to_shrink_lruvec+0x3f7/0x580 mm/vmscan.c:4821
shrink_one+0x176/0x4b0 mm/vmscan.c:4866
shrink_many mm/vmscan.c:4929 [inline]
lru_gen_shrink_node mm/vmscan.c:5007 [inline]
shrink_node+0x1890/0x1d80 mm/vmscan.c:5978
kswapd_shrink_node mm/vmscan.c:6807 [inline]
balance_pgdat mm/vmscan.c:6999 [inline]
kswapd+0xf5b/0x1a70 mm/vmscan.c:7264
kthread+0x4ae/0x520 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0xffff888102e83a80 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 76 Comm: kswapd0 Not tainted 6.14.0-rc1-syzkaller-00276-g69b54314c975 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.