[moderation] [fs?] [mm?] KCSAN: data-race in fprop_reflect_period_percpu / fprop_reflect_period_percpu (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2661062f16b Linux 6.10-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15bbc02a980000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e87b541dc1fc960
dashboard link: https://syzkaller.appspot.com/bug?extid=7139e8dee7b64af430c7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linux-...@vger.kernel.org linu...@kvack.org wi...@infradead.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/95983fc4e96c/disk-f2661062.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4c822f21955c/vmlinux-f2661062.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0406d0880c80/bzImage-f2661062.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7139e8...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fprop_reflect_period_percpu / fprop_reflect_period_percpu

write to 0xffff8881088a61c8 of 4 bytes by task 27496 on cpu 0:
fprop_reflect_period_percpu+0x170/0x1a0 lib/flex_proportions.c:134
fprop_fraction_percpu+0x98/0x150 lib/flex_proportions.c:156
__wb_calc_thresh mm/page-writeback.c:875 [inline]
wb_over_bg_thresh+0x203/0x760 mm/page-writeback.c:2120
wb_check_background_flush fs/fs-writeback.c:2189 [inline]
wb_do_writeback fs/fs-writeback.c:2287 [inline]
wb_workfn+0x643/0x940 fs/fs-writeback.c:2314
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
worker_thread+0x526/0x730 kernel/workqueue.c:3393
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881088a61c8 of 4 bytes by interrupt on cpu 1:
fprop_reflect_period_percpu+0x32/0x1a0 lib/flex_proportions.c:115
__fprop_add_percpu lib/flex_proportions.c:142 [inline]
__fprop_add_percpu_max+0x58/0x180 lib/flex_proportions.c:200
wb_domain_writeout_add mm/page-writeback.c:560 [inline]
__wb_writeout_add+0x77/0x1d0 mm/page-writeback.c:584
__folio_end_writeback+0x215/0x4a0 mm/page-writeback.c:3042
folio_end_writeback+0x74/0x1f0 mm/filemap.c:1632
mpage_write_end_io+0x281/0x3a0 fs/mpage.c:72
bio_endio+0x369/0x410 block/bio.c:1636
blk_update_request+0x382/0x880 block/blk-mq.c:929
blk_mq_end_request+0x26/0x50 block/blk-mq.c:1057
lo_complete_rq+0xce/0x180 drivers/block/loop.c:389
blk_complete_reqs block/blk-mq.c:1132 [inline]
blk_done_softirq+0x74/0xb0 block/blk-mq.c:1137
handle_softirqs+0xc3/0x280 kernel/softirq.c:554
run_ksoftirqd+0x1c/0x30 kernel/softirq.c:928
smpboot_thread_fn+0x31c/0x4c0 kernel/smpboot.c:164
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000180 -> 0x00000183

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23 Comm: ksoftirqd/1 Tainted: G W 6.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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