[moderation] [mm?] [fs?] upstream test error: KCSAN: data-race in __xa_clear_mark / xas_find_marked (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 98906f9d850e Merge tag 'rtc-6.18' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12434dcd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=bafeb347352dd60e
dashboard link: https://syzkaller.appspot.com/bug?extid=623090df007d361c92e9
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linux-...@vger.kernel.org linu...@kvack.org wi...@infradead.org]

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dd34162453f7/disk-98906f9d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2fc1ead30c12/vmlinux-98906f9d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cbddd584eab7/bzImage-98906f9d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+623090...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff888106e976b8 of 8 bytes by task 1476 on cpu 1:
instrument_read_write include/linux/instrumented.h:55 [inline]
__instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
___test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:114 [inline]
node_clear_mark lib/xarray.c:102 [inline]
xas_clear_mark lib/xarray.c:922 [inline]
__xa_clear_mark+0xf5/0x1e0 lib/xarray.c:2100
__folio_end_writeback+0xf7/0x3b0 mm/page-writeback.c:2998
folio_end_writeback_no_dropbehind+0x6d/0x1b0 mm/filemap.c:1668
folio_end_writeback+0x1c/0x70 mm/filemap.c:1694
ext4_finish_bio+0x459/0x8c0 fs/ext4/page-io.c:144
ext4_release_io_end+0x9f/0x1f0 fs/ext4/page-io.c:159
ext4_end_io_end+0x18d/0x240 fs/ext4/page-io.c:210
ext4_do_flush_completed_IO fs/ext4/page-io.c:290 [inline]
ext4_end_io_rsv_work+0x151/0x1e0 fs/ext4/page-io.c:305
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
worker_thread+0x582/0x770 kernel/workqueue.c:3427
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888106e976b8 of 8 bytes by task 3663 on cpu 0:
xas_find_chunk include/linux/xarray.h:1752 [inline]
xas_find_marked+0x218/0x620 lib/xarray.c:1510
find_get_entry+0x5d/0x380 mm/filemap.c:2070
filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2338
__filemap_fdatawait_range mm/filemap.c:533 [inline]
filemap_fdatawait_keep_errors+0x6c/0x180 mm/filemap.c:636
wait_sb_inodes fs/fs-writeback.c:2754 [inline]
sync_inodes_sb+0x39c/0x440 fs/fs-writeback.c:2876
sync_inodes_one_sb+0x3d/0x50 fs/sync.c:77
__iterate_supers+0x110/0x220 fs/super.c:923
iterate_supers+0x1f/0x30 fs/super.c:938
ksys_sync+0x5c/0xe0 fs/sync.c:102
__ia32_sys_sync+0xe/0x20 fs/sync.c:113
x64_sys_call+0x2d1f/0x3000 arch/x86/include/generated/asm/syscalls_64.h:163
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffffffffff80 -> 0xffffffffffc00000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3663 Comm: syz.1.333 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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