syzbot

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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88811a8f2908 of 8 bytes by interrupt on cpu 0:
 instrument_read_write include/linux/instrumented.h:56 [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+0xf4/0x360 mm/page-writeback.c:2948
 folio_end_writeback_no_dropbehind+0x6d/0x1d0 mm/filemap.c:1666
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1692
 ext4_finish_bio+0x459/0x8b0 fs/ext4/page-io.c:145
 ext4_end_bio+0x27b/0x380 fs/ext4/page-io.c:393
 bio_endio+0x38a/0x420 block/bio.c:1792
 blk_update_request+0x338/0x740 block/blk-mq.c:1016
 blk_mq_end_request+0x26/0x50 block/blk-mq.c:1178
 lo_complete_rq+0x98/0x140 drivers/block/loop.c:314
 blk_complete_reqs block/blk-mq.c:1253 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1258
 handle_softirqs+0xb9/0x2a0 kernel/softirq.c:622
 run_ksoftirqd+0x1c/0x30 kernel/softirq.c:1063
 smpboot_thread_fn+0x32a/0x510 kernel/smpboot.c:160
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811a8f2908 of 8 bytes by task 3321 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2069 [inline]
 filemap_get_folios_tag+0xfa/0x510 mm/filemap.c:2337
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x190 mm/filemap.c:626
 wait_sb_inodes fs/fs-writeback.c:2805 [inline]
 sync_inodes_sb+0x40e/0x4c0 fs/fs-writeback.c:2927
 sync_filesystem+0x102/0x190 fs/sync.c:64
 generic_shutdown_super+0x4c/0x220 fs/super.c:625
 kill_block_super+0x2a/0x70 fs/super.c:1725
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7459
 deactivate_locked_super+0x75/0x1c0 fs/super.c:476
 deactivate_super+0x97/0xa0 fs/super.c:509
 cleanup_mnt+0x2bb/0x330 fs/namespace.c:1312
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1319
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x003ffffffffffffe -> 0x003fffffffffff80

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3321 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.