loop7: detected capacity change from 0 to 16384
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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88813646fd90 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
 end_buffer_async_write+0x156/0x1f0 fs/buffer.c:416
 end_bio_bh_io_sync+0x79/0xa0 fs/buffer.c:2773
 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
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x39/0xc0 kernel/softirq.c:723
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
 _raw_spin_unlock_irqrestore+0x1a/0x30 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:407 [inline]
 unlock_page_lruvec_irqrestore include/linux/memcontrol.h:1495 [inline]
 folio_batch_move_lru+0x22f/0x270 mm/swap.c:178
 __folio_batch_add_and_move mm/swap.c:196 [inline]
 folio_add_lru+0x149/0x1e0 mm/swap.c:511
 shmem_alloc_and_add_folio mm/shmem.c:2031 [inline]
 shmem_get_folio_gfp+0x7b0/0xd60 mm/shmem.c:2567
 shmem_get_folio mm/shmem.c:2673 [inline]
 shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3327
 generic_perform_write+0x183/0x490 mm/filemap.c:4319
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3502
 lo_rw_aio+0x67d/0x730 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1925 [inline]
 loop_process_work+0x56c/0xac0 drivers/block/loop.c:1960
 loop_workfn+0x31/0x40 drivers/block/loop.c:1984
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0x513/0xa10 kernel/workqueue.c:3359
 worker_thread+0x58a/0x780 kernel/workqueue.c:3440
 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 0xffff88813646fd90 of 8 bytes by task 2399 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_write_and_wait_range+0x1f5/0x370 mm/filemap.c:692
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev block/bdev.c:276 [inline]
 bdev_release+0xeb/0x3d0 block/bdev.c:1142
 blkdev_release+0x15/0x20 block/fops.c:705
 __fput+0x29b/0x650 fs/file_table.c:469
 ____fput+0x1c/0x30 fs/file_table.c:497
 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: 0xfffffffffffff000 -> 0xfffffffffffc0000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2399 Comm: syz.0.6788 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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