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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff88810821b228 of 8 bytes by interrupt on cpu 1:
 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:2971
 folio_end_writeback_no_dropbehind+0x6d/0x1d0 mm/filemap.c:1667
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1693
 bh_end_async_write+0x1a6/0x250 fs/buffer.c:461
 bio_endio+0x35b/0x3f0 block/bio.c:1790
 blk_update_request+0x338/0x710 block/blk-mq.c:1016
 blk_mq_end_request+0x26/0x50 block/blk-mq.c:1147
 lo_complete_rq+0x98/0x130 drivers/block/loop.c:314
 blk_complete_reqs block/blk-mq.c:1222 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1227
 handle_softirqs+0xb9/0x280 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x42/0xd0 kernel/softirq.c:735
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
 __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:198
 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline]
 rmqueue_bulk mm/page_alloc.c:2543 [inline]
 __rmqueue_pcplist+0x93b/0xb40 mm/page_alloc.c:3329
 rmqueue_pcplist mm/page_alloc.c:3367 [inline]
 rmqueue mm/page_alloc.c:3397 [inline]
 get_page_from_freelist+0x73e/0x1a70 mm/page_alloc.c:3938
 __alloc_frozen_pages_noprof+0x161/0x350 mm/page_alloc.c:5221
 alloc_pages_mpol+0xa9/0x1d0 mm/mempolicy.c:2490
 folio_alloc_mpol_noprof+0x39/0x80 mm/mempolicy.c:2509
 shmem_alloc_folio mm/shmem.c:1931 [inline]
 shmem_alloc_and_add_folio mm/shmem.c:1973 [inline]
 shmem_get_folio_gfp+0x405/0xdc0 mm/shmem.c:2562
 shmem_get_folio mm/shmem.c:2668 [inline]
 shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3302
 generic_perform_write+0x186/0x490 mm/filemap.c:4336
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3477
 lo_rw_aio+0x6a9/0x760 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1921 [inline]
 loop_process_work+0x567/0xac0 drivers/block/loop.c:1956
 loop_workfn+0x31/0x40 drivers/block/loop.c:1980
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3397
 worker_thread+0x569/0x750 kernel/workqueue.c:3478
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88810821b228 of 8 bytes by task 24032 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x211/0x650 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2081 [inline]
 filemap_get_folios_tag+0xf7/0x400 mm/filemap.c:2349
 __filemap_fdatawait_range mm/filemap.c:524 [inline]
 filemap_write_and_wait_range+0x1f5/0x370 mm/filemap.c:693
 filemap_write_and_wait include/linux/pagemap.h:65 [inline]
 sync_blockdev+0x35/0x50 block/bdev.c:276
 loop_set_status+0x110/0x670 drivers/block/loop.c:1241
 loop_set_status_old drivers/block/loop.c:1358 [inline]
 lo_ioctl+0x795/0x1390 drivers/block/loop.c:1547
 blkdev_ioctl+0x387/0x460 block/ioctl.c:797
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff00000000 -> 0xfffff80000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 24032 Comm: syz.3.14195 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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loop7: detected capacity change from 16384 to 0