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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff88811b974fe8 of 8 bytes by task 51 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+0x91/0x180 lib/xarray.c:922
 __folio_start_writeback+0x2e7/0x430 mm/page-writeback.c:3115
 __block_write_full_folio+0x53a/0x8f0 fs/buffer.c:1934
 block_write_full_folio+0x29c/0x2c0 fs/buffer.c:-1
 write_cache_pages+0x61/0x100 mm/page-writeback.c:2613
 blkdev_writepages+0x58/0x90 block/fops.c:458
 do_writepages+0x1d2/0x480 mm/page-writeback.c:2656
 __writeback_single_inode+0x80/0x7c0 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x480/0xa20 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0x94/0x1a0 fs/fs-writeback.c:2047
 wb_writeback+0x266/0x5c0 fs/fs-writeback.c:2158
 wb_check_start_all fs/fs-writeback.c:2284 [inline]
 wb_do_writeback fs/fs-writeback.c:2310 [inline]
 wb_workfn+0x4c9/0x910 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811b974fe8 of 8 bytes by task 11007 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1746 [inline]
 xas_find_marked+0x218/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2027
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2295
 writeback_get_folio mm/page-writeback.c:2462 [inline]
 writeback_iter+0x4bb/0x820 mm/page-writeback.c:2563
 write_cache_pages+0xad/0x100 mm/page-writeback.c:2612
 blkdev_writepages+0x58/0x90 block/fops.c:458
 do_writepages+0x1d2/0x480 mm/page-writeback.c:2656
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 __filemap_fdatawrite mm/filemap.c:425 [inline]
 filemap_fdatawrite+0xec/0x120 mm/filemap.c:430
 sync_bdevs+0x1a2/0x260 block/bdev.c:1300
 ksys_sync+0x81/0xe0 fs/sync.c:105
 __ia32_sys_sync+0xe/0x20 fs/sync.c:113
 x64_sys_call+0x2e53/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffffff8 -> 0xffffffffffffffe0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11007 Comm: syz.3.2829 Not tainted 6.15.0-rc4-syzkaller-00011-gf15d97df5afa #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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SELinux: unrecognized netlink message: protocol=6 nlmsg_type=2560 sclass=netlink_xfrm_socket pid=11007 comm=syz.3.2829
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=5136 sclass=netlink_xfrm_socket pid=11007 comm=syz.3.2829