syzbot

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BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked

read-write to 0xffff888106b83fd0 of 8 bytes by task 7787 on cpu 0:
 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+0x2ce/0x440 mm/page-writeback.c:3090
 mpage_write_folio fs/mpage.c:615 [inline]
 mpage_writepages+0xd18/0x1250 fs/mpage.c:664
 fat_writepages+0x24/0x30 fs/fat/inode.c:199
 do_writepages+0x1c3/0x310 mm/page-writeback.c:2636
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x156/0x2c0 mm/filemap.c:794
 __generic_file_fsync+0x46/0x140 fs/libfs.c:1526
 fat_file_fsync+0x49/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10d/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3031 [inline]
 generic_file_write_iter+0x1b8/0x2f0 mm/filemap.c:4259
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x4a0/0x8e0 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2cdd/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:2
 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

read to 0xffff888106b83fd0 of 8 bytes by task 270 on cpu 1:
 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:2038
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2306
 writeback_get_folio mm/page-writeback.c:2463 [inline]
 writeback_iter+0x4bb/0x820 mm/page-writeback.c:2564
 mpage_writepages+0x718/0x1250 fs/mpage.c:663
 fat_writepages+0x24/0x30 fs/fat/inode.c:199
 do_writepages+0x1c3/0x310 mm/page-writeback.c:2636
 __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:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x003ffffff8000000 -> 0x003fffffe0000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 270 Comm: kworker/u8:5 Not tainted 6.16.0-rc5-syzkaller-00038-g733923397fd9 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: writeback wb_workfn (flush-7:1)
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