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BUG: KCSAN: data-race in filemap_fdatawrite_wbc / xas_set_mark

write to 0xffff8881139e5d14 of 4 bytes by task 3576 on cpu 1:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x131/0x150 lib/xarray.c:893
 tag_pages_for_writeback+0xa5/0x2a0 mm/page-writeback.c:2420
 writeback_iter+0x351/0x830 mm/page-writeback.c:2563
 write_cache_pages+0x4b/0x100 mm/page-writeback.c:2639
 mpage_writepages+0x72/0xf0 fs/mpage.c:666
 fat_writepages+0x24/0x30 fs/fat/inode.c:199
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2683
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:398
 __filemap_fdatawrite_range mm/filemap.c:431 [inline]
 filemap_write_and_wait_range+0xb9/0x2c0 mm/filemap.c:685
 filemap_invalidate_pages+0xa5/0x1a0 mm/filemap.c:2745
 kiocb_invalidate_pages mm/filemap.c:2764 [inline]
 generic_file_direct_write+0x9d/0x250 mm/filemap.c:3970
 __generic_file_write_iter+0xae/0x120 mm/filemap.c:4141
 generic_file_write_iter+0x77/0x1c0 mm/filemap.c:4181
 iter_file_splice_write+0x5f1/0x980 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x302/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x39b/0x970 fs/read_write.c:1388
 __do_sys_sendfile64 fs/read_write.c:1455 [inline]
 __se_sys_sendfile64 fs/read_write.c:1441 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1441
 x64_sys_call+0xed5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881139e5d14 of 4 bytes by task 3573 on cpu 0:
 xa_marked include/linux/xarray.h:424 [inline]
 mapping_tagged include/linux/fs.h:502 [inline]
 filemap_fdatawrite_wbc+0x5c/0x100 mm/filemap.c:394
 __filemap_fdatawrite_range mm/filemap.c:431 [inline]
 filemap_write_and_wait_range+0xb9/0x2c0 mm/filemap.c:685
 kiocb_write_and_wait mm/filemap.c:2731 [inline]
 generic_file_read_iter+0xff/0x330 mm/filemap.c:2805
 copy_splice_read+0x3a0/0x5d0 fs/splice.c:365
 do_splice_read fs/splice.c:984 [inline]
 splice_direct_to_actor+0x28b/0x670 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x39b/0x970 fs/read_write.c:1388
 __do_sys_sendfile64 fs/read_write.c:1455 [inline]
 __se_sys_sendfile64 fs/read_write.c:1441 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1441
 x64_sys_call+0xed5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x02000021 -> 0x0e000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3573 Comm: syz.4.53 Not tainted 6.12.0-rc1-syzkaller-00349-g8f602276d390 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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