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BUG: KCSAN: data-race in filemap_fdatawrite_wbc / xas_set_mark

write to 0xffff8881086a144c of 4 bytes by task 31094 on cpu 1:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x131/0x150 lib/xarray.c:892
 tag_pages_for_writeback+0xaa/0x2b0 mm/page-writeback.c:2350
 writeback_iter+0x351/0x830 mm/page-writeback.c:2493
 write_cache_pages+0x4b/0x100 mm/page-writeback.c:2568
 mpage_writepages+0x72/0xf0 fs/mpage.c:673
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2612
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:397
 __filemap_fdatawrite_range mm/filemap.c:430 [inline]
 filemap_write_and_wait_range+0xb6/0x1f0 mm/filemap.c:685
 kiocb_invalidate_pages+0x87/0x1e0 mm/filemap.c:2703
 generic_file_direct_write+0x58/0x200 mm/filemap.c:3892
 __generic_file_write_iter+0xae/0x120 mm/filemap.c:4055
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4095
 call_write_iter include/linux/fs.h:2110 [inline]
 iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x970 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

read to 0xffff8881086a144c of 4 bytes by task 31086 on cpu 0:
 xa_marked include/linux/xarray.h:420 [inline]
 mapping_tagged include/linux/fs.h:500 [inline]
 filemap_fdatawrite_wbc+0x5c/0x100 mm/filemap.c:393
 __filemap_fdatawrite_range mm/filemap.c:430 [inline]
 file_write_and_wait_range+0xc8/0x170 mm/filemap.c:788
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1473
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x122/0x140 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2795 [inline]
 generic_file_write_iter+0x191/0x1d0 mm/filemap.c:4099
 call_write_iter include/linux/fs.h:2110 [inline]
 iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x970 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

value changed: 0x01000021 -> 0x02000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 31086 Comm: syz-executor.1 Tainted: G        W          6.9.0-rc2-syzkaller-00385-g104db052b62d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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