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BUG: KCSAN: data-race in filemap_fdatawrite_wbc / xas_set_mark

write to 0xffff88815646d144 of 4 bytes by task 27185 on cpu 0:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x131/0x140 lib/xarray.c:892
 tag_pages_for_writeback+0xaa/0x2a0 mm/page-writeback.c:2350
 write_cache_pages+0x1ad/0x740 mm/page-writeback.c:2420
 mpage_writepages+0x72/0xe0 fs/mpage.c:672
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xf4/0x190 mm/filemap.c:779
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1438
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2734 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4055
 call_write_iter include/linux/fs.h:2087 [inline]
 iter_file_splice_write+0x5de/0x950 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x167/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x2fb/0x660 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 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_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88815646d144 of 4 bytes by task 27200 on cpu 1:
 xa_marked include/linux/xarray.h:420 [inline]
 mapping_tagged include/linux/fs.h:509 [inline]
 filemap_fdatawrite_wbc+0x5c/0xf0 mm/filemap.c:384
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xf4/0x190 mm/filemap.c:779
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1438
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2734 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4055
 call_write_iter include/linux/fs.h:2087 [inline]
 iter_file_splice_write+0x5de/0x950 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x167/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x2fb/0x660 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 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_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x04000021 -> 0x1c000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27200 Comm: syz-executor.4 Not tainted 6.8.0-rc7-syzkaller-00130-g135288b73cef #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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