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BUG: KCSAN: data-race in __writeback_single_inode / xas_set_mark

write to 0xffff888109049d64 of 4 bytes by task 3331 on cpu 0:
 xa_mark_set lib/xarray.c:71 [inline]
 xas_set_mark+0x131/0x150 lib/xarray.c:892
 __folio_start_writeback+0x1f1/0x450 mm/page-writeback.c:3062
 __mpage_writepage+0xbed/0xe10 fs/mpage.c:626
 write_cache_pages+0x62/0x100 mm/page-writeback.c:2570
 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:2613
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:397
 __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:1516
 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:2811 [inline]
 generic_file_write_iter+0x191/0x1d0 mm/filemap.c:4099
 call_write_iter include/linux/fs.h:2120 [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
 x64_sys_call+0x2c67/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:41
 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+0x77/0x7f

read to 0xffff888109049d64 of 4 bytes by task 3332 on cpu 1:
 xa_marked include/linux/xarray.h:420 [inline]
 mapping_tagged include/linux/fs.h:496 [inline]
 __writeback_single_inode+0x21d/0x870 fs/fs-writeback.c:1702
 writeback_single_inode+0x12f/0x4a0 fs/fs-writeback.c:1772
 sync_inode_metadata+0x5c/0x90 fs/fs-writeback.c:2842
 __generic_file_fsync+0xf9/0x140 fs/libfs.c:1527
 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:2811 [inline]
 generic_file_write_iter+0x191/0x1d0 mm/filemap.c:4099
 call_write_iter include/linux/fs.h:2120 [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
 x64_sys_call+0x2c67/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:41
 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+0x77/0x7f

value changed: 0x05000021 -> 0x02000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3332 Comm: syz-executor.3 Not tainted 6.9.0-syzkaller-08995-g0450d2083be6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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