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BUG: KCSAN: data-race in __writeback_single_inode / xas_set_mark

write to 0xffff888109dfd51c of 4 bytes by task 15459 on cpu 1:
 xa_mark_set lib/xarray.c:69 [inline]
 xas_set_mark+0x131/0x140 lib/xarray.c:894
 __folio_start_writeback+0x23f/0x4b0 mm/page-writeback.c:3030
 set_page_writeback+0x46/0xf0 mm/folio-compat.c:51
 __block_write_full_page+0x5b1/0xc70 fs/buffer.c:1860
 block_write_full_page+0x1d8/0x200
 __mpage_writepage+0x761/0xdb0 fs/mpage.c:652
 write_cache_pages+0x3a1/0x760 mm/page-writeback.c:2473
 mpage_writepages+0x72/0xe0 fs/mpage.c:679
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1c5/0x340 mm/page-writeback.c:2551
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:390
 __filemap_fdatawrite_range mm/filemap.c:423 [inline]
 file_write_and_wait_range+0xfa/0x190 mm/filemap.c:781
 __generic_file_fsync+0x4c/0x140 fs/libfs.c:1127
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10b/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2469 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4087
 do_iter_write+0x4ae/0x770 fs/read_write.c:860
 vfs_iter_write+0x50/0x70 fs/read_write.c:901
 iter_file_splice_write+0x456/0x7d0 fs/splice.c:795
 do_splice_from fs/splice.c:873 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1039
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:994
 do_splice_direct+0x104/0x180 fs/splice.c:1082
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888109dfd51c of 4 bytes by task 15461 on cpu 0:
 xa_marked include/linux/xarray.h:420 [inline]
 mapping_tagged include/linux/fs.h:480 [inline]
 __writeback_single_inode+0x21d/0x860 fs/fs-writeback.c:1654
 writeback_single_inode+0x12f/0x4a0 fs/fs-writeback.c:1724
 sync_inode_metadata+0x56/0x80 fs/fs-writeback.c:2780
 __generic_file_fsync+0xf9/0x140 fs/libfs.c:1138
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10b/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2469 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4087
 do_iter_write+0x4ae/0x770 fs/read_write.c:860
 vfs_iter_write+0x50/0x70 fs/read_write.c:901
 iter_file_splice_write+0x456/0x7d0 fs/splice.c:795
 do_splice_from fs/splice.c:873 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1039
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:994
 do_splice_direct+0x104/0x180 fs/splice.c:1082
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x14000021 -> 0x08000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15461 Comm: syz-executor.2 Not tainted 6.4.0-rc3-syzkaller-00171-g9db898594c54 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/16/2023
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