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BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff88810af89728 of 8 bytes by task 5930 on cpu 1:
 i_size_write include/linux/fs.h:888 [inline]
 generic_write_end+0xb4/0x360 fs/buffer.c:2211
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3937
 __generic_file_write_iter+0xe6/0x290 mm/filemap.c:4054
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4086
 do_iter_write+0x418/0x700 fs/read_write.c:861
 vfs_iter_write+0x50/0x70 fs/read_write.c:902
 iter_file_splice_write+0x456/0x7d0 fs/splice.c:778
 do_splice_from fs/splice.c:856 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1022
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:977
 do_splice_direct+0x104/0x180 fs/splice.c:1065
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1309
 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 0xffff88810af89728 of 8 bytes by task 5946 on cpu 0:
 i_size_read include/linux/fs.h:866 [inline]
 __mpage_writepage+0xbf/0xda0 fs/mpage.c:463
 write_cache_pages+0x39b/0x760 mm/page-writeback.c:2473
 mpage_writepages+0x72/0xe0 fs/mpage.c:653
 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+0xa1/0xd0 mm/filemap.c:423
 sync_file_range+0x1ad/0x220 fs/sync.c:292
 ksys_sync_file_range fs/sync.c:364 [inline]
 __do_sys_sync_file_range fs/sync.c:373 [inline]
 __se_sys_sync_file_range fs/sync.c:370 [inline]
 __x64_sys_sync_file_range+0x80/0xd0 fs/sync.c:370
 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: 0x0000000000067000 -> 0x0000000000068000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5946 Comm: syz-executor.2 Not tainted 6.3.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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