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BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff88810a996d28 of 8 bytes by task 8808 on cpu 0:
 i_size_write include/linux/fs.h:886 [inline]
 generic_write_end+0xb1/0x350 fs/buffer.c:2168
 fat_write_end+0x4a/0x150 fs/fat/inode.c:244
 generic_perform_write+0x264/0x3f0 mm/filemap.c:3783
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3900
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3932
 call_write_iter include/linux/fs.h:2186 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88810a996d28 of 8 bytes by task 8809 on cpu 1:
 i_size_read include/linux/fs.h:864 [inline]
 __mpage_writepage+0xb8/0xda0 fs/mpage.c:469
 write_cache_pages+0x443/0xa30 mm/page-writeback.c:2472
 mpage_writepages+0x6e/0xe0 fs/mpage.c:664
 fat_writepages+0x20/0x30 fs/fat/inode.c:200
 do_writepages+0x1db/0x350 mm/page-writeback.c:2581
 filemap_fdatawrite_wbc+0xd6/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xf2/0x190 mm/filemap.c:777
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1132
 fat_file_fsync+0x48/0x100 fs/fat/file.c:191
 vfs_fsync_range fs/sync.c:188 [inline]
 vfs_fsync fs/sync.c:202 [inline]
 do_fsync fs/sync.c:212 [inline]
 __do_sys_fdatasync fs/sync.c:225 [inline]
 __se_sys_fdatasync fs/sync.c:223 [inline]
 __x64_sys_fdatasync+0x7a/0xd0 fs/sync.c:223
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000061a000 -> 0x000000000061c000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8809 Comm: syz-executor.5 Not tainted 6.2.0-rc1-syzkaller-00084-gc8451c141e07-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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