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BUG: KCSAN: data-race in __mpage_writepage / truncate_setsize

write to 0xffff888106624980 of 8 bytes by task 4642 on cpu 1:
 i_size_write include/linux/fs.h:871 [inline]
 truncate_setsize+0x2a/0xc0 mm/truncate.c:763
 fat_setattr+0x69a/0x7d0 fs/fat/file.c:538
 notify_change+0x8a3/0xa80 fs/attr.c:398
 do_truncate+0xe8/0x130 fs/open.c:64
 handle_truncate fs/namei.c:3017 [inline]
 do_open fs/namei.c:3365 [inline]
 path_openat+0x1a79/0x20b0 fs/namei.c:3494
 do_filp_open+0xd9/0x1f0 fs/namei.c:3521
 do_sys_openat2+0xa3/0x250 fs/open.c:1187
 do_sys_open fs/open.c:1203 [inline]
 __do_sys_openat fs/open.c:1219 [inline]
 __se_sys_openat fs/open.c:1214 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1214
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888106624980 of 8 bytes by task 4630 on cpu 0:
 i_size_read include/linux/fs.h:849 [inline]
 __mpage_writepage+0x93/0x1080 fs/mpage.c:499
 write_cache_pages+0x4d7/0x810 mm/page-writeback.c:2246
 mpage_writepages+0x6d/0x120 fs/mpage.c:712
 fat_writepages+0x20/0x30 fs/fat/inode.c:205
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range mm/filemap.c:413 [inline]
 file_write_and_wait_range+0x180/0x210 mm/filemap.c:792
 __generic_file_fsync+0x48/0x140 fs/libfs.c:1079
 fat_file_fsync+0x48/0x100 fs/fat/file.c:190
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2982 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3825
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000000000fea7 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4630 Comm: syz-executor.0 Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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attempt to access beyond end of device
loop0: rw=2049, want=144, limit=16