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BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff8881066c2e60 of 8 bytes by task 29855 on cpu 0:
 i_size_write include/linux/fs.h:932 [inline]
 generic_write_end+0x94/0x230 fs/buffer.c:2280
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 generic_perform_write+0x267/0x410 mm/filemap.c:3953
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4037
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4063
 call_write_iter include/linux/fs.h:1985 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4ab/0x7d0 fs/read_write.c:584
 ksys_write+0xeb/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+0x42/0x50 fs/read_write.c:646
 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 0xffff8881066c2e60 of 8 bytes by task 29869 on cpu 1:
 i_size_read include/linux/fs.h:910 [inline]
 __mpage_writepage+0xc0/0xd90 fs/mpage.c:489
 write_cache_pages+0x38d/0x740 mm/page-writeback.c:2474
 mpage_writepages+0x72/0xe0 fs/mpage.c:679
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:390
 __filemap_fdatawrite_range mm/filemap.c:423 [inline]
 filemap_write_and_wait_range+0xe0/0x210 mm/filemap.c:678
 kiocb_write_and_wait mm/filemap.c:2738 [inline]
 generic_file_read_iter+0x101/0x330 mm/filemap.c:2803
 call_read_iter include/linux/fs.h:1979 [inline]
 aio_read+0x1e5/0x2f0 fs/aio.c:1551
 io_submit_one+0xb0b/0x1250 fs/aio.c:2001
 __do_sys_io_submit fs/aio.c:2060 [inline]
 __se_sys_io_submit+0xf5/0x280 fs/aio.c:2030
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2030
 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: 0x00000000000c5000 -> 0x00000000000c6000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29869 Comm: syz-executor.3 Not tainted 6.6.0-rc1-syzkaller-00014-ga747acc0b752 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
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