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BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff888109b17ce8 of 8 bytes by task 4847 on cpu 0:
 i_size_write include/linux/fs.h:905 [inline]
 generic_write_end+0xb4/0x360 fs/buffer.c:2241
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3934
 __generic_file_write_iter+0xe6/0x290 mm/filemap.c:4051
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4083
 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 0xffff888109b17ce8 of 8 bytes by task 34 on cpu 1:
 i_size_read include/linux/fs.h:883 [inline]
 __mpage_writepage+0xc3/0xdb0 fs/mpage.c:489
 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
 __writeback_single_inode+0x91/0x860 fs/fs-writeback.c:1603
 writeback_sb_inodes+0x511/0xaa0 fs/fs-writeback.c:1894
 wb_writeback+0x23b/0x6c0 fs/fs-writeback.c:2068
 wb_do_writeback fs/fs-writeback.c:2211 [inline]
 wb_workfn+0x1a8/0x8d0 fs/fs-writeback.c:2251
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2405
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2552
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x00000000002f2000 -> 0x00000000002f2278

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 34 Comm: kworker/u4:2 Not tainted 6.4.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Workqueue: writeback wb_workfn (flush-7:3)
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