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BUG: KCSAN: data-race in generic_write_end / mpage_process_page_bufs

write to 0xffff888122482b88 of 8 bytes by task 8895 on cpu 0:
 i_size_write include/linux/fs.h:913 [inline]
 generic_write_end+0x96/0x180 fs/buffer.c:2186
 ext4_da_write_end+0x4de/0x630 fs/ext4/inode.c:3059
 generic_perform_write+0x261/0x400 mm/filemap.c:3767
 ext4_buffered_write_iter+0x25b/0x380 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x1200
 call_write_iter include/linux/fs.h:2162 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x7f5/0x950 fs/read_write.c:590
 ksys_write+0xd9/0x190 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888122482b88 of 8 bytes by task 8879 on cpu 1:
 i_size_read include/linux/fs.h:891 [inline]
 mpage_process_page_bufs+0x34/0x560 fs/ext4/inode.c:2187
 mpage_prepare_extent_to_map+0x4f6/0x650 fs/ext4/inode.c:2621
 ext4_writepages+0xa78/0x1e80 fs/ext4/inode.c:2793
 do_writepages+0x1cb/0x330 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:407 [inline]
 __filemap_fdatawrite_range mm/filemap.c:440 [inline]
 __filemap_fdatawrite mm/filemap.c:446 [inline]
 filemap_flush+0xd7/0x100 mm/filemap.c:473
 ext4_alloc_da_blocks+0x47/0x100 fs/ext4/inode.c:3103
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x160/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xd0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000582000 -> 0x0000000000584000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8879 Comm: syz-executor.1 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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