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BUG: KCSAN: data-race in ext4_ext_try_to_merge_right / ext4_mark_iloc_dirty

write to 0xffff88810db7e950 of 2 bytes by task 24 on cpu 1:
 ext4_ext_try_to_merge_right+0x285/0x4c0 fs/ext4/extents.c:1768
 ext4_ext_try_to_merge+0x6b/0x310 fs/ext4/extents.c:1852
 ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3721 [inline]
 ext4_ext_handle_unwritten_extents+0x670/0xac0 fs/ext4/extents.c:3849
 ext4_ext_map_blocks+0x728/0x1fd0 fs/ext4/extents.c:4119
 ext4_map_blocks+0x726/0xff0 fs/ext4/inode.c:638
 ext4_convert_unwritten_extents+0x15a/0x2c0 fs/ext4/extents.c:4760
 ext4_convert_unwritten_io_end_vec+0xa4/0x130 fs/ext4/extents.c:4799
 ext4_end_io_end fs/ext4/page-io.c:184 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
 ext4_end_io_rsv_work+0x198/0x360 fs/ext4/page-io.c:271
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88810db7e950 of 4 bytes by task 13090 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:5111 [inline]
 ext4_mark_iloc_dirty+0xcfa/0x16f0 fs/ext4/inode.c:5724
 __ext4_mark_inode_dirty+0x4db/0x5e0 fs/ext4/inode.c:5918
 ext4_dirty_inode+0x86/0xa0 fs/ext4/inode.c:5947
 __mark_inode_dirty+0x72/0x6f0 fs/fs-writeback.c:2274
 mark_inode_dirty include/linux/fs.h:2267 [inline]
 generic_write_end+0x166/0x240 fs/buffer.c:2203
 ext4_da_write_end+0x59b/0x760 fs/ext4/inode.c:3112
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3586
 ext4_buffered_write_iter+0x2e5/0x3e0 fs/ext4/file.c:269
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_writev fs/read_write.c:939 [inline]
 do_pwritev+0x210/0x410 fs/read_write.c:1036
 __do_sys_pwritev fs/read_write.c:1083 [inline]
 __se_sys_pwritev fs/read_write.c:1078 [inline]
 __x64_sys_pwritev+0x54/0x60 fs/read_write.c:1078
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13090 Comm: syz-executor.3 Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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