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BUG: KCSAN: data-race in ext4_ext_try_to_merge_right / ext4_mark_iloc_dirty

write to 0xffff8880909831c2 of 2 bytes by task 23187 on cpu 1:
 le16_add_cpu include/linux/byteorder/generic.h:146 [inline]
 ext4_ext_try_to_merge_right+0x15a/0x2a0 fs/ext4/extents.c:1768
 ext4_ext_try_to_merge+0x337/0x360 fs/ext4/extents.c:1842
 ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3710 [inline]
 ext4_ext_handle_unwritten_extents+0x291/0x18c0 fs/ext4/extents.c:3837
 ext4_ext_map_blocks+0xa7e/0x1fb0 fs/ext4/extents.c:4098
 ext4_map_blocks+0x230/0xcf0 fs/ext4/inode.c:621
 ext4_convert_unwritten_extents+0x18b/0x3b0 fs/ext4/extents.c:4729
 ext4_convert_unwritten_io_end_vec+0xe0/0x1b0 fs/ext4/extents.c:4764
 ext4_end_io_end fs/ext4/page-io.c:187 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:260 [inline]
 ext4_end_io_rsv_work+0x2c2/0x400 fs/ext4/page-io.c:274
 process_one_work+0x424/0x930 kernel/workqueue.c:2268
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2414
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880909831c0 of 4 bytes by task 529 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:5023 [inline]
 ext4_mark_iloc_dirty+0xa37/0x1580 fs/ext4/inode.c:5603
 ext4_mark_inode_dirty+0xe6/0x420 fs/ext4/inode.c:5796
 ext4_dirty_inode+0xad/0xd0 fs/ext4/inode.c:5827
 __mark_inode_dirty+0x5b7/0x940 fs/fs-writeback.c:2258
 mark_inode_dirty include/linux/fs.h:2189 [inline]
 generic_write_end+0x24c/0x290 fs/buffer.c:2193
 ext4_da_write_end+0x162/0x690 fs/ext4/inode.c:3090
 generic_perform_write+0x1d7/0x320 mm/filemap.c:3313
 ext4_buffered_write_iter+0x14e/0x280 fs/ext4/file.c:270
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write+0x303/0x400 fs/read_write.c:484
 __vfs_write+0x9e/0xb0 fs/read_write.c:497
 vfs_write fs/read_write.c:559 [inline]
 vfs_write+0x189/0x380 fs/read_write.c:543
 ksys_write+0xc5/0x1a0 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x49/0x60 fs/read_write.c:621
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 529 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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