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BUG: KCSAN: data-race in ext4_ext_insert_extent / ext4_mark_iloc_dirty

write to 0xffff88812535f1dc of 2 bytes by task 16474 on cpu 1:
 ext4_ext_insert_extent+0x1408/0x25c0 fs/ext4/extents.c:2012
 ext4_ext_map_blocks+0xc5c/0x2330 fs/ext4/extents.c:4486
 ext4_map_blocks+0x23a/0xfa0 fs/ext4/inode.c:640
 mpage_map_one_extent fs/ext4/inode.c:2468 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2517 [inline]
 ext4_writepages+0x136e/0x2300 fs/ext4/inode.c:2869
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1c5/0x230 mm/filemap.c:421
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x2d/0x40 mm/filemap.c:456
 ext4_alloc_da_blocks+0x78/0x180 fs/ext4/inode.c:3243
 ext4_release_file+0x10d/0x200 fs/ext4/file.c:88
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812535f1dc of 4 bytes by task 16595 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:5304 [inline]
 ext4_mark_iloc_dirty+0xa32/0x1580 fs/ext4/inode.c:5876
 ext4_mark_inode_dirty+0xe9/0x420 fs/ext4/inode.c:6055
 ext4_dirty_inode+0x86/0xb0 fs/ext4/inode.c:6086
 __mark_inode_dirty+0x5d4/0x940 fs/fs-writeback.c:2258
 mark_inode_dirty include/linux/fs.h:2165 [inline]
 generic_write_end+0x1b7/0x1f0 fs/buffer.c:2159
 ext4_da_write_end+0x158/0x620 fs/ext4/inode.c:3189
 generic_perform_write+0x1d3/0x320 mm/filemap.c:3316
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3434
 ext4_file_write_iter+0x1bd/0xa00 fs/ext4/file.c:268
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16595 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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