It might check if the cluster numbers are same between source entry
and target directory.
This checks if newdir is the move target itself.
Example:
mv /mnt/dir0 /mnt/dir0/foo
However, this check is not enough.
We need to check newdir and all ancestors.
Example:
mv /mnt/dir0 /mnt/dir0/dir1/foo
mv /mnt/dir0 /mnt/dir0/dir1/dir2/foo
...
This is probably a taboo for all layered filesystems.
Could you let me know what code you mentioned?
Or do you mean the codes on vfs?
You can find in do_renameat2(). --- around 'fs/namei.c:4440'
If the destination ancestors are itself, our driver will not be called.
I think, of course, vfs has been doing that.
So that code is unnecessary in normal situations.
That code comes from the old exfat implementation.
It could be a remnant of another system.
Once upon a time, I moved the dir to a descendant dir without implementing this check
and it disappeared forever.
linux-VFS fixed this issue immediately, but some systems still need to be checked by
the driver itself. (ex.Windows-IFS)
And as far as I understand, it seems to check once more "the cluster number"
even though it comes through vfs so that it tries detecting abnormal of on-disk.
Anyway, I agonized if it is really needed.
In conclusion, old code could be eliminated and your patch looks reasonable.
It's easy to add, but it's really hard to remove the ancient code.
BTW
I have a question for you.
Now, I'm trying to optimize exfat_get_dentry().
However, exfat_get_dentry() is used a lot, so the patch is also large.
In such a case
-Replace old implementation with new ones with a single patch.
-Devide multiple patches in which old functions and new functions (ex. exfat_get_dentry2) coexist temporarily. And finally clean up.
I understand that a small patch is desirable, but the latter has "two similar functions".
Which is better for you to review the patch?
BR
---
Tetsuhiro Kohada <kohada.t2@xxxxxxxxx>
