Re: [PATCH v3 00/21] ovl: narrow regions protected by i_rw_sem

[Amir Goldstein <amir73il@gmail.com>]

On Wed, Jul 16, 2025 at 2:47 AM NeilBrown <neil@brown.name> wrote:
>
> More excellent review feedback - more patches :-)
>
> I've chosen to use ovl_parent_lock() here as a temporary and leave the
> debate over naming for the VFS version of the function until all the new
> names are introduced later.

Perfect.

Please push v3 patches to branch pdirops, or to a clean branch
based on vfs-6.17.file, so I can test them.

Thanks,
Amir.


>
>
> Original description:
>
> This series of patches for overlayfs is primarily focussed on preparing
> for some proposed changes to directory locking.  In the new scheme we
> will lock individual dentries in a directory rather than the whole
> directory.
>
> ovl currently will sometimes lock a directory on the upper filesystem
> and do a few different things while holding the lock.  This is
> incompatible with the new scheme.
>
> This series narrows the region of code protected by the directory lock,
> taking it multiple times when necessary.  This theoretically open up the
> possibilty of other changes happening on the upper filesytem between the
> unlock and the lock.  To some extent the patches guard against that by
> checking the dentries still have the expect parent after retaking the
> lock.  In general, I think ovl would have trouble if upperfs were being
> changed independantly, and I don't think the changes here increase the
> problem in any important way.
>
> After this series (with any needed changes) lands I will resubmit my
> change to vfs_rmdir() behaviour to have it drop the lock on error.  ovl
> will be much better positioned to handle that change.  It will come with
> the new "lookup_and_lock" API that I am proposing.
>
> Thanks,
> NeilBrown
>
>  [PATCH v3 01/21] ovl: simplify an error path in ovl_copy_up_workdir()
>  [PATCH v3 02/21] ovl: change ovl_create_index() to take dir locks
>  [PATCH v3 03/21] ovl: Call ovl_create_temp() without lock held.
>  [PATCH v3 04/21] ovl: narrow the locked region in
>  [PATCH v3 05/21] ovl: narrow locking in ovl_create_upper()
>  [PATCH v3 06/21] ovl: narrow locking in ovl_clear_empty()
>  [PATCH v3 07/21] ovl: narrow locking in ovl_create_over_whiteout()
>  [PATCH v3 08/21] ovl: simplify gotos in ovl_rename()
>  [PATCH v3 09/21] ovl: narrow locking in ovl_rename()
>  [PATCH v3 10/21] ovl: narrow locking in ovl_cleanup_whiteouts()
>  [PATCH v3 11/21] ovl: narrow locking in ovl_cleanup_index()
>  [PATCH v3 12/21] ovl: narrow locking in ovl_workdir_create()
>  [PATCH v3 13/21] ovl: narrow locking in ovl_indexdir_cleanup()
>  [PATCH v3 14/21] ovl: narrow locking in ovl_workdir_cleanup_recurse()
>  [PATCH v3 15/21] ovl: change ovl_workdir_cleanup() to take dir lock
>  [PATCH v3 16/21] ovl: narrow locking on ovl_remove_and_whiteout()
>  [PATCH v3 17/21] ovl: change ovl_cleanup_and_whiteout() to take
>  [PATCH v3 18/21] ovl: narrow locking in ovl_whiteout()
>  [PATCH v3 19/21] ovl: narrow locking in ovl_check_rename_whiteout()
>  [PATCH v3 20/21] ovl: change ovl_create_real() to receive dentry
>  [PATCH v3 21/21] ovl: rename ovl_cleanup_unlocked() to ovl_cleanup()