On Mon, Jun 02, 2025 at 07:17:02PM +0200, Amir Goldstein wrote: > Case folding is often applied to subtrees and not on an entire > filesystem. > > Disallowing layers from filesystems that support case folding is over > limiting. > > Replace the rule that case-folding capable are not allowed as layers > with a rule that case folded directories are not allowed in a merged > directory stack. > > Should case folding be enabled on an underlying directory while > overlayfs is mounted the outcome is generally undefined. > > Specifically in ovl_lookup(), we check the base underlying directory > and fail with -ESTALE and write a warning to kmsg if an underlying > directory case folding is enabled. > > Suggested-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> > Link: https://lore.kernel.org/linux-fsdevel/20250520051600.1903319-1-kent.overstreet@xxxxxxxxx/ > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > --- > > Miklos, > > This is my solution to Kent's request to allow overlayfs mount on > bcachefs subtrees that do not have casefolding enabled, while other > subtrees do have casefolding enabled. > > I have written a test to cover the change of behavior [1]. > This test does not run on old kernel's where the mount always fails > with casefold capable layers. > > Let me know what you think. > > Kent, > > I have tested this on ext4. > Please test on bcachefs. Where are we at with getting this in? I've got users who keep asking, so hoping we can get it backported to 6.15
