Re: [PATCH v5 3/9] ovl: Prepare for mounting case-insensitive enabled layers

[Amir Goldstein <amir73il@gmail.com>]

On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>
> Prepare for mounting layers with case-insensitive dentries in order to
> supporting such layers in overlayfs, while enforcing uniform casefold
> layers.
>
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
> Changes from v4:
> - Move relaxation of dentry_weird to the last patch
> - s/filesystems/layerss
> - Commit now says "Prepare for" instead of "Support"
> ---
>  fs/overlayfs/ovl_entry.h |  1 +
>  fs/overlayfs/params.c    | 15 ++++++++++++---
>  fs/overlayfs/params.h    |  1 +
>  3 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
> index 4c1bae935ced274f93a0d23fe10d34455e226ec4..1d4828dbcf7ac4ba9657221e601bbf79d970d225 100644
> --- a/fs/overlayfs/ovl_entry.h
> +++ b/fs/overlayfs/ovl_entry.h
> @@ -91,6 +91,7 @@ struct ovl_fs {
>         struct mutex whiteout_lock;
>         /* r/o snapshot of upperdir sb's only taken on volatile mounts */
>         errseq_t errseq;
> +       bool casefold;
>  };
>
>  /* Number of lower layers, not including data-only layers */
> diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
> index f4e7fff909ac49e2f8c58a76273426c1158a7472..17d2354ba88d92e1d9653e8cb1382d860a7329c5 100644
> --- a/fs/overlayfs/params.c
> +++ b/fs/overlayfs/params.c
> @@ -277,16 +277,25 @@ static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
>                                enum ovl_opt layer, const char *name, bool upper)
>  {
>         struct ovl_fs_context *ctx = fc->fs_private;
> +       struct ovl_fs *ofs = fc->s_fs_info;
> +       bool is_casefolded = ovl_dentry_casefolded(path->dentry);
>
>         if (!d_is_dir(path->dentry))
>                 return invalfc(fc, "%s is not a directory", name);
>
>         /*
>          * Allow filesystems that are case-folding capable but deny composing
> -        * ovl stack from case-folded directories.
> +        * ovl stack from inconsistent case-folded directories.
>          */
> -       if (ovl_dentry_casefolded(path->dentry))
> -               return invalfc(fc, "case-insensitive directory on %s not supported", name);
> +       if (!ctx->casefold_set) {
> +               ofs->casefold = is_casefolded;
> +               ctx->casefold_set = true;
> +       }
> +
> +       if (ofs->casefold != is_casefolded) {
> +               return invalfc(fc, "case-%ssensitive directory on %s is inconsistent",
> +                              is_casefolded ? "in" : "", name);
> +       }
>
>         if (ovl_dentry_weird(path->dentry))
>                 return invalfc(fc, "filesystem on %s not supported", name);
> diff --git a/fs/overlayfs/params.h b/fs/overlayfs/params.h
> index c96d939820211ddc63e265670a2aff60d95eec49..ffd53cdd84827cce827e8852f2de545f966ce60d 100644
> --- a/fs/overlayfs/params.h
> +++ b/fs/overlayfs/params.h
> @@ -33,6 +33,7 @@ struct ovl_fs_context {
>         struct ovl_opt_set set;
>         struct ovl_fs_context_layer *lower;
>         char *lowerdir_all; /* user provided lowerdir string */
> +       bool casefold_set;
>  };
>
>  int ovl_init_fs_context(struct fs_context *fc);
>
> --
> 2.50.1
>