linux-kernel - Re: [PATCH v6 3/9] ovl: Prepare for mounting case-insensitive enabled layers

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Message-ID: <87a53n65sk.fsf@mailhost.krisman.be>
Date: Mon, 25 Aug 2025 06:42:51 -0400
From: Gabriel Krisman Bertazi <gabriel@...sman.be>
To: André Almeida <andrealmeid@...lia.com>
Cc: Miklos Szeredi <miklos@...redi.hu>,  Amir Goldstein
 <amir73il@...il.com>,  Theodore Tso <tytso@....edu>,
  linux-unionfs@...r.kernel.org,  linux-kernel@...r.kernel.org,
  linux-fsdevel@...r.kernel.org,  Alexander Viro <viro@...iv.linux.org.uk>,
  Christian Brauner <brauner@...nel.org>,  Jan Kara <jack@...e.cz>,
  kernel-dev@...lia.com
Subject: Re: [PATCH v6 3/9] ovl: Prepare for mounting case-insensitive
 enabled layers

André Almeida <andrealmeid@...lia.com> writes:

> Prepare for mounting layers with case-insensitive dentries in order to
> supporting such layers in overlayfs, while enforcing uniform casefold
> layers.
>
> Reviewed-by: Amir Goldstein <amir73il@...il.com>
> Signed-off-by: André Almeida <andrealmeid@...lia.com>


Reviewed-by: Gabriel Krisman Bertazi <gabriel@...sman.be>

> ---
>  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..63b7346c5ee1c127a9c33b12c3704aa035ff88cf 100644
> --- a/fs/overlayfs/params.c
> +++ b/fs/overlayfs/params.c
> @@ -276,17 +276,26 @@ static int ovl_mount_dir(const char *name, struct path *path)
>  static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
>  			       enum ovl_opt layer, const char *name, bool upper)
>  {
> +	bool is_casefolded = ovl_dentry_casefolded(path->dentry);
>  	struct ovl_fs_context *ctx = fc->fs_private;
> +	struct ovl_fs *ofs = fc->s_fs_info;
>  
>  	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);

-- 
Gabriel Krisman Bertazi