Re: [PATCH v2] erofs: accept source file descriptor via fsconfig

Aleksa Sarai <[email protected]> Tue, 14 Jul 2026 10:49:40 +1000

Newsgroups	org.ozlabs.lists.linux-erofs,org.kernel.vger.linux-fsdevel
Message-ID	<[email protected]>

On 2026-07-13, Giuseppe Scrivano <[email protected]> wrote:
> thanks for the hints.
> 
> I'll prepare a v3 if you are fine with the version below:

No worries, and this seems more reasonable at a first glance.

> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 86fa5c6a0c70..72c85cc53085 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
...
> @@ -437,6 +439,38 @@ static bool erofs_fc_set_dax_mode(struct fs_context *fc, unsigned int mode)
>  	return false;
>  }
>  
> +static int erofs_fc_parse_source(struct fs_context *fc,
> +				 struct fs_parameter *param)
> +{
> +	struct erofs_sb_info *sbi = fc->s_fs_info;
> +
> +	if (fc->source || sbi->dif0.file)
> +		return invalf(fc, "Multiple sources");
> +
> +	switch (param->type) {
> +	case fs_value_is_string:
> +		fc->source = param->string;
> +		param->string = NULL;
> +		return 0;
> +	case fs_value_is_file: {
> +		char *buf, *p;
> +
> +		sbi->dif0.file = get_file(param->file);

A very minor nit, but you can actually steal the file reference here
with

		sbi->dif0.file = no_free_ptr(param->file);

A few other places do this. (You'll also need to change the param->file
reference below.)

> +		buf = kmalloc(PATH_MAX, GFP_KERNEL);
> +		if (!buf)
> +			return -ENOMEM;
> +		p = file_path(param->file, buf, PATH_MAX);
> +		fc->source = kstrdup(IS_ERR(p) ? "(fd)" : p, GFP_KERNEL);

I think that /proc/self/fd/%d would be a more useful name for debugging
if file_path() fails (not that it is really possible here AFAICS). But
I'm not really too fussed.

-- 
Aleksa Sarai
Founding Engineer at Amutable
https://www.cyphar.com/

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