[CRIU] [PATCH 1/2] mnt: add matching on fs kernel subtypes

[Pavel Emelyanov]

On 04/09/2015 08:32 PM, Tycho Andersen wrote:
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  mount.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/mount.c b/mount.c
> index fff7eb4..aec41dc 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -1127,12 +1127,32 @@ struct fstype *find_fstype_by_name(char *fst)
>  	 * anything is wrong, almost every fs has its own features)
>  	 * 2nd -- save some space in the image (since we scan all
>  	 * names anyway)
> +	 *
> +	 * The kernel reports "subtypes" sometimes and the valid
> +	 * type-vs-subtype delimiter is the dot symbol. Here we also collect
> +	 * the subtype if present so we can match against that as well.
>  	 */
> +	char subtype[1024];
> +	bool has_subtype = false;
>  
> -	for (i = 0; i < ARRAY_SIZE(fstypes); i++)
> +	for (i = 0; fst[i] && i < sizeof(subtype) - 1; i++) {
> +		if (fst[i] == '.') {
> +			has_subtype = true;
> +			break;
> +		}
> +		subtype[i] = fst[i];

Thus the subtype is the part of type prior to '.' ...

> +	}
> +
> +	subtype[i] = 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(fstypes); i++) {
>  		if (!strcmp(fstypes[i].name, fst))
>  			return fstypes + i;
>  
> +		if (has_subtype && !strcmp(fstypes[i].name, subtype))
> +			return fstypes + i;

... so for fuse.foo-s we will have two strcmp-s -- one for "fuse.foo" and then
for "fuse", while we only need the 2nd one always.

The subtype (part after dot) is just informational. When we will support fuse
(or any other fs with subtypes) we will have to save the subtype in the image
and pass one back to mount(). Right now we can just throw one away and only
strcmp() on the type (part before dot).

> +	}
> +
>  	return &fstypes[0];
>  }
>  
>