Re: [PATCH] libkmod-module: Remove directory existence check for KMOD_MODULE_BUILTIN

Lucas De Marchi
2015-02-19T12:43:43Z

On Thu, Feb 19, 2015 at 10:32 AM, Harish Jenny Kandiga Nagaraj
<harish_kandiga@mentor.com> wrote:
>
> On Thursday 19 February 2015 04:00 PM, Lucas De Marchi wrote:
>> On Thu, Feb 19, 2015 at 3:49 AM, Harish Jenny Kandiga Nagaraj
>> <harish_kandiga@mentor.com> wrote:
>>>> Harrish, in your patch if you just change the "return
>>>> KMOD_MODULE_BUILTIN;" to "return KMOD_MODULE_COMING;" does it work?
>>> Yes. Returning KMOD_MODULE_COMING instead of KMOD_MODULE_BUILTIN works. The built-in modules are handled by looking at the modules.builtin index file. Is there any chance of returning KMOD_MODULE_COMING for builti-in modules? If it does not have any impact, then the fix should be fine.
>> well... you're not returning KMOD_MODULE_COMING for a builtin module.
>> Having the directory /sys/module/<name> and not the initstate could be
>> either that the module is builtin or that there's a race while loading
>> the module and it's in the coming state. However since we use the
>> index to decide if this module is builtin in the beginning of this
>> function, here it can only be the second case.
>>
>> However... mod->builtin in the beginning of this function is only set
>> if the module is created by a lookup rather than from name or from
>> path.... maybe here we need to actually fallback to the index rather
>> than the cached value, otherwise this test would fail (considering
>> "vt" is builtin):
>>
>> kmod_module_new_from_name(ctx, "vt", &mod);
>> kmod_module_get_initstate(mod, &state);
>>
>
>
>
> something like this ?
>
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 19bb2ed..d424f3e 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -99,6 +99,8 @@ struct kmod_module {
> * "module", except knowing it's builtin.
> */
> bool builtin : 1;
> +
> + bool lookup : 1;
> };
>
> static inline const char *path_join(const char *path, size_t prefixlen,
> @@ -215,6 +217,11 @@ void kmod_module_set_builtin(struct kmod_module *mod, bool builtin)
> mod->builtin = builtin;
> }
>
> +void kmod_module_set_lookup(struct kmod_module *mod, bool lookup)
> +{
> + mod->lookup = lookup;
> +}
> +
> void kmod_module_set_required(struct kmod_module *mod, bool required)
> {
> mod->required = required;
> @@ -1729,7 +1736,7 @@ KMOD_EXPORT int kmod_module_get_initstate(const struct kmod_module *mod)
> struct stat st;
> path[pathlen - (sizeof("/initstate") - 1)] = '\0';
> if (stat(path, &st) == 0 && S_ISDIR(st.st_mode))
> - return KMOD_MODULE_COMING;
> + return mod->lookup ? KMOD_MODULE_COMING : KMOD_MODULE_BUILTIN;

no. I guess this doesn't pass the proposed test:

1)
kmod_module_new_from_name(ctx, "vt", &mod);
kmod_module_get_initstate(mod, &state);

this must return builtin

2)
kmod_module_new_from_lookup(ctx, "vt", &list);
... (get mod from list)
kmod_module_get_initstate(mod, &state);

this must return builtin as well.

I suggest you add a kmod_module_is_builtin() which does the lookup
(but doesn't increase the module refcount, i.e. doesn't call
new_module_xxxx()) iff it's not already done. For this you will need
to change mod->builtin to an enum: enum { XXXX_UNKNOWN, XXXX_NO,
XXXX_YES } then you do:

bool kmod_module_is_builtin(mod) (don't export this function)
{
if (mod->XXXX_UNKNOWN) {
... lookup in builtin index
}
return mod->builtin == XXXX_YES;
}

then you change the users of mod->builtin.

--
Lucas De Marchi