linux-kernel - Re: [PATCH v2 2/2] module: Merge same-name module load requests

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Message-ID: <Y277Jb9i2VeXQoTL@bombadil.infradead.org>
Date:   Fri, 11 Nov 2022 17:47:17 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Prarit Bhargava <prarit@...hat.com>,
        David Hildenbrand <david@...hat.com>
Cc:     pmladek@...e.com, Petr Pavlu <petr.pavlu@...e.com>,
        linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        mcgrof@...nel.org
Subject: Re: [PATCH v2 2/2] module: Merge same-name module load requests

On Wed, Oct 19, 2022 at 02:00:55PM +0200, Petr Pavlu wrote:
> On 10/18/22 20:33, Luis Chamberlain wrote:
> > On Sat, Oct 15, 2022 at 11:27:10AM +0200, Petr Pavlu wrote:
> >> The patch does address a regression observed after commit 6e6de3dee51a
> >> ("kernel/module.c: Only return -EEXIST for modules that have finished
> >> loading"). I guess it can have a Fixes tag added to the patch.
> >>
> >> I think it is hard to split this patch into parts because the implemented
> >> "optimization" is the fix.
> > 
> > git describe --contains 6e6de3dee51a
> > v5.3-rc1~38^2~6
> > 
> > I'm a bit torn about this situation. Reverting 6e6de3dee51a would be the
> > right thing to do, but without it, it still leaves the issue reported
> > by Prarit Bhargava. We need a way to resolve the issue on stable and
> > then your optimizations can be applied on top.
> 
> Simpler could be to do the following:
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index d02d39c7174e..0302ac387e93 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2386,7 +2386,8 @@ static bool finished_loading(const char *name)
>  	sched_annotate_sleep();
>  	mutex_lock(&module_mutex);
>  	mod = find_module_all(name, strlen(name), true);
> -	ret = !mod || mod->state == MODULE_STATE_LIVE;
> +	ret = !mod || mod->state == MODULE_STATE_LIVE
> +		|| mod->state == MODULE_STATE_GOING;
>  	mutex_unlock(&module_mutex);
>  
>  	return ret;
> @@ -2566,7 +2567,8 @@ static int add_unformed_module(struct module *mod)
>  	mutex_lock(&module_mutex);
>  	old = find_module_all(mod->name, strlen(mod->name), true);
>  	if (old != NULL) {
> -		if (old->state != MODULE_STATE_LIVE) {
> +		if (old->state == MODULE_STATE_COMING
> +		    || old->state == MODULE_STATE_UNFORMED) {
>  			/* Wait in case it fails to load. */
>  			mutex_unlock(&module_mutex);
>  			err = wait_event_interruptible(module_wq,
> @@ -2575,7 +2577,7 @@ static int add_unformed_module(struct module *mod)
>  				goto out_unlocked;
>  			goto again;
>  		}
> -		err = -EEXIST;
> +		err = old->state != MODULE_STATE_LIVE ? -EBUSY : -EEXIST;
>  		goto out;
>  	}
>  	mod_update_bounds(mod);


Prarit, can you verify this still does not break the issue you reported?
David, does this also fix your issue?

Petr, does this solve *any* of your issues? Can you also send a proper
patch with a commit log once we get confirmation of the tests.

I've been nose diving onto all of these 3 issues now and I have some
ideas of how to split this crap better and save even more memory on
bootup due to these stupid multiple requests. I want to first solve this
regression.

  Luis