Messages in this thread | | | Date | Mon, 14 Nov 2022 16:45:05 +0100 | From | David Hildenbrand <> | Subject | Re: [PATCH v2 2/2] module: Merge same-name module load requests |
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On 14.11.22 16:38, Luis Chamberlain wrote: > On Mon, Nov 14, 2022 at 09:57:56AM +0100, David Hildenbrand wrote: >> On 12.11.22 02:47, Luis Chamberlain wrote: >>> 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? >> >> I didn't try, but from a quick glimpse I assume no. Allocating module space >> happens before handling eventual duplicates right now, before a module even >> is "alive" and in the MODULE_STATE_UNFORMED state. > > The first two hunks are a revert of commit 6e6de3dee51a and I'm under > the impression that cauased your issues as *more* modules states are > allowed through. > > The last hunk tries to fix what 6e6de3dee51a wanted to do. >
Note that I don't think the issue I raised is due to 6e6de3dee51a.
>> But maybe I am missing something important. > > Please do test if you can.
I don't have the machine at hand right now. But, again, I doubt this will fix it.
The flow is in load_module():
mod = layout_and_allocate(info, flags); if (IS_ERR(mod)) { ... }
audit_log_kern_module(mod->name);
/* Reserve our place in the list. */ err = add_unformed_module(mod); if (err) goto free_module;
You can have 400 threads in layout_and_allocate() loading the same module at the same time and running out of module space. Any changes to add_unformed_module() and finished_loading() won't change that, because they are not involved before the module space allocations happened.
-- Thanks,
David / dhildenb
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