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Commit 8d8022e8 authored by Rusty Russell's avatar Rusty Russell
Browse files

module: do percpu allocation after uniqueness check. No, really! 



v3.8-rc1-5-g1fb9341 was supposed to stop parallel kvm loads exhausting
percpu memory on large machines:

    Now we have a new state MODULE_STATE_UNFORMED, we can insert the
    module into the list (and thus guarantee its uniqueness) before we
    allocate the per-cpu region.

In my defence, it didn't actually say the patch did this.  Just that
we "can".

This patch actually *does* it.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Tested-by: default avatarJim Hull <jim.hull@hp.com>
Cc: stable@kernel.org # 3.8
parent 54041d8a

kernel/module.c

+18 −16
Original line number Diff line number Diff line
@@ -2940,7 +2940,6 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) 
{

	/* Module within temporary copy. */

	struct module *mod;

	Elf_Shdr *pcpusec;

	int err;



	mod = setup_load_info(info, flags);
@@ -2955,17 +2954,10 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) 
	err = module_frob_arch_sections(info->hdr, info->sechdrs,

					info->secstrings, mod);

	if (err < 0)

		goto out;

		return ERR_PTR(err);



	pcpusec = &info->sechdrs[info->index.pcpu];

	if (pcpusec->sh_size) {

		/* We have a special allocation for this section. */

		err = percpu_modalloc(mod,

				      pcpusec->sh_size, pcpusec->sh_addralign);

		if (err)

			goto out;

		pcpusec->sh_flags &= ~(unsigned long)SHF_ALLOC;

	}

	/* We will do a special allocation for per-cpu sections later. */

	info->sechdrs[info->index.pcpu].sh_flags &= ~(unsigned long)SHF_ALLOC;



	/* Determine total sizes, and put offsets in sh_entsize.  For now

	   this is done generically; there doesn't appear to be any
@@ -2976,17 +2968,22 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) 
	/* Allocate and move to the final place */

	err = move_module(mod, info);

	if (err)

		goto free_percpu;

		return ERR_PTR(err);



	/* Module has been copied to its final place now: return it. */

	mod = (void *)info->sechdrs[info->index.mod].sh_addr;

	kmemleak_load_module(mod, info);

	return mod;

}



free_percpu:

	percpu_modfree(mod);

out:

	return ERR_PTR(err);

static int alloc_module_percpu(struct module *mod, struct load_info *info)

{

	Elf_Shdr *pcpusec = &info->sechdrs[info->index.pcpu];

	if (!pcpusec->sh_size)

		return 0;



	/* We have a special allocation for this section. */

	return percpu_modalloc(mod, pcpusec->sh_size, pcpusec->sh_addralign);

}



/* mod is no longer valid after this! */
@@ -3262,6 +3259,11 @@ static int load_module(struct load_info *info, const char __user *uargs, 
	}

#endif



	/* To avoid stressing percpu allocator, do this once we're unique. */

	err = alloc_module_percpu(mod, info);

	if (err)

		goto unlink_mod;



	/* Now module is in final location, initialize linked lists, etc. */

	err = module_unload_init(mod);

	if (err)