[PATCH] module: avoid call vmalloc if init size is zero

[PATCH] module: avoid call vmalloc if init size is zero

[Dmitry Antipov]

For the architectures with it's own module_alloc(), if module init
size is zero, avoiding module_alloc_update_bounds() and memset()
no-op calls also eliminates warn_alloc_failed() zero-size warning
in __vmalloc_node_range().

Signed-off-by: Dmitry Antipov <dmitry.antipov@linaro.org>
---
 kernel/module.c |   31 +++++++++++++++++--------------
 1 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 2c93276..bbe1c5b 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2644,20 +2644,23 @@ static int move_module(struct module *mod, struct load_info *info)
 	memset(ptr, 0, mod->core_size);
 	mod->module_core = ptr;
 
-	ptr = module_alloc_update_bounds(mod->init_size);
-	/*
-	 * The pointer to this block is stored in the module structure
-	 * which is inside the block. This block doesn't need to be
-	 * scanned as it contains data and code that will be freed
-	 * after the module is initialized.
-	 */
-	kmemleak_ignore(ptr);
-	if (!ptr && mod->init_size) {
-		module_free(mod, mod->module_core);
-		return -ENOMEM;
-	}
-	memset(ptr, 0, mod->init_size);
-	mod->module_init = ptr;
+	if (mod->init_size) {
+		ptr = module_alloc_update_bounds(mod->init_size);
+		/*
+		 * The pointer to this block is stored in the module structure
+		 * which is inside the block. This block doesn't need to be
+		 * scanned as it contains data and code that will be freed
+		 * after the module is initialized.
+		 */
+		kmemleak_ignore(ptr);
+		if (!ptr) {
+			module_free(mod, mod->module_core);
+			return -ENOMEM;
+		}
+		memset(ptr, 0, mod->init_size);
+		mod->module_init = ptr;
+	} else
+		mod->module_init = NULL;
 
 	/* Transfer each section which specifies SHF_ALLOC */
 	pr_debug("final section addresses:\n");
-- 
1.7.7.5

Re: [PATCH] module: avoid call vmalloc if init size is zero

[Rusty Russell]

On Fri, 27 Jan 2012 11:19:16 +0400, Dmitry Antipov <dmitry.antipov@linaro.org> wrote:
> For the architectures with it's own module_alloc(), if module init
> size is zero, avoiding module_alloc_update_bounds() and memset()
> no-op calls also eliminates warn_alloc_failed() zero-size warning
> in __vmalloc_node_range().
> 
> Signed-off-by: Dmitry Antipov <dmitry.antipov@linaro.org>

Please fix __vmalloc_node_range() instead to return ZERO_SIZE_PTR.
And of course, vfree() to use ZERO_OR_NULL_PTR().

Thanks,
Rusty.

Re: [PATCH] module: avoid call vmalloc if init size is zero

[Dmitry Antipov]

On 01/27/2012 03:21 PM, Rusty Russell wrote:

> Please fix __vmalloc_node_range() instead to return ZERO_SIZE_PTR.
> And of course, vfree() to use ZERO_OR_NULL_PTR().

For the convenience and uniformity, should {alloc,free}_percpu() be
also modified in that way?

Dmitry

Re: [PATCH] module: avoid call vmalloc if init size is zero

[Rusty Russell]

On Mon, 30 Jan 2012 11:28:12 +0400, Dmitry Antipov <dmitry.antipov@linaro.org> wrote:
> On 01/27/2012 03:21 PM, Rusty Russell wrote:
> 
> > Please fix __vmalloc_node_range() instead to return ZERO_SIZE_PTR.
> > And of course, vfree() to use ZERO_OR_NULL_PTR().
> 
> For the convenience and uniformity, should {alloc,free}_percpu() be
> also modified in that way?

Yep!

Thanks,
Rusty.