Re: [PATCH] kmalloc: Return NULL instead of link failure

From: Pekka Enberg
Date: Tue Jan 27 2009 - 16:54:11 EST

Andrew Morton wrote:
On Tue, 20 Jan 2009 10:53:26 -0500
Jeff Mahoney <jeffm@xxxxxxxx> wrote:

Hash: SHA1

The SLAB kmalloc with a constant value isn't consistent with the other
implementations because it bails out with __you_cannot_kmalloc_that_much
rather than returning NULL and properly allowing the caller to fall back
to vmalloc or take other action. This doesn't happen with a non-constant
value or with SLOB or SLUB.

Starting with 2.6.28, I've been seeing build failures on s390x. This is
due to init_section_page_cgroup trying to allocate 2.5MB when the max
size for a kmalloc on s390x is 2MB.

It's failing because the value is constant. The workarounds at the call
size are ugly and the caller shouldn't have to change behavior depending
on what the backend of the API is.

So, this patch eliminates the link failure and returns NULL like the
other implementations.

OK by me, is that's what the other sl[]b.c implementations

That __you_cannot_kmalloc_that_much() thing has frequently been a PITA
anyway - some gcc versions flub the constant_p() test and end up
referencing __you_cannot_kmalloc_that_much() when the callsite was
passing a variable `size' arg.


Strange patch format, but it applied.

I'll punt this patch in the Pekka direction.

Applied, thanks!

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at