On Fri, 8 Apr 2011, Dave Hansen wrote:
>
> I was tracking down a page allocation failure that ended up in vmalloc().
> Since vmalloc() uses 0-order pages, if somebody asks for an insane amount
> of memory, we'll still get a warning with "order:0" in it. That's not
> very useful.
>
> During recovery, vmalloc() also nicely frees all of the memory that it
> got up to the point of the failure. That is wonderful, but it also
> quickly hides any issues. We have a much different sitation if vmalloc()
> repeatedly fails 10GB in to:
>
> vmalloc(100 * 1<<30);
>
> versus repeatedly failing 4096 bytes in to a:
>
> vmalloc(8192);
>
> This patch will print out messages that look like this:
>
> [ 30.040774] bash: vmalloc failure allocating after 0 / 73728 bytes
>
Either the changelog or the patch is still wrong because the format of
this string is inconsistent.
> As a side issue, I also noticed that ctl_ioctl() does vmalloc() based
> solely on an unverified value passed in from userspace. Granted, it's
> under CAP_SYS_ADMIN, but it still frightens me a bit.
>
> Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
> ---
>
> linux-2.6.git-dave/mm/vmalloc.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff -puN mm/vmalloc.c~vmalloc-warn mm/vmalloc.c
> --- linux-2.6.git/mm/vmalloc.c~vmalloc-warn 2011-04-08 09:36:05.877020199 -0700
> +++ linux-2.6.git-dave/mm/vmalloc.c 2011-04-08 09:38:00.373093593 -0700
> @@ -1534,6 +1534,7 @@ static void *__vmalloc_node(unsigned lon
> static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> pgprot_t prot, int node, void *caller)
> {
> + int order = 0;
Unnecessary, we can continue to hardcode the 0, vmalloc isn't going to use
higher order allocs (it's there to avoid such things!).
> struct page **pages;
> unsigned int nr_pages, array_size, i;
> gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
> @@ -1560,11 +1561,12 @@ static void *__vmalloc_area_node(struct
>
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page;
> + gfp_t tmp_mask = gfp_mask | __GFP_NOWARN;
I think it would be better to just do away with this as well and just
hardwire the __GFP_NOWARN directly into the two allocation calls.
>
> if (node < 0)
> - page = alloc_page(gfp_mask);
> + page = alloc_page(tmp_mask);
> else
> - page = alloc_pages_node(node, gfp_mask, 0);
> + page = alloc_pages_node(node, tmp_mask, order);
>
> if (unlikely(!page)) {
> /* Successfully allocated i pages, free them in __vunmap() */
> @@ -1579,6 +1581,9 @@ static void *__vmalloc_area_node(struct
> return area->addr;
>
> fail:
> + nopage_warning(gfp_mask, order, "vmalloc: allocation failure, "
> + "allocated %ld of %ld bytes\n",
> + (area->nr_pages*PAGE_SIZE), area->size);
> vfree(area->addr);
> return NULL;
> }
--
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