Commit 22943ab1 authored May 24, 2011 by Dave Hansen Committed by Linus Torvalds May 25, 2011

mm: print vmalloc() state after allocation failures



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:

[   68.123503] vmalloc: allocation failure, allocated 6680576 of 13426688 bytes
[   68.124218] bash: page allocation failure: order:0, mode:0xd2
[   68.124811] Pid: 3770, comm: bash Not tainted 2.6.39-rc3-00082-g85f2e68-dirty #333
[   68.125579] Call Trace:
[   68.125853]  [<ffffffff810f6da6>] warn_alloc_failed+0x146/0x170
[   68.126464]  [<ffffffff8107e05c>] ? printk+0x6c/0x70
[   68.126791]  [<ffffffff8112b5d4>] ? alloc_pages_current+0x94/0xe0
[   68.127661]  [<ffffffff8111ed37>] __vmalloc_node_range+0x237/0x290
...

The 'order' variable is added for clarity when calling warn_alloc_failed()
to avoid having an unexplained '0' as an argument.

The 'tmp_mask' is because adding an open-coded '| __GFP_NOWARN' would take
us over 80 columns for the alloc_pages_node() call.  If we are going to
add a line, it might as well be one that makes the sucker easier to read.

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@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a238ab5b

mm/vmalloc.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1534,6 +1534,7 @@ static void *__vmalloc_node(unsigned long size, unsigned long align,
		static void __vmalloc_area_node(struct vm_struct area, gfp_t gfp_mask,
		pgprot_t prot, int node, void *caller)
		{
		const int order = 0;
		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 vm_struct area, gfp_t gfp_mask,

		for (i = 0; i < area->nr_pages; i++) {
		struct page *page;
		gfp_t tmp_mask = gfp_mask \| __GFP_NOWARN;

		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 vm_struct area, gfp_t gfp_mask,
		return area->addr;

		fail:
		warn_alloc_failed(gfp_mask, order, "vmalloc: allocation failure, "
		"allocated %ld of %ld bytes\n",
		(area->nr_pages*PAGE_SIZE), area->size);
		vfree(area->addr);
		return NULL;
		}

Admin message