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>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4581ddcdda500deffa0076c56c310ae093fabad3..b5ccf3158d82440525eecceb66e0f291e7cd2795 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -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;
 }