Re: [Bug #13319] Page allocation failures with b43 and p54usb

David Rientjes
2009-06-30T21:15:41Z

On Tue, 30 Jun 2009, Christoph Lameter wrote:

> > diff --git a/mm/slub.c b/mm/slub.c
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -142,6 +142,11 @@
> > SLAB_POISON | SLAB_STORE_USER)
> >
> > /*
> > + * The maximum amount of metadata added to a slab when debugging is enabled.
> > + */
> > +#define MAX_DEBUG_SIZE (3 * sizeof(void *) + 2 * sizeof(struct track))
> > +
> > +/*
> > * Set of flags that will prevent slab merging
> > */
> > #define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
> > @@ -1561,6 +1566,21 @@ slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
> > "default order: %d, min order: %d\n", s->name, s->objsize,
> > s->size, oo_order(s->oo), oo_order(s->min));
> >
> > + if (s->flags & (SLAB_POISON | SLAB_RED_ZONE | SLAB_STORE_USER)) {
> > + int min_order;
> > +
> > + /*
> > + * Debugging is enabled, which may increase oo_order(s->min), so
> > + * warn the user that allocation failures may be avoided if
> > + * debugging is enabled for this cache.
> > + */
> > + min_order = get_order(s->size - MAX_DEBUG_SIZE);
> > + if (min_order < oo_order(s->min))
> > + printk(KERN_WARNING " %s debugging increased min order "
> > + "from %d to %d, use slab_debug=-,%s to disable.",
> > + s->name, min_order, oo_order(s->min), s->name);
>
> It may be easier to check the order of the initial size vs. the order of
> the size with all metadata
>
> if (get_order(s->size) > get_order(s->objsize)
>

Ah, right. Then we could simply eliminate the check on s->flags to begin
with.

This patch is supposing that `slab_debug=-,<cache>' actually disables all
debugging for <cache> which would need to be implemented first, but I
think this is a better alternative than requiring slab_debug=A for full
debugging after enabling CONFIG_SLUB_DEBUG_ON.