Messages in this thread | | | Date | Fri, 2 Oct 2009 03:05:07 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH 30/31] Fix use of uninitialized variable in cache_grow() |
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On Fri, 2 Oct 2009, Neil Brown wrote:
> > > Index: mmotm/mm/slab.c > > > =================================================================== > > > --- mmotm.orig/mm/slab.c > > > +++ mmotm/mm/slab.c > > > @@ -2760,7 +2760,7 @@ static int cache_grow(struct kmem_cache > > > size_t offset; > > > gfp_t local_flags; > > > struct kmem_list3 *l3; > > > - int reserve; > > > + int reserve = -1; > > > > > > /* > > > * Be lazy and only check for valid flags here, keeping it out of the > > > @@ -2816,7 +2816,8 @@ static int cache_grow(struct kmem_cache > > > if (local_flags & __GFP_WAIT) > > > local_irq_disable(); > > > check_irq_off(); > > > - slab_set_reserve(cachep, reserve); > > > + if (reserve != -1) > > > + slab_set_reserve(cachep, reserve); > > > spin_lock(&l3->list_lock); > > > > > > /* Make slab active. */ > > > > Given the patch description, shouldn't this be a test for objp != NULL > > instead, then? > > In between those to patch hunks, cache_grow contains the code: > if (!objp) > objp = kmem_getpages(cachep, local_flags, nodeid, &reserve); > if (!objp) > goto failed; > > We can no longer test if objp was NULL on entry to the function. > We could take a copy of objp on entry to the function, and test it > here. But initialising 'reserve' to an invalid value is easier. >
Seems like you could do all this in kmem_getpages(), then, by calling slab_set_reserve(cachep, page->reserve) before returning the new page?
[ I'd also drop the branch in slab_set_reserve(), it's faster to just assign it unconditionally. ]
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