Messages in this thread Patch in this message | | | From | Jesper Juhl <> | Subject | Re: [PATCH] fix memory leak in mm/slab.c::alloc_kmemlist() (try #3) | Date | Wed, 22 Mar 2006 01:54:16 +0100 |
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Hi Pekka, Andrew, Christoph & everyone else,
On Monday 20 March 2006 09:55, Jesper Juhl wrote: > Hi Pekka, > > On 3/19/06, Pekka Enberg <penberg@cs.helsinki.fi> wrote: > > On 3/18/06, Jesper Juhl <jesper.juhl@gmail.com> wrote: > > > Currently the only caller of alloc_kmemlist() will BUG() if alloc_kmemlist() > > > fails, but that doesn't mean we shouldn't clean up properly IMHO. Also, the > > > caller (do_tune_cpucache()) could maybe be changed in the future to do > > > something more clever than just BUG() and in that case we really shouldn't > > > be leaking memory when we return -ENOMEM. > > > > Yeah, and BUG() can be no-op for embedded. > > > > On 3/18/06, Jesper Juhl <jesper.juhl@gmail.com> wrote: > > > The patch has been compile and boot tested on x86, but since I'm not very > > > intimate with the slab code I'd appreciate it if someone would take a close > > > look on the changes before merging them. > > > > You probably didn't hit the error path on your x86 box. The patch > > looks good to me for -mm although there's few comments below. > > > > > +/* > > > + If one or more allocations fail we need to undo all allocations done up to > > > + this point. > > > + Unfortunately this means yet another loop, but since this only happens on > > > + failure and frees up memory in a memory-tight situation, it's not too bad. > > > + */ > > > > The formatting of this comment looks strange. > > > > > + for_each_online_node(node) { > > > + if (count <= 0) > > > + break; > > > + if (cachep->nodelists[node]) { > > > > Would probably make sense to extract the above expression into local > > variable to reduce kernel text size. > > > > > + kfree(cachep->nodelists[node]->shared); > > > + free_alien_cache(cachep->nodelists[node]->alien); > > > + kfree(cachep->nodelists[node]); > > > + cachep->nodelists[node] = NULL; > > > + } > > > + count--; > > > + } > > > + return -ENOMEM; > > > > Thank you very much for your feedback. > > I'll create an updated patch with the changes you suggest. They make > perfect sense. >
Here's the latest version of my patch to fix the mem leak in alloc_kmemlist(). It should address Pekkas's comments.
Andrew: Do you think this could go into -mm and get some field testing, so perhaps it has a chance of making 2.6.17?
Fix memory leak in mm/slab.c::alloc_kmemlist(). If one allocation fails we have to roll-back all allocations made up to the point of failure.
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com> ---
mm/slab.c | 36 ++++++++++++++++++++++++++++++------ 1 files changed, 30 insertions(+), 6 deletions(-)
--- linux-2.6.16-rc6-mm2-orig/mm/slab.c 2006-03-18 16:55:55.000000000 +0100 +++ linux-2.6.16-rc6-mm2/mm/slab.c 2006-03-21 22:33:45.000000000 +0100 @@ -3399,12 +3399,17 @@ EXPORT_SYMBOL_GPL(kmem_cache_name); static int alloc_kmemlist(struct kmem_cache *cachep) { int node; + int count = -1; struct kmem_list3 *l3; - int err = 0; + struct array_cache *new; + struct array_cache **new_alien; for_each_online_node(node) { - struct array_cache *nc = NULL, *new; - struct array_cache **new_alien = NULL; + struct array_cache *nc = NULL; + + new = NULL; + new_alien = NULL; + count++; #ifdef CONFIG_NUMA new_alien = alloc_alien_cache(node, cachep->limit); if (!new_alien) @@ -3447,10 +3452,29 @@ static int alloc_kmemlist(struct kmem_ca cachep->batchcount + cachep->num; cachep->nodelists[node] = l3; } - return err; + return 0; +/** + * If one or more allocations fail we need to undo all allocations done up to + * this point. Unfortunately this means yet another loop, but since this only + * happens on failure and frees up memory in a memory-tight situation, it's + * not too bad. + */ fail: - err = -ENOMEM; - return err; + kfree(new); + free_alien_cache(new_alien); + for_each_online_node(node) { + if (count <= 0) + break; + l3 = cachep->nodelists[node]; + if (l3) { + kfree(l3->shared); + free_alien_cache(l3->alien); + kfree(l3); + cachep->nodelists[node] = NULL; + } + count--; + } + return -ENOMEM; } struct ccupdate_struct {
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