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SubjectRe: 2.6.0-test5/6 (and probably 7 too) size-4096 memory leak
Andrew Morton wrote:

>I'm thinking we need to stuff builtin_return_address(0) into the object and
>write a dumper, but I haven't looked into that. Maybe I can persuade
>Manfred to cook up a custom patch to do that? Just for size-4096? Something
>really crude will be fine.
>
>
I've attached something: with the patch applied, `echo "size-4096 0 0 0"
> /proc/slabinfo` dumps all caller addresses.

It works fine and dumps all 25 outstanding objects of my bochs setup -
you might have to limit the dumps if you have 100k objects.

--
Manfred
--- 2.6/mm/slab.c 2003-10-09 21:23:19.000000000 +0200
+++ build-2.6/mm/slab.c 2003-10-16 07:32:06.000000000 +0200
@@ -1891,6 +1891,15 @@
*dbg_redzone1(cachep, objp) = RED_ACTIVE;
*dbg_redzone2(cachep, objp) = RED_ACTIVE;
}
+ {
+ int objnr;
+ struct slab *slabp;
+
+ slabp = GET_PAGE_SLAB(virt_to_page(objp));
+
+ objnr = (objp - slabp->s_mem) / cachep->objsize;
+ slab_bufctl(slabp)[objnr] = (int)caller;
+ }
objp += obj_dbghead(cachep);
if (cachep->ctor && cachep->flags & SLAB_POISON) {
unsigned long ctor_flags = SLAB_CTOR_CONSTRUCTOR;
@@ -1952,12 +1961,14 @@
objnr = (objp - slabp->s_mem) / cachep->objsize;
check_slabp(cachep, slabp);
#if DEBUG
+#if 0
if (slab_bufctl(slabp)[objnr] != BUFCTL_FREE) {
printk(KERN_ERR "slab: double free detected in cache '%s', objp %p.\n",
cachep->name, objp);
BUG();
}
#endif
+#endif
slab_bufctl(slabp)[objnr] = slabp->free;
slabp->free = objnr;
STATS_DEC_ACTIVE(cachep);
@@ -2694,6 +2705,22 @@
.show = s_show,
};

+static void do_dump_slabp(kmem_cache_t *cachep)
+{
+ struct list_head *q;
+
+ check_irq_on();
+ spin_lock_irq(&cachep->spinlock);
+ list_for_each(q,&cachep->lists.slabs_full) {
+ struct slab *slabp;
+ int i;
+ slabp = list_entry(q, struct slab, list);
+ for (i=0;i<cachep->num;i++)
+ printk(KERN_DEBUG "obj %p/%d: %p\n", slabp, i, (void*)(slab_bufctl(slabp)[i]));
+ }
+ spin_unlock_irq(&cachep->spinlock);
+}
+
#define MAX_SLABINFO_WRITE 128
/**
* slabinfo_write - Tuning for the slab allocator
@@ -2734,6 +2761,7 @@
batchcount < 1 ||
batchcount > limit ||
shared < 0) {
+ do_dump_slabp(cachep);
res = -EINVAL;
} else {
res = do_tune_cpucache(cachep, limit, batchcount, shared);
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