[PATCH 30/31] Fix use of uninitialized variable in cache_grow()

[Suresh Jayaraman]

From: Miklos Szeredi <mszeredi@xxxxxxx>

This fixes a bug in reserve-slub.patch.

If cache_grow() was called with objp != NULL then the 'reserve' local
variable wasn't initialized. This resulted in ac->reserve being set to
a rubbish value.  Due to this in some circumstances huge amounts of
slab pages were allocated (due to slab_force_alloc() returning true),
which caused atomic page allocation failures and slowdown of the
system.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Suresh Jayaraman <sjayaraman@xxxxxxx>
---
 mm/slab.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

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. */
--
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