[patch 079/134] z3fold: fix memory leak in kmem cache

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From: Vitaly Wool <vitalywool@xxxxxxxxx>
Subject: z3fold: fix memory leak in kmem cache

Currently there is a leak in init_z3fold_page() -- it allocates handles
from kmem cache even for headless pages, but then they are never used and
never freed, so eventually kmem cache may get exhausted.  This patch
provides a fix for that.

Link: http://lkml.kernel.org/r/20190917185352.44cf285d3ebd9e64548de5de@xxxxxxxxx
Signed-off-by: Vitaly Wool <vitalywool@xxxxxxxxx>
Reported-by: Markus Linnala <markus.linnala@xxxxxxxxx>
Tested-by: Markus Linnala <markus.linnala@xxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Henry Burns <henrywolfeburns@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/z3fold.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/mm/z3fold.c~z3fold-fix-memory-leak-in-kmem-cache
+++ a/mm/z3fold.c
@@ -295,14 +295,11 @@ static void z3fold_unregister_migration(
  }
 
 /* Initializes the z3fold header of a newly allocated z3fold page */
-static struct z3fold_header *init_z3fold_page(struct page *page,
+static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
 					struct z3fold_pool *pool, gfp_t gfp)
 {
 	struct z3fold_header *zhdr = page_address(page);
-	struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
-
-	if (!slots)
-		return NULL;
+	struct z3fold_buddy_slots *slots;
 
 	INIT_LIST_HEAD(&page->lru);
 	clear_bit(PAGE_HEADLESS, &page->private);
@@ -310,6 +307,12 @@ static struct z3fold_header *init_z3fold
 	clear_bit(NEEDS_COMPACTING, &page->private);
 	clear_bit(PAGE_STALE, &page->private);
 	clear_bit(PAGE_CLAIMED, &page->private);
+	if (headless)
+		return zhdr;
+
+	slots = alloc_slots(pool, gfp);
+	if (!slots)
+		return NULL;
 
 	spin_lock_init(&zhdr->page_lock);
 	kref_init(&zhdr->refcount);
@@ -930,7 +933,7 @@ retry:
 	if (!page)
 		return -ENOMEM;
 
-	zhdr = init_z3fold_page(page, pool, gfp);
+	zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
 	if (!zhdr) {
 		__free_page(page);
 		return -ENOMEM;
_



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