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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, cai@lca.pw, catalin.marinas@arm.com,
	linux-mm@kvack.org, mm-commits@vger.kernel.org,
	torvalds@linux-foundation.org, vitaly.wool@konsulko.com
Subject: [patch 1/5] mm/z3fold: silence kmemleak false positives of slots
Date: Wed, 27 May 2020 22:20:40 -0700	[thread overview]
Message-ID: <20200528052040.tET7TeyHc%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200527222015.62ba8592af63dae12ab58ffe@linux-foundation.org>

From: Qian Cai <cai@lca.pw>
Subject: mm/z3fold: silence kmemleak false positives of slots

Kmemleak reported many leaks while under memory pressue in,

slots = alloc_slots(pool, gfp);

which is referenced by "zhdr" in init_z3fold_page(),

zhdr->slots = slots;

However, "zhdr" could be gone without freeing slots as the later will be
freed separately when the last "handle" off of "handles" array is freed. It
will be within "slots" which is always aligned.

unreferenced object 0xc000000fdadc1040 (size 104):
  comm "oom04", pid 140476, jiffies 4295359280 (age 3454.970s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000d1f0f5eb>] z3fold_zpool_malloc+0x7b0/0xe10
    alloc_slots at mm/z3fold.c:214
    (inlined by) init_z3fold_page at mm/z3fold.c:412
    (inlined by) z3fold_alloc at mm/z3fold.c:1161
    (inlined by) z3fold_zpool_malloc at mm/z3fold.c:1735
    [<0000000064a2e969>] zpool_malloc+0x34/0x50
    [<00000000af63e491>] zswap_frontswap_store+0x60c/0xda0
    zswap_frontswap_store at mm/zswap.c:1093
    [<00000000af5e07e0>] __frontswap_store+0x128/0x330
    [<00000000de2f582b>] swap_writepage+0x58/0x110
    [<000000000120885f>] pageout+0x16c/0xa40
    [<00000000444c1f68>] shrink_page_list+0x1ac8/0x25c0
    [<00000000d19e8610>] shrink_inactive_list+0x270/0x730
    [<00000000e17df726>] shrink_lruvec+0x444/0xf30
    [<000000005f02ab35>] shrink_node+0x2a4/0x9c0
    [<00000000014cabbd>] do_try_to_free_pages+0x158/0x640
    [<00000000dcfaba07>] try_to_free_pages+0x1bc/0x5f0
    [<00000000fa207ab8>] __alloc_pages_slowpath.constprop.60+0x4dc/0x15a0
    [<000000003669f1d2>] __alloc_pages_nodemask+0x520/0x650
    [<0000000011fa4168>] alloc_pages_vma+0xc0/0x420
    [<0000000098b376f2>] handle_mm_fault+0x1174/0x1bf0

Link: http://lkml.kernel.org/r/20200522220052.2225-1-cai@lca.pw
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Vitaly Wool <vitaly.wool@konsulko.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/z3fold.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/z3fold.c~mm-z3fold-silence-kmemleak-false-positives-of-slots
+++ a/mm/z3fold.c
@@ -43,6 +43,7 @@
 #include <linux/spinlock.h>
 #include <linux/zpool.h>
 #include <linux/magic.h>
+#include <linux/kmemleak.h>
 
 /*
  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
@@ -215,6 +216,8 @@ static inline struct z3fold_buddy_slots
 				 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
 
 	if (slots) {
+		/* It will be freed separately in free_handle(). */
+		kmemleak_not_leak(slots);
 		memset(slots->slot, 0, sizeof(slots->slot));
 		slots->pool = (unsigned long)pool;
 		rwlock_init(&slots->lock);
_


  reply	other threads:[~2020-05-28  5:20 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-28  5:20 incoming Andrew Morton
2020-05-28  5:20 ` Andrew Morton [this message]
2020-05-28  5:20 ` [patch 2/5] mm,thp: stop leaking unreleased file pages Andrew Morton
2020-05-28  5:20 ` [patch 3/5] mm: remove VM_BUG_ON(PageSlab()) from page_mapcount() Andrew Morton
2020-05-28  5:20 ` [patch 4/5] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info() Andrew Morton
2020-05-28  5:20 ` [patch 5/5] include/asm-generic/topology.h: guard cpumask_of_node() macro argument Andrew Morton
2020-05-28 20:10 ` incoming Linus Torvalds
2020-05-29 20:31   ` incoming Andrew Morton
2020-05-29 20:38     ` incoming Linus Torvalds
2020-05-29 21:12       ` incoming Andrew Morton
2020-05-29 21:20         ` incoming Linus Torvalds

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