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Date: Fri, 28 Aug 2020 13:39:21 +0200
From: SeongJae Park <sjpark@...zon.com>
To: Alkaid <zgf574564920@...il.com>
CC: <akpm@...ux-foundation.org>, SeongJae Park <sjpark@...zon.de>,
<Jonathan.Cameron@...wei.com>, <aarcange@...hat.com>,
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<snu@...zon.de>, <vbabka@...e.cz>, <vdavydov.dev@...il.com>,
<yang.shi@...ux.alibaba.com>, <ying.huang@...el.com>,
<linux-damon@...zon.com>, <linux-mm@...ck.org>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
SeongJae Park <sjpark@...zon.com>
Subject: Re: [RFC v7 06/10] mm/damon: Implement callbacks for physical memory monitoring
On Fri, 28 Aug 2020 11:53:15 +0200 SeongJae Park <sjpark@...zon.com> wrote:
> On Fri, 28 Aug 2020 04:11:56 -0400 Alkaid <zgf574564920@...il.com> wrote:
>
> >
> > [-- Attachment #1: Type: text/plain, Size: 2677 bytes --]
> >
> > Hi SeongJae,
> >
> > I think there are potential memory leaks in the following execution paths
>
> Agreed, definitely memory leaks exists. Thank you for let me know this! I
> will post a patch for this soon.
And, below is the patch. The complete tree is available at:
https://github.com/sjp38/linux/tree/damon/next
Thanks,
SeongJae Park
==================================== >8 =======================================
>From 8f605d807c55b536ab5b0f87306ac78033dc4499 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sjpark@...zon.de>
Date: Fri, 28 Aug 2020 11:29:30 +0000
Subject: [PATCH] mm/damon/paddr: Add missed 'put_page()' calls
Exceptional cases handlings in 'damon_phys_mkold()' and
'damon_phys_young()' doesn't properly put pages. This commit fixes the
problem by adding the 'put_page()' call.
Reported-by: Alkaid <zgf574564920@...il.com>
Signed-off-by: SeongJae Park <sjpark@...zon.de>
---
mm/damon.c | 53 ++++++++++++++++++++++++++++-------------------------
1 file changed, 28 insertions(+), 25 deletions(-)
diff --git a/mm/damon.c b/mm/damon.c
index d0d55656553b..74a10ea54958 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -836,12 +836,16 @@ unsigned int kdamond_check_vm_accesses(struct damon_ctx *ctx)
/* access check functions for physical address based regions */
/*
- * Get a page by pfn if it is in the LRU list. Otherwise, returns NULL.
+ * Get a page by @pfn if it is in the LRU list and mapped. If the page needs
+ * locked, do the lock and save the result in @locked. Otherwise, returns
+ * NULL.
*
- * The body of this function is stollen from the 'page_idle_get_page()'. We
- * steal rather than reuse it because the code is quite simple .
+ * The body of this function is mostly stollen from the 'page_idle_get_page()'
+ * and 'page_idle_clear_pte_refs()'. We steal rather than reuse it not because
+ * we are great artists but the code is quite simple and we need to unify parts
+ * of the two functions.
*/
-static struct page *damon_phys_get_page(unsigned long pfn)
+static struct page *damon_phys_get_page(unsigned long pfn, bool *locked)
{
struct page *page = pfn_to_online_page(pfn);
pg_data_t *pgdat;
@@ -854,9 +858,22 @@ static struct page *damon_phys_get_page(unsigned long pfn)
spin_lock_irq(&pgdat->lru_lock);
if (unlikely(!PageLRU(page))) {
put_page(page);
- page = NULL;
+ spin_unlock_irq(&pgdat->lru_lock);
+ return NULL;
}
spin_unlock_irq(&pgdat->lru_lock);
+
+ if (!page_mapped(page) || !page_rmapping(page)) {
+ put_page(page);
+ return NULL;
+ }
+
+ *locked = !PageAnon(page) || PageKsm(page);
+ if (*locked && !trylock_page(page)) {
+ put_page(page);
+ return NULL;
+ }
+
return page;
}
@@ -869,26 +886,19 @@ static bool damon_page_mkold(struct page *page, struct vm_area_struct *vma,
static void damon_phys_mkold(unsigned long paddr)
{
- struct page *page = damon_phys_get_page(PHYS_PFN(paddr));
+ bool locked;
+ struct page *page = damon_phys_get_page(PHYS_PFN(paddr), &locked);
struct rmap_walk_control rwc = {
.rmap_one = damon_page_mkold,
.anon_lock = page_lock_anon_vma_read,
};
- bool need_lock;
if (!page)
return;
- if (!page_mapped(page) || !page_rmapping(page))
- return;
-
- need_lock = !PageAnon(page) || PageKsm(page);
- if (need_lock && !trylock_page(page))
- return;
-
rmap_walk(page, &rwc);
- if (need_lock)
+ if (locked)
unlock_page(page);
put_page(page);
}
@@ -930,7 +940,8 @@ static bool damon_page_accessed(struct page *page, struct vm_area_struct *vma,
static bool damon_phys_young(unsigned long paddr, unsigned long *page_sz)
{
- struct page *page = damon_phys_get_page(PHYS_PFN(paddr));
+ bool locked;
+ struct page *page = damon_phys_get_page(PHYS_PFN(paddr), &locked);
struct damon_phys_access_chk_result result = {
.page_sz = PAGE_SIZE,
.accessed = false,
@@ -940,21 +951,13 @@ static bool damon_phys_young(unsigned long paddr, unsigned long *page_sz)
.rmap_one = damon_page_accessed,
.anon_lock = page_lock_anon_vma_read,
};
- bool need_lock;
if (!page)
return false;
- if (!page_mapped(page) || !page_rmapping(page))
- return false;
-
- need_lock = !PageAnon(page) || PageKsm(page);
- if (need_lock && !trylock_page(page))
- return false;
-
rmap_walk(page, &rwc);
- if (need_lock)
+ if (locked)
unlock_page(page);
put_page(page);
--
2.17.1
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