linux-kernel - [PATCH v1] mm:free unused pages in kmalloc

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Message-ID: <20200627045507.GA57675@lilong>
Date:   Sat, 27 Jun 2020 04:55:07 +0000
From:   Long Li <lonuxli.64@...il.com>
To:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] mm:free unused pages in kmalloc_order

Environment using the slub allocator, 1G memory in my ARM32.
kmalloc(1024, GFP_HIGHUSER) can allocate memory normally,
kmalloc(64*1024, GFP_HIGHUSER) will cause a memory leak, because
alloc_pages returns highmem physical pages, but it cannot be directly
converted into a virtual address and return NULL, the pages has not
been released. Usually driver developers will not use the
GFP_HIGHUSER flag to allocate memory in kmalloc, but I think this
memory leak is not perfect, it is best to be fixed. This is the
first time I have posted a patch, there may be something wrong.

Signed-off-by: Long Li <lonuxli.64@...il.com>
---
 mm/slab_common.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index a143a8c8f874..d2c53b980ab3 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -819,8 +819,12 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 	page = alloc_pages(flags, order);
 	if (likely(page)) {
 		ret = page_address(page);
-		mod_node_page_state(page_pgdat(page), NR_SLAB_UNRECLAIMABLE_B,
-				    PAGE_SIZE << order);
+		if (ret)
+			mod_node_page_state(page_pgdat(page),
+					NR_SLAB_UNRECLAIMABLE_B,
+					PAGE_SIZE << order);
+		else
+			__free_pages(page, order);
 	}
 	ret = kasan_kmalloc_large(ret, size, flags);
 	/* As ret might get tagged, call kmemleak hook after KASAN. */
-- 
2.17.1