linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Mel Gorman <mgorman@techsingularity.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Colin Ian King <colin.king@canonical.com>
Subject: [PATCH] mm/page_alloc: Add a bulk page allocator -fix -fix
Date: Tue, 30 Mar 2021 12:48:47 +0100	[thread overview]
Message-ID: <20210330114847.GX3697@techsingularity.net> (raw)

Colin Ian King reported the following problem (slightly edited)

	Author: Mel Gorman <mgorman@techsingularity.net>
	Date:   Mon Mar 29 11:12:24 2021 +1100

	    mm/page_alloc: add a bulk page allocator

	...

	Static analysis on linux-next with Coverity has found a potential
	uninitialized variable issue in function __alloc_pages_bulk with
	the following commit:

	...

	    Uninitialized scalar variable (UNINIT)
	    15. uninit_use_in_call: Using uninitialized value alloc_flags when
	        calling prepare_alloc_pages.

	5056        if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask,
						&ac, &alloc_gfp, &alloc_flags))

The problem is that prepare_alloc_flags only updates alloc_flags
which must have a valid initial value. The appropriate initial value is
ALLOC_WMARK_LOW to avoid the bulk allocator pushing a zone below the low
watermark without waking kswapd assuming the GFP mask allows kswapd to
be woken.

This is a second fix to the mmotm patch
mm-page_alloc-add-a-bulk-page-allocator.patch . It will cause a mild conflict
with a later patch due to renaming of an adjacent variable that is trivially
resolved. I can post a full series with the fixes merged if that is preferred.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 92d55f80c289..dabef0b910c9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4990,7 +4990,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 	struct list_head *pcp_list;
 	struct alloc_context ac;
 	gfp_t alloc_gfp;
-	unsigned int alloc_flags;
+	unsigned int alloc_flags = ALLOC_WMARK_LOW;
 	int allocated = 0;
 
 	if (WARN_ON_ONCE(nr_pages <= 0))

             reply	other threads:[~2021-03-30 11:50 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-30 11:48 Mel Gorman [this message]
2021-03-30 11:51 ` Colin Ian King

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210330114847.GX3697@techsingularity.net \
    --to=mgorman@techsingularity.net \
    --cc=akpm@linux-foundation.org \
    --cc=colin.king@canonical.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --subject='Re: [PATCH] mm/page_alloc: Add a bulk page allocator -fix -fix' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox