+ mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch added to -mm tree

+ mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/page_alloc: Add a bulk page allocator -fix -fix
has been added to the -mm tree.  Its filename is
     mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch

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------------------------------------------------------
From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm/page_alloc: Add a bulk page allocator -fix -fix

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.

Link: https://lkml.kernel.org/r/20210330114847.GX3697@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Colin Ian King <colin.king@canonical.com>
Tested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_alloc-add-a-bulk-page-allocator-fix-fix
+++ a/mm/page_alloc.c
@@ -5031,7 +5031,7 @@ unsigned long __alloc_pages_bulk(gfp_t g
 	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))
_

Patches currently in -mm which might be from mgorman@techsingularity.net are

mm-page_alloc-rename-alloced-to-allocated.patch
mm-page_alloc-add-a-bulk-page-allocator.patch
mm-page_alloc-add-a-bulk-page-allocator-fix.patch
mm-page_alloc-add-a-bulk-page-allocator-fix-fix.patch
mm-page_alloc-add-an-array-based-interface-to-the-bulk-page-allocator.patch