From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org,
        Gao Xiang <hsiangkao@linux.alibaba.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Michal Hocko <mhocko@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH] mm/page_alloc: avoid high-order page allocation warn with __GFP_NOFAIL
Date:   Sun,  5 Mar 2023 13:30:35 +0800
Message-Id: <20230305053035.1911-1-hsiangkao@linux.alibaba.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

My knowledge of this is somewhat limited, however, since vmalloc already
supported __GFP_NOFAIL in commit 9376130c390a ("mm/vmalloc: add
support for __GFP_NOFAIL").  __GFP_NOFAIL could trigger the following
stack and allocate high-order pages when CONFIG_HAVE_ARCH_HUGE_VMALLOC
is enabled:

 __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5549
 alloc_pages+0x1aa/0x270 mm/mempolicy.c:2286
 vm_area_alloc_pages mm/vmalloc.c:2989 [inline]
 __vmalloc_area_node mm/vmalloc.c:3057 [inline]
 __vmalloc_node_range+0x978/0x13c0 mm/vmalloc.c:3227
 kvmalloc_node+0x156/0x1a0 mm/util.c:606
 kvmalloc include/linux/slab.h:737 [inline]
 kvmalloc_array include/linux/slab.h:755 [inline]
 kvcalloc include/linux/slab.h:760 [inline]
 (codebase: Linux 6.2-rc2)

Don't warn such cases since high-order pages with __GFP_NOFAIL is
somewhat legel.

Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 mm/page_alloc.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0745aedebb37..0618716c49df 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3822,12 +3822,6 @@ struct page *rmqueue(struct zone *preferred_zone,
 {
 	struct page *page;
 
-	/*
-	 * We most definitely don't want callers attempting to
-	 * allocate greater than order-1 page units with __GFP_NOFAIL.
-	 */
-	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
-
 	if (likely(pcp_allowed_order(order))) {
 		/*
 		 * MIGRATE_MOVABLE pcplist could have the pages on CMA area and
-- 
2.24.4