From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E876C11F66 for ; Tue, 13 Jul 2021 15:21:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A2E06128E for ; Tue, 13 Jul 2021 15:21:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237070AbhGMPX4 (ORCPT ); Tue, 13 Jul 2021 11:23:56 -0400 Received: from outbound-smtp29.blacknight.com ([81.17.249.32]:56330 "EHLO outbound-smtp29.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236986AbhGMPXw (ORCPT ); Tue, 13 Jul 2021 11:23:52 -0400 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp29.blacknight.com (Postfix) with ESMTPS id 816B1BEC92 for ; Tue, 13 Jul 2021 16:21:01 +0100 (IST) Received: (qmail 14885 invoked from network); 13 Jul 2021 15:21:01 -0000 Received: from unknown (HELO stampy.112glenside.lan) (mgorman@techsingularity.net@[84.203.17.255]) by 81.17.254.9 with ESMTPA; 13 Jul 2021 15:21:01 -0000 From: Mel Gorman To: Andrew Morton Cc: Desmond Cheong Zhi Xi , Zhang Qiang , Yanfei Xu , Chuck Lever , Jesper Dangaard Brouer , Matteo Croce , Linux-MM , LKML , Mel Gorman Subject: [PATCH 3/4] mm/page_alloc: Further fix __alloc_pages_bulk() return value Date: Tue, 13 Jul 2021 16:20:59 +0100 Message-Id: <20210713152100.10381-4-mgorman@techsingularity.net> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210713152100.10381-1-mgorman@techsingularity.net> References: <20210713152100.10381-1-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chuck Lever The author of commit b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after checking populated elements") was possibly confused by the mixture of return values throughout the function. The API contract is clear that the function "Returns the number of pages on the list or array." It does not list zero as a unique return value with a special meaning. Therefore zero is a plausible return value only if @nr_pages is zero or less. Clean up the return logic to make it clear that the returned value is always the total number of pages in the array/list, not the number of pages that were allocated during this call. The only change in behavior with this patch is the value returned if prepare_alloc_pages() fails. To match the API contract, the number of pages currently in the array/list is returned in this case. The call site in __page_pool_alloc_pages_slow() also seems to be confused on this matter. It should be attended to by someone who is familiar with that code. [mel@techsingularity.net: Return nr_populated if 0 pages are requested] Signed-off-by: Chuck Lever Acked-by: Jesper Dangaard Brouer Signed-off-by: Mel Gorman --- mm/page_alloc.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 803414ce9264..c66f1e6204c2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5221,9 +5221,6 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, unsigned int alloc_flags = ALLOC_WMARK_LOW; int nr_populated = 0, nr_account = 0; - if (unlikely(nr_pages <= 0)) - return 0; - /* * Skip populated array elements to determine if any pages need * to be allocated before disabling IRQs. @@ -5231,9 +5228,13 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, while (page_array && nr_populated < nr_pages && page_array[nr_populated]) nr_populated++; + /* No pages requested? */ + if (unlikely(nr_pages <= 0)) + goto out; + /* Already populated array? */ if (unlikely(page_array && nr_pages - nr_populated == 0)) - return nr_populated; + goto out; /* Use the single page allocator for one page. */ if (nr_pages - nr_populated == 1) @@ -5255,7 +5256,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, gfp &= gfp_allowed_mask; alloc_gfp = gfp; if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags)) - return nr_populated; + goto out; gfp = alloc_gfp; /* Find an allowed local zone that meets the low watermark. */ @@ -5323,6 +5324,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account); zone_statistics(ac.preferred_zoneref->zone, zone, nr_account); +out: return nr_populated; failed_irq: @@ -5338,7 +5340,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, nr_populated++; } - return nr_populated; + goto out; } EXPORT_SYMBOL_GPL(__alloc_pages_bulk); -- 2.26.2