linux-kernel - [RFC 4/4] mm: Ignore cpuset enforcement when allocation flag has __GFP

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Message-Id: <1479824388-30446-5-git-send-email-khandual@linux.vnet.ibm.com>
Date:   Tue, 22 Nov 2016 19:49:40 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...e.com, vbabka@...e.cz, mgorman@...e.de,
        minchan@...nel.org, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, srikar@...ux.vnet.ibm.com,
        haren@...ux.vnet.ibm.com, jglisse@...hat.com, dave.hansen@...el.com
Subject: [RFC 4/4] mm: Ignore cpuset enforcement when allocation flag has __GFP_THISNODE

__GFP_THISNODE specifically asks the memory to be allocated from the given
node. Not all the requests that end up in __alloc_pages_nodemask() are
originated from the process context where cpuset makes more sense. The
current condition enforces cpuset limitation on every allocation whether
originated from process context or not which prevents __GFP_THISNODE
mandated allocations to come from the specified node. In context of the
coherent device memory node which is isolated from all cpuset nodemask
in the system, it prevents the only way of allocation into it which has
been changed with this patch.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 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 6de9440..1697e21 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3715,7 +3715,7 @@ struct page *
 		.migratetype = gfpflags_to_migratetype(gfp_mask),
 	};

-	if (cpusets_enabled()) {
+	if (cpusets_enabled() && !(alloc_mask & __GFP_THISNODE)) {
 		alloc_mask |= __GFP_HARDWALL;
 		alloc_flags |= ALLOC_CPUSET;
 		if (!ac.nodemask)
-- 
1.8.3.1