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From:   Doug Berger <opendmb@gmail.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Jonathan Corbet <corbet@lwn.net>, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
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        Randy Dunlap <rdunlap@infradead.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Doug Berger <opendmb@gmail.com>,
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        - <devicetree-spec@vger.kernel.org>,
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        linux-mm@kvack.org, iommu@lists.linux.dev
Subject: [PATCH 10/21] mm/page_alloc.c: allow oversized movablecore
Date:   Tue, 13 Sep 2022 12:54:57 -0700
Message-Id: <20220913195508.3511038-11-opendmb@gmail.com>
In-Reply-To: <20220913195508.3511038-1-opendmb@gmail.com>
References: <20220913195508.3511038-1-opendmb@gmail.com>
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Now that the error in computation of corepages has been corrected
by commit 9fd745d450e7 ("mm: fix overflow in
find_zone_movable_pfns_for_nodes()"), oversized specifications of
movablecore will result in a zero value for required_kernelcore if
it is not also specified.

It is unintuitive for such a request to lead to no ZONE_MOVABLE
memory when the kernel parameters are clearly requesting some.

The current behavior when requesting an oversized kernelcore is to
classify all of the pages in movable_zone as kernelcore. The new
behavior when requesting an oversized movablecore (when not also
specifying kernelcore) is to similarly classify all of the pages
in movable_zone as movablecore.

Signed-off-by: Doug Berger <opendmb@gmail.com>
---
 mm/page_alloc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b6074961fb59..ad38a81203e5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8041,13 +8041,13 @@ static void __init find_zone_movable_pfns_for_nodes(void)
 		corepages = totalpages - required_movablecore;
 
 		required_kernelcore = max(required_kernelcore, corepages);
+	} else if (!required_kernelcore) {
+		/* If kernelcore was not specified, there is no ZONE_MOVABLE */
+		goto out;
 	}
 
-	/*
-	 * If kernelcore was not specified or kernelcore size is larger
-	 * than totalpages, there is no ZONE_MOVABLE.
-	 */
-	if (!required_kernelcore || required_kernelcore >= totalpages)
+	/* If kernelcore size exceeds totalpages, there is no ZONE_MOVABLE */
+	if (required_kernelcore >= totalpages)
 		goto out;
 
 	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
-- 
2.25.1