linux-kernel - [PATCH 04/10] kexec: separate PageHighMem() and PageHighMemZone() use case

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Message-Id: <1587369582-3882-5-git-send-email-iamjoonsoo.kim@lge.com>
Date:   Mon, 20 Apr 2020 16:59:36 +0900
From:   js1304@...il.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Vlastimil Babka <vbabka@...e.cz>,
        Laura Abbott <labbott@...hat.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Eric Biederman <ebiederm@...ssion.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH 04/10] kexec: separate PageHighMem() and PageHighMemZone() use case

From: Joonsoo Kim <iamjoonsoo.kim@....com>

Until now, PageHighMem() is used for two different cases. One is to check
if there is a direct mapping for this page or not. The other is to check
the zone of this page, that is, weather it is the highmem type zone or not.

Now, we have separate functions, PageHighMem() and PageHighMemZone() for
each cases. Use appropriate one.

Note that there are some rules to determine the proper macro.

1. If PageHighMem() is called for checking if the direct mapping exists
or not, use PageHighMem().
2. If PageHighMem() is used to predict the previous gfp_flags for
this page, use PageHighMemZone(). The zone of the page is related to
the gfp_flags.
3. If purpose of calling PageHighMem() is to count highmem page and
to interact with the system by using this count, use PageHighMemZone().
This counter is usually used to calculate the available memory for an
kernel allocation and pages on the highmem zone cannot be available
for an kernel allocation.
4. Otherwise, use PageHighMemZone(). It's safe since it's implementation
is just copy of the previous PageHighMem() implementation and won't
be changed.

I apply the rule #2 for this patch.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 kernel/kexec_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index ba1d91e..33097b7 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -766,7 +766,7 @@ static struct page *kimage_alloc_page(struct kimage *image,
 			 * gfp_flags honor the ones passed in.
 			 */
 			if (!(gfp_mask & __GFP_HIGHMEM) &&
-			    PageHighMem(old_page)) {
+			    PageHighMemZone(old_page)) {
 				kimage_free_pages(old_page);
 				continue;
 			}
-- 
2.7.4