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From:   Mel Gorman <mgorman@techsingularity.net>
To:     Linux-MM <linux-mm@kvack.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>, NeilBrown <neilb@suse.de>,
        Thierry Reding <thierry.reding@gmail.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        LKML <linux-kernel@vger.kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 1/6] mm/page_alloc: Rename ALLOC_HIGH to ALLOC_MIN_RESERVE
Date:   Tue, 29 Nov 2022 15:16:56 +0000
Message-Id: <20221129151701.23261-2-mgorman@techsingularity.net>
In-Reply-To: <20221129151701.23261-1-mgorman@techsingularity.net>
References: <20221129151701.23261-1-mgorman@techsingularity.net>
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__GFP_HIGH aliases to ALLOC_HIGH but the name does not really hint
what it means. As ALLOC_HIGH is internal to the allocator, rename
it to ALLOC_MIN_RESERVE to document that the min reserves can
be depleted.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/internal.h   | 4 +++-
 mm/page_alloc.c | 8 ++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 6b7ef495b56d..d503e57a57a1 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -744,7 +744,9 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 #endif
 
 #define ALLOC_HARDER		 0x10 /* try to alloc harder */
-#define ALLOC_HIGH		 0x20 /* __GFP_HIGH set */
+#define ALLOC_MIN_RESERVE	 0x20 /* __GFP_HIGH set. Allow access to 50%
+				       * of the min watermark.
+				       */
 #define ALLOC_CPUSET		 0x40 /* check for correct cpuset */
 #define ALLOC_CMA		 0x80 /* allow allocations from CMA areas */
 #ifdef CONFIG_ZONE_DMA32
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 218b28ee49ed..3b37909617bc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3981,7 +3981,7 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
 	/* free_pages may go negative - that's OK */
 	free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
 
-	if (alloc_flags & ALLOC_HIGH)
+	if (alloc_flags & ALLOC_MIN_RESERVE)
 		min -= min / 2;
 
 	if (unlikely(alloc_harder)) {
@@ -4823,18 +4823,18 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
 	unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
 
 	/*
-	 * __GFP_HIGH is assumed to be the same as ALLOC_HIGH
+	 * __GFP_HIGH is assumed to be the same as ALLOC_MIN_RESERVE
 	 * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
 	 * to save two branches.
 	 */
-	BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
+	BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_MIN_RESERVE);
 	BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
 
 	/*
 	 * The caller may dip into page reserves a bit more if the caller
 	 * cannot run direct reclaim, or if the caller has realtime scheduling
 	 * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
-	 * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
+	 * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_MIN_RESERVE(__GFP_HIGH).
 	 */
 	alloc_flags |= (__force int)
 		(gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
-- 
2.35.3