linux-kernel - Re: [PATCH v3] mm/hugetlb: avoid hardcoding while checking if cma is enable

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Message-ID: <b2a98ab7-0a36-ad3d-f40d-1cc9216c7961@oracle.com>
Date:   Thu, 9 Jul 2020 11:58:11 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        Roman Gushchin <guro@...com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>
Subject: Re: [PATCH v3] mm/hugetlb: avoid hardcoding while checking if cma is
 enable

Looks like this produced a warning in linux-next.  I suspect it is due to the
combination CONFIG_HUGETLB_PAGE && !CONFIG_CMA.

Instead of adding the routine hugetlb_cma_enabled() to scan the hugetlb_cma
array, could we just use a boolean as follows?  It can simply be set in
hugetlb_cma_reserve when we reserve CMA.
-- 
Mike Kravetz

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fab4485b9e52..92cb882cf287 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -46,6 +46,7 @@ unsigned int default_hstate_idx;
 struct hstate hstates[HUGE_MAX_HSTATE];
 
 static struct cma *hugetlb_cma[MAX_NUMNODES];
+static bool hugetlb_cma_enabled = false;
 
 /*
  * Minimum page order among possible hugepage sizes, set to a proper value
@@ -2571,7 +2572,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 
 	for (i = 0; i < h->max_huge_pages; ++i) {
 		if (hstate_is_gigantic(h)) {
-			if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) {
+			if (hugetlb_cma_enabled) {
 				pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
 				break;
 			}
@@ -5708,6 +5709,7 @@ void __init hugetlb_cma_reserve(int order)
 		reserved += size;
 		pr_info("hugetlb_cma: reserved %lu MiB on node %d\n",
 			size / SZ_1M, nid);
+		hugetlb_cma_enabled = true;
 
 		if (reserved >= hugetlb_cma_size)
 			break;