linux-kernel - [PATCH] mm: hugetlb: remove minimum

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Date:   Thu, 16 Jun 2022 11:38:46 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     mike.kravetz@...cle.com, songmuchun@...edance.com,
        akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mm: hugetlb: remove minimum_order variable

The following commit:

  commit 641844f5616d ("mm/hugetlb: introduce minimum hugepage order")

fixed a static checker warning and introduced a global variable minimum_order
to fix the warning.  However, the local variable in dissolve_free_huge_pages()
can be initialized to huge_page_order(&default_hstate) to fix the warning.
So remove minimum_order to simplify the code.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/hugetlb.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8ea4e51d8186..405d1c7441c9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -66,12 +66,6 @@ static bool hugetlb_cma_page(struct page *page, unsigned int order)
 #endif
 static unsigned long hugetlb_cma_size __initdata;
 
-/*
- * Minimum page order among possible hugepage sizes, set to a proper value
- * at boot time.
- */
-static unsigned int minimum_order __read_mostly = UINT_MAX;
-
 __initdata LIST_HEAD(huge_boot_pages);
 
 /* for command line parsing */
@@ -2161,11 +2155,17 @@ int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
 	unsigned long pfn;
 	struct page *page;
 	int rc = 0;
+	unsigned int order;
+	struct hstate *h;
 
 	if (!hugepages_supported())
 		return rc;
 
-	for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
+	order = huge_page_order(&default_hstate);
+	for_each_hstate(h)
+		order = min(order, huge_page_order(h));
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order) {
 		page = pfn_to_page(pfn);
 		rc = dissolve_free_huge_page(page);
 		if (rc)
@@ -3157,9 +3157,6 @@ static void __init hugetlb_init_hstates(void)
 	struct hstate *h, *h2;
 
 	for_each_hstate(h) {
-		if (minimum_order > huge_page_order(h))
-			minimum_order = huge_page_order(h);
-
 		/* oversize hugepages were init'ed in early boot */
 		if (!hstate_is_gigantic(h))
 			hugetlb_hstate_alloc_pages(h);
@@ -3184,7 +3181,6 @@ static void __init hugetlb_init_hstates(void)
 				h->demote_order = h2->order;
 		}
 	}
-	VM_BUG_ON(minimum_order == UINT_MAX);
 }
 
 static void __init report_hugepages(void)
-- 
2.11.0