linux-kernel - [RFC PATCH v2 1/5] mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always available

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Date:   Mon,  6 Jul 2020 20:20:47 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Alan Cox <alan@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Christopher Lameter <cl@...ux.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Idan Yaniv <idan.yaniv@....com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Mike Rapoport <rppt@...ux.ibm.com>
Subject: [RFC PATCH v2 1/5] mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always available

From: Mike Rapoport <rppt@...ux.ibm.com>

The definitions of shift, mask and size for the second and the third level
of the leaf pages are available only when CONFIG_TRANSPARENT_HUGEPAGE is
set. Otherwise they evaluate to BUILD_BUG().

There is no explanation neither in the code nor in the changelog why the
usage of, e.g. HPAGE_PMD_SIZE should be only allowed with THP and forbidden
otherwise while the definitions of HPAGE_PMD_SIZE and HPAGE_PUD_SIZE
express the sizes better than ambiguous HPAGE_SIZE.

Make HPAGE_PxD_{SHIFT,MASK,SIZE} definitions available unconditionally.

Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
 include/linux/huge_mm.h | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 71f20776b06c..1f4b44a76e31 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -115,7 +115,6 @@ extern struct kobj_attribute shmem_enabled_attr;
 #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
 #define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define HPAGE_PMD_SHIFT PMD_SHIFT
 #define HPAGE_PMD_SIZE	((1UL) << HPAGE_PMD_SHIFT)
 #define HPAGE_PMD_MASK	(~(HPAGE_PMD_SIZE - 1))
@@ -124,6 +123,8 @@ extern struct kobj_attribute shmem_enabled_attr;
 #define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
 #define HPAGE_PUD_MASK	(~(HPAGE_PUD_SIZE - 1))
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+
 extern unsigned long transparent_hugepage_flags;
 
 /*
@@ -316,13 +317,6 @@ static inline struct list_head *page_deferred_list(struct page *page)
 }
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
-#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
-#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
-#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })
-
-#define HPAGE_PUD_SHIFT ({ BUILD_BUG(); 0; })
-#define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
-#define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
 static inline int hpage_nr_pages(struct page *page)
 {
-- 
2.26.2