linux-kernel - [PATCH 9/9] mm: remove the MIGRATE_PFN

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Message-Id: <20190729142843.22320-10-hch@lst.de>
Date:   Mon, 29 Jul 2019 17:28:43 +0300
From:   Christoph Hellwig <hch@....de>
To:     Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>
Cc:     Ralph Campbell <rcampbell@...dia.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 9/9] mm: remove the MIGRATE_PFN_WRITE flag

The MIGRATE_PFN_WRITE is only used locally in migrate_vma_collect_pmd,
where it can be replaced with a simple boolean local variable.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/linux/migrate.h | 1 -
 mm/migrate.c            | 9 +++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 8b46cfdb1a0e..ba74ef5a7702 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -165,7 +165,6 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 #define MIGRATE_PFN_VALID	(1UL << 0)
 #define MIGRATE_PFN_MIGRATE	(1UL << 1)
 #define MIGRATE_PFN_LOCKED	(1UL << 2)
-#define MIGRATE_PFN_WRITE	(1UL << 3)
 #define MIGRATE_PFN_SHIFT	6
 
 static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
diff --git a/mm/migrate.c b/mm/migrate.c
index 74735256e260..724f92dcc31b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2212,6 +2212,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 		unsigned long mpfn, pfn;
 		struct page *page;
 		swp_entry_t entry;
+		bool writable = false;
 		pte_t pte;
 
 		pte = *ptep;
@@ -2240,7 +2241,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			mpfn = migrate_pfn(page_to_pfn(page)) |
 					MIGRATE_PFN_MIGRATE;
 			if (is_write_device_private_entry(entry))
-				mpfn |= MIGRATE_PFN_WRITE;
+				writable = true;
 		} else {
 			if (is_zero_pfn(pfn)) {
 				mpfn = MIGRATE_PFN_MIGRATE;
@@ -2250,7 +2251,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			}
 			page = vm_normal_page(migrate->vma, addr, pte);
 			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
-			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
+			if (pte_write(pte))
+				writable = true;
 		}
 
 		/* FIXME support THP */
@@ -2284,8 +2286,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			ptep_get_and_clear(mm, addr, ptep);
 
 			/* Setup special migration page table entry */
-			entry = make_migration_entry(page, mpfn &
-						     MIGRATE_PFN_WRITE);
+			entry = make_migration_entry(page, writable);
 			swp_pte = swp_entry_to_pte(entry);
 			if (pte_soft_dirty(pte))
 				swp_pte = pte_swp_mksoft_dirty(swp_pte);
-- 
2.20.1