On 7/29/19 7:28 AM, Christoph Hellwig wrote:
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@xxxxxx>
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
---
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);
MIGRATE_PFN_WRITE may mot being used but that seems like a bug to me.
If a page is migrated to device memory, it could be mapped at the same
time to avoid a device page fault but it would need the flag to know
whether to map it RW or RO. But I suppose that could be inferred from
the vma->vm_flags.
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