The patch titled
Read/Write migration entries: Make mprotect() convert write migration entries to read
has been removed from the -mm tree. Its filename is
read-write-migration-entries-make-mprotect-convert-write-migration.patch
This patch was probably dropped from -mm because
it has now been merged into a subsystem tree or
into Linus's tree, or because it was folded into
its parent patch in the -mm tree.
From: Christoph Lameter <clameter@xxxxxxx>
1. Introduce a new function make_migration_entry() to
isolate common code between copy_pte_range and change_pte_range.
2. Modify change_pte_range() to check for a migration entry.
If a write migration entry is found and there is a request for
a READ permissions then change the migration entry.
I am a bit concerned about the check of newprot. Are there other
values than PAGE_READONLY that indicate read only access?
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/swapops.h | 10 ++++++++++
mm/memory.c | 7 ++-----
mm/mprotect.c | 21 ++++++++++++++++++---
3 files changed, 30 insertions(+), 8 deletions(-)
diff -puN include/linux/swapops.h~read-write-migration-entries-make-mprotect-convert-write-migration include/linux/swapops.h
--- devel/include/linux/swapops.h~read-write-migration-entries-make-mprotect-convert-write-migration 2006-04-27 03:11:29.000000000 -0700
+++ devel-akpm/include/linux/swapops.h 2006-04-27 03:11:36.000000000 -0700
@@ -98,6 +98,11 @@ static inline struct page *migration_ent
return p;
}
+static inline void make_migration_entry_read(swp_entry_t *entry)
+{
+ *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
+}
+
extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address);
#else
@@ -105,8 +110,13 @@ extern void migration_entry_wait(struct
#define make_migration_entry(page, write) swp_entry(0, 0)
#define is_migration_entry(swp) 0
#define migration_entry_to_page(swp) NULL
+static inline void make_migration_entry_read(swp_entry_t *entryp) { }
static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address) { }
+static inline int is_write_migration_entry(swp_entry_t entry)
+{
+ return 0;
+}
#endif
diff -puN mm/memory.c~read-write-migration-entries-make-mprotect-convert-write-migration mm/memory.c
--- devel/mm/memory.c~read-write-migration-entries-make-mprotect-convert-write-migration 2006-04-27 03:11:29.000000000 -0700
+++ devel-akpm/mm/memory.c 2006-04-27 03:11:29.000000000 -0700
@@ -447,14 +447,11 @@ copy_one_pte(struct mm_struct *dst_mm, s
}
if (is_migration_entry(entry) &&
is_cow_mapping(vm_flags)) {
- page = migration_entry_to_page(entry);
-
/*
* COW mappings require pages in both parent
- * and child to be set to read.
+ * and child to be set to read.
*/
- entry = make_migration_entry(page,
- SWP_MIGRATION_READ);
+ make_migration_entry_read(&entry);
pte = swp_entry_to_pte(entry);
set_pte_at(src_mm, addr, src_pte, pte);
}
diff -puN mm/mprotect.c~read-write-migration-entries-make-mprotect-convert-write-migration mm/mprotect.c
--- devel/mm/mprotect.c~read-write-migration-entries-make-mprotect-convert-write-migration 2006-04-27 03:11:29.000000000 -0700
+++ devel-akpm/mm/mprotect.c 2006-04-27 03:11:29.000000000 -0700
@@ -19,6 +19,8 @@
#include <linux/mempolicy.h>
#include <linux/personality.h>
#include <linux/syscalls.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -28,22 +30,35 @@
static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
unsigned long addr, unsigned long end, pgprot_t newprot)
{
- pte_t *pte;
+ pte_t *pte, oldpte;
spinlock_t *ptl;
pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
do {
- if (pte_present(*pte)) {
+ oldpte = *pte;
+ if (pte_present(oldpte)) {
pte_t ptent;
/* Avoid an SMP race with hardware updated dirty/clean
* bits by wiping the pte and then setting the new pte
* into place.
*/
- ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot);
+ ptent = pte_modify(ptep_get_and_clear(mm, addr, pte),
+ newprot);
set_pte_at(mm, addr, pte, ptent);
lazy_mmu_prot_update(ptent);
+ } else
+ if (!pte_file(oldpte) && pgprot_val(newprot) ==
+ pgprot_val(PAGE_READONLY)) {
+ swp_entry_t entry = pte_to_swp_entry(oldpte);
+
+ if (is_write_migration_entry(entry)) {
+ make_migration_entry_read(&entry);
+ set_pte_at(mm, addr, pte,
+ swp_entry_to_pte(entry));
+ }
}
+
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap_unlock(pte - 1, ptl);
}
_
Patches currently in -mm which might be from clameter@xxxxxxx are
origin.patch
page-migration-make-do_swap_page-redo-the-fault.patch
slab-extract-cache_free_alien-from-__cache_free.patch
migration-remove-unnecessary-pageswapcache-checks.patch
read-write-migration-entries-make-mprotect-convert-write-migration.patch
read-write-migration-entries-make-mprotect-convert-write-migration-fix.patch
-
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