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-rw-r--r--mm/memory.c117
1 files changed, 68 insertions, 49 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 97839f5..e70685f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1983,6 +1983,65 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page,
}
/*
+ * Handle write page faults for pages that can be reused in the current vma
+ *
+ * This can happen either due to the mapping being with the VM_SHARED flag,
+ * or due to us being the last reference standing to the page. In either
+ * case, all we need to do here is to mark the page as writable and update
+ * any related book-keeping.
+ */
+static inline int wp_page_reuse(struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long address,
+ pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
+ struct page *page, int page_mkwrite,
+ int dirty_shared)
+ __releases(ptl)
+{
+ pte_t entry;
+ /*
+ * Clear the pages cpupid information as the existing
+ * information potentially belongs to a now completely
+ * unrelated process.
+ */
+ if (page)
+ page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
+
+ flush_cache_page(vma, address, pte_pfn(orig_pte));
+ entry = pte_mkyoung(orig_pte);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ if (ptep_set_access_flags(vma, address, page_table, entry, 1))
+ update_mmu_cache(vma, address, page_table);
+ pte_unmap_unlock(page_table, ptl);
+
+ if (dirty_shared) {
+ struct address_space *mapping;
+ int dirtied;
+
+ if (!page_mkwrite)
+ lock_page(page);
+
+ dirtied = set_page_dirty(page);
+ VM_BUG_ON_PAGE(PageAnon(page), page);
+ mapping = page->mapping;
+ unlock_page(page);
+ page_cache_release(page);
+
+ if ((dirtied || page_mkwrite) && mapping) {
+ /*
+ * Some device drivers do not set page.mapping
+ * but still dirty their pages
+ */
+ balance_dirty_pages_ratelimited(mapping);
+ }
+
+ if (!page_mkwrite)
+ file_update_time(vma->vm_file);
+ }
+
+ return VM_FAULT_WRITE;
+}
+
+/*
* This routine handles present pages, when users try to write
* to a shared page. It is done by copying the page to a new address
* and decrementing the shared-page counter for the old page.
@@ -2008,8 +2067,6 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page *old_page, *new_page = NULL;
pte_t entry;
int ret = 0;
- int page_mkwrite = 0;
- bool dirty_shared = false;
unsigned long mmun_start = 0; /* For mmu_notifiers */
unsigned long mmun_end = 0; /* For mmu_notifiers */
struct mem_cgroup *memcg;
@@ -2026,7 +2083,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
(VM_WRITE|VM_SHARED))
- goto reuse;
+ return wp_page_reuse(mm, vma, address, page_table, ptl,
+ orig_pte, old_page, 0, 0);
goto gotten;
}
@@ -2055,12 +2113,16 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
page_move_anon_rmap(old_page, vma, address);
unlock_page(old_page);
- goto reuse;
+ return wp_page_reuse(mm, vma, address, page_table, ptl,
+ orig_pte, old_page, 0, 0);
}
unlock_page(old_page);
} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
(VM_WRITE|VM_SHARED))) {
+ int page_mkwrite = 0;
+
page_cache_get(old_page);
+
/*
* Only catch write-faults on shared writable pages,
* read-only shared pages can get COWed by
@@ -2091,51 +2153,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
page_mkwrite = 1;
}
- dirty_shared = true;
-
-reuse:
- /*
- * Clear the pages cpupid information as the existing
- * information potentially belongs to a now completely
- * unrelated process.
- */
- if (old_page)
- page_cpupid_xchg_last(old_page, (1 << LAST_CPUPID_SHIFT) - 1);
-
- flush_cache_page(vma, address, pte_pfn(orig_pte));
- entry = pte_mkyoung(orig_pte);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- if (ptep_set_access_flags(vma, address, page_table, entry,1))
- update_mmu_cache(vma, address, page_table);
- pte_unmap_unlock(page_table, ptl);
- ret |= VM_FAULT_WRITE;
-
- if (dirty_shared) {
- struct address_space *mapping;
- int dirtied;
-
- if (!page_mkwrite)
- lock_page(old_page);
-
- dirtied = set_page_dirty(old_page);
- VM_BUG_ON_PAGE(PageAnon(old_page), old_page);
- mapping = old_page->mapping;
- unlock_page(old_page);
- page_cache_release(old_page);
-
- if ((dirtied || page_mkwrite) && mapping) {
- /*
- * Some device drivers do not set page.mapping
- * but still dirty their pages
- */
- balance_dirty_pages_ratelimited(mapping);
- }
-
- if (!page_mkwrite)
- file_update_time(vma->vm_file);
- }
-
- return ret;
+ return wp_page_reuse(mm, vma, address, page_table, ptl,
+ orig_pte, old_page, page_mkwrite, 1);
}
/*
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