1 files changed, 34 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7d20b25c58fc..449841413cf1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -15,6 +15,7 @@
 #include <linux/fs.h>
 #include <linux/mutex.h>
 #include <linux/debug_locks.h>
+#include <linux/backing-dev.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -810,6 +811,39 @@ struct shrinker;
 extern struct shrinker *set_shrinker(int, shrinker_t);
 extern void remove_shrinker(struct shrinker *shrinker);
 
+/*
+ * Some shared mappigns will want the pages marked read-only
+ * to track write events. If so, we'll downgrade vm_page_prot
+ * to the private version (using protection_map[] without the
+ * VM_SHARED bit).
+ */
+static inline int vma_wants_writenotify(struct vm_area_struct *vma)
+{
+        unsigned int vm_flags = vma->vm_flags;
+
+        /* If it was private or non-writable, the write bit is already clear */
+        if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
+                return 0;
+
+        /* The backer wishes to know when pages are first written to? */
+        if (vma->vm_ops && vma->vm_ops->page_mkwrite)
+                return 1;
+
+        /* The open routine did something to the protections already? */
+        if (pgprot_val(vma->vm_page_prot) !=
+            pgprot_val(protection_map[vm_flags &
+                    (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]))
+                return 0;
+
+        /* Specialty mapping? */
+        if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
+                return 0;
+
+        /* Can the mapping track the dirty pages? */
+        return vma->vm_file && vma->vm_file->f_mapping &&
+                mapping_cap_account_dirty(vma->vm_file->f_mapping);
+}
+
 extern pte_t *FASTCALL(get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl));
 
 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address);