Merge /spare/repo/linux-2.6/

1 files changed, 29 insertions, 19 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 6fe77acbc1cd..e046b7e4b530 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -913,9 +913,13 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         pud = pud_offset(pgd, pg);
                         BUG_ON(pud_none(*pud));
                         pmd = pmd_offset(pud, pg);
-                        BUG_ON(pmd_none(*pmd));
+                        if (pmd_none(*pmd))
+                                return i ? : -EFAULT;
                         pte = pte_offset_map(pmd, pg);
-                        BUG_ON(pte_none(*pte));
+                        if (pte_none(*pte)) {
+                                pte_unmap(pte);
+                                return i ? : -EFAULT;
+                        }
                         if (pages) {
                                 pages[i] = pte_page(*pte);
                                 get_page(pages[i]);
@@ -940,11 +944,13 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 }
                 spin_lock(&mm->page_table_lock);
                 do {
+                        int write_access = write;
                         struct page *page;
-                        int lookup_write = write;
 
                         cond_resched_lock(&mm->page_table_lock);
-                        while (!(page = follow_page(mm, start, lookup_write))) {
+                        while (!(page = follow_page(mm, start, write_access))) {
+                                int ret;
+
                                 /*
                                  * Shortcut for anonymous pages. We don't want
                                  * to force the creation of pages tables for
@@ -952,13 +958,23 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                  * nobody touched so far. This is important
                                  * for doing a core dump for these mappings.
                                  */
-                                if (!lookup_write &&
-                                    untouched_anonymous_page(mm,vma,start)) {
+                                if (!write && untouched_anonymous_page(mm,vma,start)) {
                                         page = ZERO_PAGE(start);
                                         break;
                                 }
                                 spin_unlock(&mm->page_table_lock);
-                                switch (handle_mm_fault(mm,vma,start,write)) {
+                                ret = __handle_mm_fault(mm, vma, start, write_access);
+
+                                /*
+                                 * The VM_FAULT_WRITE bit tells us that do_wp_page has
+                                 * broken COW when necessary, even if maybe_mkwrite
+                                 * decided not to set pte_write. We can thus safely do
+                                 * subsequent page lookups as if they were reads.
+                                 */
+                                if (ret & VM_FAULT_WRITE)
+                                        write_access = 0;
+                                
+                                switch (ret & ~VM_FAULT_WRITE) {
                                 case VM_FAULT_MINOR:
                                         tsk->min_flt++;
                                         break;
@@ -972,14 +988,6 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 default:
                                         BUG();
                                 }
-                                /*
-                                 * Now that we have performed a write fault
-                                 * and surely no longer have a shared page we
-                                 * shouldn't write, we shouldn't ignore an
-                                 * unwritable page in the page table if
-                                 * we are forcing write access.
-                                 */
-                                lookup_write = write && !force;
                                 spin_lock(&mm->page_table_lock);
                         }
                         if (pages) {
@@ -1229,6 +1237,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         struct page *old_page, *new_page;
         unsigned long pfn = pte_pfn(pte);
         pte_t entry;
+        int ret;
 
         if (unlikely(!pfn_valid(pfn))) {
                 /*
@@ -1256,7 +1265,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
                         lazy_mmu_prot_update(entry);
                         pte_unmap(page_table);
                         spin_unlock(&mm->page_table_lock);
-                        return VM_FAULT_MINOR;
+                        return VM_FAULT_MINOR|VM_FAULT_WRITE;
                 }
         }
         pte_unmap(page_table);
@@ -1283,6 +1292,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         /*
          * Re-check the pte - we dropped the lock
          */
+        ret = VM_FAULT_MINOR;
         spin_lock(&mm->page_table_lock);
         page_table = pte_offset_map(pmd, address);
         if (likely(pte_same(*page_table, pte))) {
@@ -1299,12 +1309,13 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
 
                 /* Free the old page.. */
                 new_page = old_page;
+                ret |= VM_FAULT_WRITE;
         }
         pte_unmap(page_table);
         page_cache_release(new_page);
         page_cache_release(old_page);
         spin_unlock(&mm->page_table_lock);
-        return VM_FAULT_MINOR;
+        return ret;
 
 no_new_page:
         page_cache_release(old_page);
@@ -1996,7 +2007,6 @@ static inline int handle_pte_fault(struct mm_struct *mm,
         if (write_access) {
                 if (!pte_write(entry))
                         return do_wp_page(mm, vma, address, pte, pmd, entry);
-
                 entry = pte_mkdirty(entry);
         }
         entry = pte_mkyoung(entry);
@@ -2011,7 +2021,7 @@ static inline int handle_pte_fault(struct mm_struct *mm,
 /*
  * By the time we get here, we already hold the mm semaphore
  */
-int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
+int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
                 unsigned long address, int write_access)
 {
         pgd_t *pgd;