1 files changed, 73 insertions, 80 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 9c6ff7fffdc..e6c99f6b564 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1831,6 +1831,13 @@ static int unmap_mapping_range_vma(struct vm_area_struct *vma,
         unsigned long restart_addr;
         int need_break;
 
+        /*
+         * files that support invalidating or truncating portions of the
+         * file from under mmaped areas must set the VM_CAN_INVALIDATE flag, and
+         * have their .nopage function return the page locked.
+         */
+        BUG_ON(!(vma->vm_flags & VM_CAN_INVALIDATE));
+
 again:
         restart_addr = vma->vm_truncate_count;
         if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
@@ -1959,17 +1966,8 @@ void unmap_mapping_range(struct address_space *mapping,
 
         spin_lock(&mapping->i_mmap_lock);
 
-        /* serialize i_size write against truncate_count write */
-        smp_wmb();
-        /* Protect against page faults, and endless unmapping loops */
+        /* Protect against endless unmapping loops */
         mapping->truncate_count++;
-        /*
-         * For archs where spin_lock has inclusive semantics like ia64
-         * this smp_mb() will prevent to read pagetable contents
-         * before the truncate_count increment is visible to
-         * other cpus.
-         */
-        smp_mb();
         if (unlikely(is_restart_addr(mapping->truncate_count))) {
                 if (mapping->truncate_count == 0)
                         reset_vma_truncate_counts(mapping);
@@ -2008,8 +2006,18 @@ int vmtruncate(struct inode * inode, loff_t offset)
         if (IS_SWAPFILE(inode))
                 goto out_busy;
         i_size_write(inode, offset);
+
+        /*
+         * unmap_mapping_range is called twice, first simply for efficiency
+         * so that truncate_inode_pages does fewer single-page unmaps. However
+         * after this first call, and before truncate_inode_pages finishes,
+         * it is possible for private pages to be COWed, which remain after
+         * truncate_inode_pages finishes, hence the second unmap_mapping_range
+         * call must be made for correctness.
+         */
         unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
         truncate_inode_pages(mapping, offset);
+        unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
         goto out_truncate;
 
 do_expand:
@@ -2049,6 +2057,7 @@ int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
         down_write(&inode->i_alloc_sem);
         unmap_mapping_range(mapping, offset, (end - offset), 1);
         truncate_inode_pages_range(mapping, offset, end);
+        unmap_mapping_range(mapping, offset, (end - offset), 1);
         inode->i_op->truncate_range(inode, offset, end);
         up_write(&inode->i_alloc_sem);
         mutex_unlock(&inode->i_mutex);
@@ -2206,7 +2215,6 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
         /* No need to invalidate - it was non-present before */
         update_mmu_cache(vma, address, pte);
-        lazy_mmu_prot_update(pte);
 unlock:
         pte_unmap_unlock(page_table, ptl);
 out:
@@ -2297,10 +2305,8 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 int write_access)
 {
         spinlock_t *ptl;
-        struct page *new_page;
-        struct address_space *mapping = NULL;
+        struct page *page, *nopage_page;
         pte_t entry;
-        unsigned int sequence = 0;
         int ret = VM_FAULT_MINOR;
         int anon = 0;
         struct page *dirty_page = NULL;
@@ -2308,74 +2314,53 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
         pte_unmap(page_table);
         BUG_ON(vma->vm_flags & VM_PFNMAP);
 
-        if (vma->vm_file) {
-                mapping = vma->vm_file->f_mapping;
-                sequence = mapping->truncate_count;
-                smp_rmb(); /* serializes i_size against truncate_count */
-        }
-retry:
-        new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
-        /*
-         * No smp_rmb is needed here as long as there's a full
-         * spin_lock/unlock sequence inside the ->nopage callback
-         * (for the pagecache lookup) that acts as an implicit
-         * smp_mb() and prevents the i_size read to happen
-         * after the next truncate_count read.
-         */
-
+        nopage_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
         /* no page was available -- either SIGBUS, OOM or REFAULT */
-        if (unlikely(new_page == NOPAGE_SIGBUS))
+        if (unlikely(nopage_page == NOPAGE_SIGBUS))
                 return VM_FAULT_SIGBUS;
-        else if (unlikely(new_page == NOPAGE_OOM))
+        else if (unlikely(nopage_page == NOPAGE_OOM))
                 return VM_FAULT_OOM;
-        else if (unlikely(new_page == NOPAGE_REFAULT))
+        else if (unlikely(nopage_page == NOPAGE_REFAULT))
                 return VM_FAULT_MINOR;
 
+        BUG_ON(vma->vm_flags & VM_CAN_INVALIDATE && !PageLocked(nopage_page));
+        /*
+         * For consistency in subsequent calls, make the nopage_page always
+         * locked.
+         */
+        if (unlikely(!(vma->vm_flags & VM_CAN_INVALIDATE)))
+                lock_page(nopage_page);
+
         /*
          * Should we do an early C-O-W break?
          */
+        page = nopage_page;
         if (write_access) {
                 if (!(vma->vm_flags & VM_SHARED)) {
-                        struct page *page;
-
-                        if (unlikely(anon_vma_prepare(vma)))
-                                goto oom;
-                        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
-                                                vma, address);
-                        if (!page)
-                                goto oom;
-                        copy_user_highpage(page, new_page, address, vma);
-                        page_cache_release(new_page);
-                        new_page = page;
+                        if (unlikely(anon_vma_prepare(vma))) {
+                                ret = VM_FAULT_OOM;
+                                goto out_error;
+                        }
+                        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+                        if (!page) {
+                                ret = VM_FAULT_OOM;
+                                goto out_error;
+                        }
+                        copy_user_highpage(page, nopage_page, address, vma);
                         anon = 1;
-
                 } else {
                         /* if the page will be shareable, see if the backing
                          * address space wants to know that the page is about
                          * to become writable */
                         if (vma->vm_ops->page_mkwrite &&
-                            vma->vm_ops->page_mkwrite(vma, new_page) < 0
-                            ) {
-                                page_cache_release(new_page);
-                                return VM_FAULT_SIGBUS;
+                            vma->vm_ops->page_mkwrite(vma, page) < 0) {
+                                ret = VM_FAULT_SIGBUS;
+                                goto out_error;
                         }
                 }
         }
 
         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
-        /*
-         * For a file-backed vma, someone could have truncated or otherwise
-         * invalidated this page.  If unmap_mapping_range got called,
-         * retry getting the page.
-         */
-        if (mapping && unlikely(sequence != mapping->truncate_count)) {
-                pte_unmap_unlock(page_table, ptl);
-                page_cache_release(new_page);
-                cond_resched();
-                sequence = mapping->truncate_count;
-                smp_rmb();
-                goto retry;
-        }
 
         /*
          * This silly early PAGE_DIRTY setting removes a race
@@ -2388,43 +2373,51 @@ retry:
          * handle that later.
          */
         /* Only go through if we didn't race with anybody else... */
-        if (pte_none(*page_table)) {
-                flush_icache_page(vma, new_page);
-                entry = mk_pte(new_page, vma->vm_page_prot);
+        if (likely(pte_none(*page_table))) {
+                flush_icache_page(vma, page);
+                entry = mk_pte(page, vma->vm_page_prot);
                 if (write_access)
                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
                 set_pte_at(mm, address, page_table, entry);
                 if (anon) {
-                        inc_mm_counter(mm, anon_rss);
-                        lru_cache_add_active(new_page);
-                        page_add_new_anon_rmap(new_page, vma, address);
+                        inc_mm_counter(mm, anon_rss);
+                        lru_cache_add_active(page);
+                        page_add_new_anon_rmap(page, vma, address);
                 } else {
                         inc_mm_counter(mm, file_rss);
-                        page_add_file_rmap(new_page);
+                        page_add_file_rmap(page);
                         if (write_access) {
-                                dirty_page = new_page;
+                                dirty_page = page;
                                 get_page(dirty_page);
                         }
                 }
+
+                /* no need to invalidate: a not-present page won't be cached */
+                update_mmu_cache(vma, address, entry);
+                lazy_mmu_prot_update(entry);
         } else {
-                /* One of our sibling threads was faster, back out. */
-                page_cache_release(new_page);
-                goto unlock;
+                if (anon)
+                        page_cache_release(page);
+                else
+                        anon = 1; /* not anon, but release nopage_page */
         }
 
-        /* no need to invalidate: a not-present page shouldn't be cached */
-        update_mmu_cache(vma, address, entry);
-        lazy_mmu_prot_update(entry);
-unlock:
         pte_unmap_unlock(page_table, ptl);
-        if (dirty_page) {
+
+out:
+        unlock_page(nopage_page);
+        if (anon)
+                page_cache_release(nopage_page);
+        else if (dirty_page) {
                 set_page_dirty_balance(dirty_page);
                 put_page(dirty_page);
         }
+
         return ret;
-oom:
-        page_cache_release(new_page);
-        return VM_FAULT_OOM;
+
+out_error:
+        anon = 1; /* relase nopage_page */
+        goto out;
 }
 
 /*