1 files changed, 116 insertions, 20 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index ccc3ecf7cb98..450cebdabfc0 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  */
-static void
+static int
 truncate_complete_page(struct address_space *mapping, struct page *page)
 {
         if (page->mapping != mapping)
-                return;
+                return -EIO;
 
         if (page_has_private(page))
                 do_invalidatepage(page, 0);
@@ -108,6 +108,7 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
         remove_from_page_cache(page);
         ClearPageMappedToDisk(page);
         page_cache_release(page);       /* pagecache ref */
+        return 0;
 }
 
 /*
@@ -135,6 +136,51 @@ invalidate_complete_page(struct address_space *mapping, struct page *page)
         return ret;
 }
 
+int truncate_inode_page(struct address_space *mapping, struct page *page)
+{
+        if (page_mapped(page)) {
+                unmap_mapping_range(mapping,
+                                   (loff_t)page->index << PAGE_CACHE_SHIFT,
+                                   PAGE_CACHE_SIZE, 0);
+        }
+        return truncate_complete_page(mapping, page);
+}
+
+/*
+ * Used to get rid of pages on hardware memory corruption.
+ */
+int generic_error_remove_page(struct address_space *mapping, struct page *page)
+{
+        if (!mapping)
+                return -EINVAL;
+        /*
+         * Only punch for normal data pages for now.
+         * Handling other types like directories would need more auditing.
+         */
+        if (!S_ISREG(mapping->host->i_mode))
+                return -EIO;
+        return truncate_inode_page(mapping, page);
+}
+EXPORT_SYMBOL(generic_error_remove_page);
+
+/*
+ * Safely invalidate one page from its pagecache mapping.
+ * It only drops clean, unused pages. The page must be locked.
+ *
+ * Returns 1 if the page is successfully invalidated, otherwise 0.
+ */
+int invalidate_inode_page(struct page *page)
+{
+        struct address_space *mapping = page_mapping(page);
+        if (!mapping)
+                return 0;
+        if (PageDirty(page) || PageWriteback(page))
+                return 0;
+        if (page_mapped(page))
+                return 0;
+        return invalidate_complete_page(mapping, page);
+}
+
 /**
  * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
  * @mapping: mapping to truncate
@@ -196,12 +242,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
                                 unlock_page(page);
                                 continue;
                         }
-                        if (page_mapped(page)) {
-                                unmap_mapping_range(mapping,
-                                  (loff_t)page_index<<PAGE_CACHE_SHIFT,
-                                  PAGE_CACHE_SIZE, 0);
-                        }
-                        truncate_complete_page(mapping, page);
+                        truncate_inode_page(mapping, page);
                         unlock_page(page);
                 }
                 pagevec_release(&pvec);
@@ -238,15 +279,10 @@ void truncate_inode_pages_range(struct address_space *mapping,
                                 break;
                         lock_page(page);
                         wait_on_page_writeback(page);
-                        if (page_mapped(page)) {
-                                unmap_mapping_range(mapping,
-                                  (loff_t)page->index<<PAGE_CACHE_SHIFT,
-                                  PAGE_CACHE_SIZE, 0);
-                        }
+                        truncate_inode_page(mapping, page);
                         if (page->index > next)
                                 next = page->index;
                         next++;
-                        truncate_complete_page(mapping, page);
                         unlock_page(page);
                 }
                 pagevec_release(&pvec);
@@ -311,12 +347,8 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
                         if (lock_failed)
                                 continue;
 
-                        if (PageDirty(page) || PageWriteback(page))
-                                goto unlock;
-                        if (page_mapped(page))
-                                goto unlock;
-                        ret += invalidate_complete_page(mapping, page);
-unlock:
+                        ret += invalidate_inode_page(page);
+
                         unlock_page(page);
                         if (next > end)
                                 break;
@@ -465,3 +497,67 @@ int invalidate_inode_pages2(struct address_space *mapping)
         return invalidate_inode_pages2_range(mapping, 0, -1);
 }
 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
+
+/**
+ * truncate_pagecache - unmap and remove pagecache that has been truncated
+ * @inode: inode
+ * @old: old file offset
+ * @new: new file offset
+ *
+ * inode's new i_size must already be written before truncate_pagecache
+ * is called.
+ *
+ * This function should typically be called before the filesystem
+ * releases resources associated with the freed range (eg. deallocates
+ * blocks). This way, pagecache will always stay logically coherent
+ * with on-disk format, and the filesystem would not have to deal with
+ * situations such as writepage being called for a page that has already
+ * had its underlying blocks deallocated.
+ */
+void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
+{
+        if (new < old) {
+                struct address_space *mapping = inode->i_mapping;
+
+                /*
+                 * 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, new + PAGE_SIZE - 1, 0, 1);
+                truncate_inode_pages(mapping, new);
+                unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
+        }
+}
+EXPORT_SYMBOL(truncate_pagecache);
+
+/**
+ * vmtruncate - unmap mappings "freed" by truncate() syscall
+ * @inode: inode of the file used
+ * @offset: file offset to start truncating
+ *
+ * NOTE! We have to be ready to update the memory sharing
+ * between the file and the memory map for a potential last
+ * incomplete page.  Ugly, but necessary.
+ */
+int vmtruncate(struct inode *inode, loff_t offset)
+{
+        loff_t oldsize;
+        int error;
+
+        error = inode_newsize_ok(inode, offset);
+        if (error)
+                return error;
+        oldsize = inode->i_size;
+        i_size_write(inode, offset);
+        truncate_pagecache(inode, oldsize, offset);
+        if (inode->i_op->truncate)
+                inode->i_op->truncate(inode);
+
+        return error;
+}
+EXPORT_SYMBOL(vmtruncate);