2 files changed, 39 insertions, 7 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a06a84d347fb..92acae9f1f4c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -896,6 +896,8 @@ extern unsigned long do_brk(unsigned long, unsigned long);
 /* filemap.c */
 extern unsigned long page_unuse(struct page *);
 extern void truncate_inode_pages(struct address_space *, loff_t);
+extern void truncate_inode_pages_range(struct address_space *,
+                                       loff_t lstart, loff_t lend);
 
 /* generic vm_area_ops exported for stackable file systems */
 extern struct page *filemap_nopage(struct vm_area_struct *, unsigned long, int *);
diff --git a/mm/truncate.c b/mm/truncate.c
index 9173ab500604..7dee32745901 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -82,12 +82,15 @@ invalidate_complete_page(struct address_space *mapping, struct page *page)
 }
 
 /**
- * truncate_inode_pages - truncate *all* the pages from an offset
+ * truncate_inode_pages - truncate range of pages specified by start and
+ * end byte offsets
  * @mapping: mapping to truncate
  * @lstart: offset from which to truncate
+ * @lend: offset to which to truncate
  *
- * Truncate the page cache at a set offset, removing the pages that are beyond
- * that offset (and zeroing out partial pages).
+ * Truncate the page cache, removing the pages that are between
+ * specified offsets (and zeroing out partial page
+ * (if lstart is not page aligned)).
  *
  * Truncate takes two passes - the first pass is nonblocking.  It will not
  * block on page locks and it will not block on writeback.  The second pass
@@ -101,12 +104,12 @@ invalidate_complete_page(struct address_space *mapping, struct page *page)
  * We pass down the cache-hot hint to the page freeing code.  Even if the
  * mapping is large, it is probably the case that the final pages are the most
  * recently touched, and freeing happens in ascending file offset order.
- *
- * Called under (and serialised by) inode->i_sem.
  */
-void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
+void truncate_inode_pages_range(struct address_space *mapping,
+                                loff_t lstart, loff_t lend)
 {
         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
+        pgoff_t end;
         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
         struct pagevec pvec;
         pgoff_t next;
@@ -115,13 +118,22 @@ void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
         if (mapping->nrpages == 0)
                 return;
 
+        BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
+        end = (lend >> PAGE_CACHE_SHIFT);
+
         pagevec_init(&pvec, 0);
         next = start;
-        while (pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
+        while (next <= end &&
+               pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
                 for (i = 0; i < pagevec_count(&pvec); i++) {
                         struct page *page = pvec.pages[i];
                         pgoff_t page_index = page->index;
 
+                        if (page_index > end) {
+                                next = page_index;
+                                break;
+                        }
+
                         if (page_index > next)
                                 next = page_index;
                         next++;
@@ -157,9 +169,15 @@ void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
                         next = start;
                         continue;
                 }
+                if (pvec.pages[0]->index > end) {
+                        pagevec_release(&pvec);
+                        break;
+                }
                 for (i = 0; i < pagevec_count(&pvec); i++) {
                         struct page *page = pvec.pages[i];
 
+                        if (page->index > end)
+                                break;
                         lock_page(page);
                         wait_on_page_writeback(page);
                         if (page->index > next)
@@ -171,7 +189,19 @@ void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
                 pagevec_release(&pvec);
         }
 }
+EXPORT_SYMBOL(truncate_inode_pages_range);
 
+/**
+ * truncate_inode_pages - truncate *all* the pages from an offset
+ * @mapping: mapping to truncate
+ * @lstart: offset from which to truncate
+ *
+ * Called under (and serialised by) inode->i_sem.
+ */
+void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
+{
+        truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
+}
 EXPORT_SYMBOL(truncate_inode_pages);
 
 /**