1 files changed, 29 insertions, 0 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index 3a29a6180212..e13f22efaad7 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -304,6 +304,11 @@ EXPORT_SYMBOL(truncate_inode_pages_range);
  * @lstart: offset from which to truncate
  *
  * Called under (and serialised by) inode->i_mutex.
+ *
+ * Note: When this function returns, there can be a page in the process of
+ * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
+ * mapping->nrpages can be non-zero when this function returns even after
+ * truncation of the whole mapping.
  */
 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 {
@@ -603,3 +608,27 @@ int vmtruncate(struct inode *inode, loff_t offset)
         return 0;
 }
 EXPORT_SYMBOL(vmtruncate);
+
+int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
+{
+        struct address_space *mapping = inode->i_mapping;
+
+        /*
+         * If the underlying filesystem is not going to provide
+         * a way to truncate a range of blocks (punch a hole) -
+         * we should return failure right now.
+         */
+        if (!inode->i_op->truncate_range)
+                return -ENOSYS;
+
+        mutex_lock(&inode->i_mutex);
+        down_write(&inode->i_alloc_sem);
+        unmap_mapping_range(mapping, offset, (end - offset), 1);
+        inode->i_op->truncate_range(inode, offset, end);
+        /* unmap again to remove racily COWed private pages */
+        unmap_mapping_range(mapping, offset, (end - offset), 1);
+        up_write(&inode->i_alloc_sem);
+        mutex_unlock(&inode->i_mutex);
+
+        return 0;
+}