1 files changed, 25 insertions, 9 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index d9fc277940da..a1f2f02af724 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -457,7 +457,7 @@ static void shmem_free_pages(struct list_head *next)
         } while (next);
 }
 
-static void shmem_truncate(struct inode *inode)
+static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 {
         struct shmem_inode_info *info = SHMEM_I(inode);
         unsigned long idx;
@@ -475,18 +475,27 @@ static void shmem_truncate(struct inode *inode)
         long nr_swaps_freed = 0;
         int offset;
         int freed;
+        int punch_hole = 0;
 
         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
-        idx = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+        idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
         if (idx >= info->next_index)
                 return;
 
         spin_lock(&info->lock);
         info->flags |= SHMEM_TRUNCATE;
-        limit = info->next_index;
-        info->next_index = idx;
+        if (likely(end == (loff_t) -1)) {
+                limit = info->next_index;
+                info->next_index = idx;
+        } else {
+                limit = (end + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+                if (limit > info->next_index)
+                        limit = info->next_index;
+                punch_hole = 1;
+        }
+
         topdir = info->i_indirect;
-        if (topdir && idx <= SHMEM_NR_DIRECT) {
+        if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
                 info->i_indirect = NULL;
                 nr_pages_to_free++;
                 list_add(&topdir->lru, &pages_to_free);
@@ -573,11 +582,12 @@ static void shmem_truncate(struct inode *inode)
                         set_page_private(subdir, page_private(subdir) - freed);
                         if (offset)
                                 spin_unlock(&info->lock);
-                        BUG_ON(page_private(subdir) > offset);
+                        if (!punch_hole)
+                                BUG_ON(page_private(subdir) > offset);
                 }
                 if (offset)
                         offset = 0;
-                else if (subdir) {
+                else if (subdir && !page_private(subdir)) {
                         dir[diroff] = NULL;
                         nr_pages_to_free++;
                         list_add(&subdir->lru, &pages_to_free);
@@ -594,7 +604,7 @@ done2:
                  * Also, though shmem_getpage checks i_size before adding to
                  * cache, no recheck after: so fix the narrow window there too.
                  */
-                truncate_inode_pages(inode->i_mapping, inode->i_size);
+                truncate_inode_pages_range(inode->i_mapping, start, end);
         }
 
         spin_lock(&info->lock);
@@ -614,6 +624,11 @@ done2:
         }
 }
 
+static void shmem_truncate(struct inode *inode)
+{
+        shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
+}
+
 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 {
         struct inode *inode = dentry->d_inode;
@@ -1255,7 +1270,7 @@ out_nomem:
         return retval;
 }
 
-static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
+int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 {
         file_accessed(file);
         vma->vm_ops = &shmem_vm_ops;
@@ -2083,6 +2098,7 @@ static struct file_operations shmem_file_operations = {
 static struct inode_operations shmem_inode_operations = {
         .truncate       = shmem_truncate,
         .setattr        = shmem_notify_change,
+        .truncate_range = shmem_truncate_range,
 };
 
 static struct inode_operations shmem_dir_inode_operations = {