1 files changed, 38 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index f25a9092b946..a389820d158b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2354,7 +2354,7 @@ int end_extent_writepage(struct page *page, int err, u64 start, u64 end)
 {
         int uptodate = (err == 0);
         struct extent_io_tree *tree;
-        int ret;
+        int ret = 0;
 
         tree = &BTRFS_I(page->mapping->host)->io_tree;
 
@@ -5068,6 +5068,43 @@ void read_extent_buffer(struct extent_buffer *eb, void *dstv,
         }
 }
 
+int read_extent_buffer_to_user(struct extent_buffer *eb, void __user *dstv,
+                        unsigned long start,
+                        unsigned long len)
+{
+        size_t cur;
+        size_t offset;
+        struct page *page;
+        char *kaddr;
+        char __user *dst = (char __user *)dstv;
+        size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+        unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+        int ret = 0;
+
+        WARN_ON(start > eb->len);
+        WARN_ON(start + len > eb->start + eb->len);
+
+        offset = (start_offset + start) & (PAGE_CACHE_SIZE - 1);
+
+        while (len > 0) {
+                page = extent_buffer_page(eb, i);
+
+                cur = min(len, (PAGE_CACHE_SIZE - offset));
+                kaddr = page_address(page);
+                if (copy_to_user(dst, kaddr + offset, cur)) {
+                        ret = -EFAULT;
+                        break;
+                }
+
+                dst += cur;
+                len -= cur;
+                offset = 0;
+                i++;
+        }
+
+        return ret;
+}
+
 int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
                                unsigned long min_len, char **map,
                                unsigned long *map_start,