1 files changed, 14 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1f26888825e2..6a6e13c53086 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -353,6 +353,7 @@ static noinline int compress_file_range(struct inode *inode,
         int i;
         int will_compress;
         int compress_type = root->fs_info->compress_type;
+        int redirty = 0;
 
         /* if this is a small write inside eof, kick off a defrag */
         if ((end - start + 1) < 16 * 1024 &&
@@ -415,6 +416,17 @@ again:
                 if (BTRFS_I(inode)->force_compress)
                         compress_type = BTRFS_I(inode)->force_compress;
 
+                /*
+                 * we need to call clear_page_dirty_for_io on each
+                 * page in the range.  Otherwise applications with the file
+                 * mmap'd can wander in and change the page contents while
+                 * we are compressing them.
+                 *
+                 * If the compression fails for any reason, we set the pages
+                 * dirty again later on.
+                 */
+                extent_range_clear_dirty_for_io(inode, start, end);
+                redirty = 1;
                 ret = btrfs_compress_pages(compress_type,
                                            inode->i_mapping, start,
                                            total_compressed, pages,
@@ -554,6 +566,8 @@ cleanup_and_bail_uncompressed:
                         __set_page_dirty_nobuffers(locked_page);
                         /* unlocked later on in the async handlers */
                 }
+                if (redirty)
+                        extent_range_redirty_for_io(inode, start, end);
                 add_async_extent(async_cow, start, end - start + 1,
                                  0, NULL, 0, BTRFS_COMPRESS_NONE);
                 *num_added += 1;