ext4: Ensure zeroout blocks have no dirty metadata

This fixes a bug (found by Curt Wohlgemuth) in which new blocks
returned from an extent created with ext4_ext_zeroout() can have dirty
metadata still associated with them.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8fd6c567964a..91ae46098ea4 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3023,6 +3023,14 @@ out:
         return err;
 }
 
+static void unmap_underlying_metadata_blocks(struct block_device *bdev,
+                        sector_t block, int count)
+{
+        int i;
+        for (i = 0; i < count; i++)
+                unmap_underlying_metadata(bdev, block + i);
+}
+
 static int
 ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
                         ext4_lblk_t iblock, unsigned int max_blocks,
@@ -3098,6 +3106,18 @@ out:
         } else
                 allocated = ret;
         set_buffer_new(bh_result);
+        /*
+         * if we allocated more blocks than requested
+         * we need to make sure we unmap the extra block
+         * allocated. The actual needed block will get
+         * unmapped later when we find the buffer_head marked
+         * new.
+         */
+        if (allocated > max_blocks) {
+                unmap_underlying_metadata_blocks(inode->i_sb->s_bdev,
+                                        newblock + max_blocks,
+                                        allocated - max_blocks);
+        }
 map_out:
         set_buffer_mapped(bh_result);
 out1: