1 files changed, 25 insertions, 1 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e91f978c7f12..2a9ffd528dd1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1149,6 +1149,7 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
         int retval;
 
         clear_buffer_mapped(bh);
+        clear_buffer_unwritten(bh);
 
         /*
          * Try to see if we can get  the block without requesting
@@ -1179,6 +1180,18 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
                 return retval;
 
         /*
+         * When we call get_blocks without the create flag, the
+         * BH_Unwritten flag could have gotten set if the blocks
+         * requested were part of a uninitialized extent.  We need to
+         * clear this flag now that we are committed to convert all or
+         * part of the uninitialized extent to be an initialized
+         * extent.  This is because we need to avoid the combination
+         * of BH_Unwritten and BH_Mapped flags being simultaneously
+         * set on the buffer_head.
+         */
+        clear_buffer_unwritten(bh);
+
+        /*
          * New blocks allocate and/or writing to uninitialized extent
          * will possibly result in updating i_data, so we take
          * the write lock of i_data_sem, and call get_blocks()
@@ -2297,6 +2310,10 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                                   struct buffer_head *bh_result, int create)
 {
         int ret = 0;
+        sector_t invalid_block = ~((sector_t) 0xffff);
+
+        if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
+                invalid_block = ~0;
 
         BUG_ON(create == 0);
         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
@@ -2318,11 +2335,18 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                         /* not enough space to reserve */
                         return ret;
 
-                map_bh(bh_result, inode->i_sb, 0);
+                map_bh(bh_result, inode->i_sb, invalid_block);
                 set_buffer_new(bh_result);
                 set_buffer_delay(bh_result);
         } else if (ret > 0) {
                 bh_result->b_size = (ret << inode->i_blkbits);
+                /*
+                 * With sub-block writes into unwritten extents
+                 * we also need to mark the buffer as new so that
+                 * the unwritten parts of the buffer gets correctly zeroed.
+                 */
+                if (buffer_unwritten(bh_result))
+                        set_buffer_new(bh_result);
                 ret = 0;
         }