1 files changed, 21 insertions, 0 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2d54c822c4c3..5e17d5f22a7e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1005,6 +1005,9 @@ static int ext4_indirect_calc_metadata_amount(struct inode *inode, int blocks)
  */
 static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
 {
+        if (!blocks)
+                return 0;
+
         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
                 return ext4_ext_calc_metadata_amount(inode, blocks);
 
@@ -1559,7 +1562,25 @@ static void ext4_da_release_space(struct inode *inode, int to_free)
         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
         int total, mdb, mdb_free, release;
 
+        if (!to_free)
+                return;         /* Nothing to release, exit */
+
         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+
+        if (!EXT4_I(inode)->i_reserved_data_blocks) {
+                /*
+                 * if there is no reserved blocks, but we try to free some
+                 * then the counter is messed up somewhere.
+                 * but since this function is called from invalidate
+                 * page, it's harmless to return without any action
+                 */
+                printk(KERN_INFO "ext4 delalloc try to release %d reserved "
+                            "blocks for inode %lu, but there is no reserved "
+                            "data blocks\n", to_free, inode->i_ino);
+                spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+                return;
+        }
+
         /* recalculate the number of metablocks still need to be reserved */
         total = EXT4_I(inode)->i_reserved_data_blocks - to_free;
         mdb = ext4_calc_metadata_amount(inode, total);