ext4: check free inode count before allocating an inode

Recently, I ecountered some corrupted filesystems in which some
groups' free inode counts were 65535, it seemed that free inode
count was overflow.  This patch teaches ext4 to check free inode
count before allocaing an inode.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 26154b81b836..fa36372f3fdf 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -697,6 +697,15 @@ got_group:
                 if (!gdp)
                         goto fail;
 
+                /*
+                 * Check free inodes count before loading bitmap.
+                 */
+                if (ext4_free_inodes_count(sb, gdp) == 0) {
+                        if (++group == ngroups)
+                                group = 0;
+                        continue;
+                }
+
                 brelse(inode_bitmap_bh);
                 inode_bitmap_bh = ext4_read_inode_bitmap(sb, group);
                 if (!inode_bitmap_bh)