ext4: use EXT4_BAD_INO for buddy cache to avoid colliding with valid inode #

Signed-off-by: Yu Jian <yujian@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 70d1b3e64284..e41620b56e53 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2342,7 +2342,11 @@ static int ext4_mb_init_backend(struct super_block *sb)
                 ext4_msg(sb, KERN_ERR, "can't get new inode");
                 goto err_freesgi;
         }
-        sbi->s_buddy_cache->i_ino = get_next_ino();
+        /* To avoid potentially colliding with an valid on-disk inode number,
+         * use EXT4_BAD_INO for the buddy cache inode number.  This inode is
+         * not in the inode hash, so it should never be found by iget(), but
+         * this will avoid confusion if it ever shows up during debugging. */
+        sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;
         EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
         for (i = 0; i < ngroups; i++) {
                 desc = ext4_get_group_desc(sb, i, NULL);