f2fs: don't let the orphan inode counter underflow

Accounting errors from buggy code calling the acquire/release/remove
orphan inode interfaces can cause n_orphans to underflow, which will
then cause acquire_orphan_inode() to return -ENOSPC on the next
operation.  This commit guards against that condition.

Signed-off-by: Russ Knize <rknize@motorola.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index bb312201ca95..ca3944240db5 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -206,6 +206,7 @@ int acquire_orphan_inode(struct f2fs_sb_info *sbi)
 void release_orphan_inode(struct f2fs_sb_info *sbi)
 {
         mutex_lock(&sbi->orphan_inode_mutex);
+        BUG_ON(sbi->n_orphans == 0);
         sbi->n_orphans--;
         mutex_unlock(&sbi->orphan_inode_mutex);
 }
@@ -253,6 +254,7 @@ void remove_orphan_inode(struct f2fs_sb_info *sbi, nid_t ino)
                 if (orphan->ino == ino) {
                         list_del(&orphan->list);
                         kmem_cache_free(orphan_entry_slab, orphan);
+                        BUG_ON(sbi->n_orphans == 0);
                         sbi->n_orphans--;
                         break;
                 }