Christoph Hellwig [off-list ref] wrote:

+static inline int hugetlbfs_inc_free_inodes(struct hugetlbfs_sb_info *sbinfo)
 +{
 +	if (sbinfo->free_inodes >= 0) {
 +		spin_lock(&sbinfo->stat_lock);
 +		if (unlikely(!sbinfo->free_inodes)) {
 +			spin_unlock(&sbinfo->stat_lock);
 +			return 0;
 +		}
 +		sbinfo->free_inodes--;
 +		spin_unlock(&sbinfo->stat_lock);
 +	}
 +
 +	return 1;
 +}
 +
 +static void hugetlbfs_dec_free_inodes(struct hugetlbfs_sb_info *sbinfo)
 +{
 +	if (sbinfo->free_inodes >= 0) {
 +		spin_lock(&sbinfo->stat_lock);
 +		sbinfo->free_inodes++;
 +		spin_unlock(&sbinfo->stat_lock);
 +	}
 +}
 +

These functions seem to be called from the right places, but the naming is
most confusing.

The test for the current value of sbinfo->free_inodes in
hugetlbfs_dec_free_inodes() looks racy and the logic simply escapes me. 
Does anyone remember why we have special-case handling in there for
(sbinfo->free_inodes < 0)?

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