On Mar. 18, 2009, 23:03 +0200, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> On Wed, Mar 18, 2009 at 10:40:41PM +0200, Benny Halevy wrote:
>> On Mar. 18, 2009, 22:28 +0200, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
>>> static inline void
>>> put_nfs4_file(struct nfs4_file *fi)
>>> {
>>> - kref_put(&fi->fi_ref, free_nfs4_file);
>> missing spin_lock(&recall_lock);?
>>
>>
>>> + if (atomic_dec_and_lock(&fi->fi_ref, &recall_lock)) {
>>> + list_del(&fi->fi_hash);
>>> + spin_unlock(&recall_lock);
>>> + iput(fi->fi_inode);
>>> + kmem_cache_free(file_slab, fi);
>>> + }
>> } else {
>> spin_unlock(&recall_lock);
>> }
>>
>> or am I missing something?
>
> From include/linux/spinlock.h:
>
> /**
> * atomic_dec_and_lock - lock on reaching reference count zero
> * @atomic: the atomic counter
> * @lock: the spinlock in question
> *
> * Decrements @atomic by 1. If the result is 0, returns true and locks
> * @lock. Returns false for all other cases.
> */
>
> So it's useful for cases such as this, when a reference-counted object
> is reachable from some data structure visible to others, and you want to
> remove it from that structure on dropping the last reference (as opposed
> to keeping one reference for the structure itself, and requiring the
> object to be explicitly removed).
>
> (Unless I'm missing something else.)
My bad. I did miss that.
Patch looks good to me now.
Benny
>
> --b.
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