Re: [PATCH] trace-cmd: add trace_hash_find_reverse

[Josef Bacik]

On 02/23/2016 05:26 PM, Steven Rostedt wrote:
> On Tue, 15 Dec 2015 11:13:24 -0500
> Josef Bacik <jbacik@xxxxxx> wrote:
>
> > Sometimes we want to FIFO identical entries in the hash table, so add
> > trace_hash_find_reverse, which will cycle through the hash list in reverse.
> > This is helpful in our case where we are monitoring block request issues to
> > match with their corresponding completes, if we issue multiple times to the same
> > block we want to be able to match them with the correct completes (more or less
> > anyway).  Thanks,
> >
> > Signed-off-by: Josef Bacik <jbacik@xxxxxx>
> > ---
> >   list.h       |  5 +++++
> >   trace-hash.c | 22 ++++++++++++++++++++++
> >   2 files changed, 27 insertions(+)
> >
> > diff --git a/list.h b/list.h
> > index 9817871..93c64f5 100644
> > --- a/list.h
> > +++ b/list.h
> > @@ -79,4 +79,9 @@ static inline int list_empty(struct list_head *list)
> >   	     &(p)->field != list;					\
> >   	     p = n, n = container_of((p)->field.next, typeof(*p), field))
> >
> > +#define list_for_each_entry_reverse(p, list, field)			\
> > +	for (p = container_of((list)->prev, typeof(*p), field);		\
> > +	     &p->field != list;						\
> > +	     p = container_of((p)->field.prev, typeof(*p), field))
> > +
> >   #endif /* __LIST_H */
> > diff --git a/trace-hash.c b/trace-hash.c
> > index 5ffe61c..0dc4f73 100644
> > --- a/trace-hash.c
> > +++ b/trace-hash.c
> > @@ -94,3 +94,25 @@ trace_hash_find(struct trace_hash *hash, unsigned long long key,
> >
> >   	return NULL;
> >   }
> > +
> > +struct trace_hash_item *
> > +trace_hash_find_reverse(struct trace_hash *hash, unsigned long long key,
> > +			trace_hash_func match, void *data)
> > +{
> > +	struct trace_hash_item *item;
> > +	struct list_head *bucket;
> > +	int bucket_nr = hash->power ? key & hash->power :
> > +		key % hash->nr_buckets;
> > +
> > +	bucket = hash->buckets + bucket_nr;
> > +	list_for_each_entry_reverse(item, bucket, list) {
>
> Strange, this doesn't compile.
>
>   "struct trace_hash_item has no member named list"

Sorry I sent out the wrong version of this patch.  I don't actually need 
this anymore so you can just drop it.  Thanks,

Josef