| Message ID | 1438009443-55317-5-git-send-email-andriy.shevchenko@linux.intel.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Mon, 27 Jul 2015, Andy Shevchenko wrote: > klist_prev() gets the previous element in the list. It is useful to traverse > through the list in reverse order, for example, to provide LIFO (last in first > out) variant of access. > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > include/linux/klist.h | 1 + > lib/klist.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 42 insertions(+) Applied, thanks. Pull request to follow. > diff --git a/include/linux/klist.h b/include/linux/klist.h > index 61e5b72..953f283 100644 > --- a/include/linux/klist.h > +++ b/include/linux/klist.h > @@ -63,6 +63,7 @@ extern void klist_iter_init(struct klist *k, struct klist_iter *i); > extern void klist_iter_init_node(struct klist *k, struct klist_iter *i, > struct klist_node *n); > extern void klist_iter_exit(struct klist_iter *i); > +extern struct klist_node *klist_prev(struct klist_iter *i); > extern struct klist_node *klist_next(struct klist_iter *i); > > #endif > diff --git a/lib/klist.c b/lib/klist.c > index 89b485a..d74cf7a 100644 > --- a/lib/klist.c > +++ b/lib/klist.c > @@ -324,6 +324,47 @@ static struct klist_node *to_klist_node(struct list_head *n) > } > > /** > + * klist_prev - Ante up prev node in list. > + * @i: Iterator structure. > + * > + * First grab list lock. Decrement the reference count of the previous > + * node, if there was one. Grab the prev node, increment its reference > + * count, drop the lock, and return that prev node. > + */ > +struct klist_node *klist_prev(struct klist_iter *i) > +{ > + void (*put)(struct klist_node *) = i->i_klist->put; > + struct klist_node *last = i->i_cur; > + struct klist_node *prev; > + > + spin_lock(&i->i_klist->k_lock); > + > + if (last) { > + prev = to_klist_node(last->n_node.prev); > + if (!klist_dec_and_del(last)) > + put = NULL; > + } else > + prev = to_klist_node(i->i_klist->k_list.prev); > + > + i->i_cur = NULL; > + while (prev != to_klist_node(&i->i_klist->k_list)) { > + if (likely(!knode_dead(prev))) { > + kref_get(&prev->n_ref); > + i->i_cur = prev; > + break; > + } > + prev = to_klist_node(prev->n_node.prev); > + } > + > + spin_unlock(&i->i_klist->k_lock); > + > + if (put && last) > + put(last); > + return i->i_cur; > +} > +EXPORT_SYMBOL_GPL(klist_prev); > + > +/** > * klist_next - Ante up next node in list. > * @i: Iterator structure. > *
diff --git a/include/linux/klist.h b/include/linux/klist.h index 61e5b72..953f283 100644 --- a/include/linux/klist.h +++ b/include/linux/klist.h @@ -63,6 +63,7 @@ extern void klist_iter_init(struct klist *k, struct klist_iter *i); extern void klist_iter_init_node(struct klist *k, struct klist_iter *i, struct klist_node *n); extern void klist_iter_exit(struct klist_iter *i); +extern struct klist_node *klist_prev(struct klist_iter *i); extern struct klist_node *klist_next(struct klist_iter *i); #endif diff --git a/lib/klist.c b/lib/klist.c index 89b485a..d74cf7a 100644 --- a/lib/klist.c +++ b/lib/klist.c @@ -324,6 +324,47 @@ static struct klist_node *to_klist_node(struct list_head *n) } /** + * klist_prev - Ante up prev node in list. + * @i: Iterator structure. + * + * First grab list lock. Decrement the reference count of the previous + * node, if there was one. Grab the prev node, increment its reference + * count, drop the lock, and return that prev node. + */ +struct klist_node *klist_prev(struct klist_iter *i) +{ + void (*put)(struct klist_node *) = i->i_klist->put; + struct klist_node *last = i->i_cur; + struct klist_node *prev; + + spin_lock(&i->i_klist->k_lock); + + if (last) { + prev = to_klist_node(last->n_node.prev); + if (!klist_dec_and_del(last)) + put = NULL; + } else + prev = to_klist_node(i->i_klist->k_list.prev); + + i->i_cur = NULL; + while (prev != to_klist_node(&i->i_klist->k_list)) { + if (likely(!knode_dead(prev))) { + kref_get(&prev->n_ref); + i->i_cur = prev; + break; + } + prev = to_klist_node(prev->n_node.prev); + } + + spin_unlock(&i->i_klist->k_lock); + + if (put && last) + put(last); + return i->i_cur; +} +EXPORT_SYMBOL_GPL(klist_prev); + +/** * klist_next - Ante up next node in list. * @i: Iterator structure. *