From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:50588 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726791AbfFXFxA (ORCPT ); Mon, 24 Jun 2019 01:53:00 -0400 From: Christoph Hellwig Subject: [PATCH 01/12] list.h: add a list_pop helper Date: Mon, 24 Jun 2019 07:52:42 +0200 Message-Id: <20190624055253.31183-2-hch@lst.de> In-Reply-To: <20190624055253.31183-1-hch@lst.de> References: <20190624055253.31183-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J . Wong" Cc: Damien Le Moal , Andreas Gruenbacher , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org We have a very common pattern where we want to delete the first entry from a list and return it as the properly typed container structure. Add a list_pop helper to implement this behavior. Signed-off-by: Christoph Hellwig --- include/linux/list.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/include/linux/list.h b/include/linux/list.h index e951228db4b2..e07a5f54cc9d 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -500,6 +500,28 @@ static inline void list_splice_tail_init(struct list_head *list, pos__ != head__ ? list_entry(pos__, type, member) : NULL; \ }) +/** + * list_pop - delete the first entry from a list and return it + * @list: the list to take the element from. + * @type: the type of the struct this is embedded in. + * @member: the name of the list_head within the struct. + * + * Note that if the list is empty, it returns NULL. + */ +#define list_pop(list, type, member) \ +({ \ + struct list_head *head__ = (list); \ + struct list_head *pos__ = READ_ONCE(head__->next); \ + type *entry__ = NULL; \ + \ + if (pos__ != head__) { \ + entry__ = list_entry(pos__, type, member); \ + list_del(pos__); \ + } \ + \ + entry__; \ +}) + /** * list_next_entry - get the next element in list * @pos: the type * to cursor -- 2.20.1