Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932390AbaJGXUS (ORCPT ); Tue, 7 Oct 2014 19:20:18 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39724 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932196AbaJGXUD (ORCPT ); Tue, 7 Oct 2014 19:20:03 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Streetman , Steven Rostedt , Peter Zijlstra , Mel Gorman , Paul Gortmaker , Thomas Gleixner , Shaohua Li , Hugh Dickins , Michal Hocko , Christian Ehrhardt , Weijie Yang , Rik van Riel , Johannes Weiner , Bob Liu , Andrew Morton , Linus Torvalds Subject: [PATCH 3.14 19/37] lib/plist: add plist_requeue Date: Tue, 7 Oct 2014 16:19:36 -0700 Message-Id: <20141007231827.653691389@linuxfoundation.org> X-Mailer: git-send-email 2.1.2 In-Reply-To: <20141007231827.043235686@linuxfoundation.org> References: <20141007231827.043235686@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dan Streetman commit a75f232ce0fe38bd01301899ecd97ffd0254316a upstream. Add plist_requeue(), which moves the specified plist_node after all other same-priority plist_nodes in the list. This is essentially an optimized plist_del() followed by plist_add(). This is needed by swap, which (with the next patch in this set) uses a plist of available swap devices. When a swap device (either a swap partition or swap file) are added to the system with swapon(), the device is added to a plist, ordered by the swap device's priority. When swap needs to allocate a page from one of the swap devices, it takes the page from the first swap device on the plist, which is the highest priority swap device. The swap device is left in the plist until all its pages are used, and then removed from the plist when it becomes full. However, as described in man 2 swapon, swap must allocate pages from swap devices with the same priority in round-robin order; to do this, on each swap page allocation, swap uses a page from the first swap device in the plist, and then calls plist_requeue() to move that swap device entry to after any other same-priority swap devices. The next swap page allocation will again use a page from the first swap device in the plist and requeue it, and so on, resulting in round-robin usage of equal-priority swap devices. Also add plist_test_requeue() test function, for use by plist_test() to test plist_requeue() function. Signed-off-by: Dan Streetman Cc: Steven Rostedt Cc: Peter Zijlstra Acked-by: Mel Gorman Cc: Paul Gortmaker Cc: Thomas Gleixner Cc: Shaohua Li Cc: Hugh Dickins Cc: Dan Streetman Cc: Michal Hocko Cc: Christian Ehrhardt Cc: Weijie Yang Cc: Rik van Riel Cc: Johannes Weiner Cc: Bob Liu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Greg Kroah-Hartman --- include/linux/plist.h | 2 + lib/plist.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 54 insertions(+) --- a/include/linux/plist.h +++ b/include/linux/plist.h @@ -141,6 +141,8 @@ static inline void plist_node_init(struc extern void plist_add(struct plist_node *node, struct plist_head *head); extern void plist_del(struct plist_node *node, struct plist_head *head); +extern void plist_requeue(struct plist_node *node, struct plist_head *head); + /** * plist_for_each - iterate over the plist * @pos: the type * to use as a loop counter --- a/lib/plist.c +++ b/lib/plist.c @@ -134,6 +134,46 @@ void plist_del(struct plist_node *node, plist_check_head(head); } +/** + * plist_requeue - Requeue @node at end of same-prio entries. + * + * This is essentially an optimized plist_del() followed by + * plist_add(). It moves an entry already in the plist to + * after any other same-priority entries. + * + * @node: &struct plist_node pointer - entry to be moved + * @head: &struct plist_head pointer - list head + */ +void plist_requeue(struct plist_node *node, struct plist_head *head) +{ + struct plist_node *iter; + struct list_head *node_next = &head->node_list; + + plist_check_head(head); + BUG_ON(plist_head_empty(head)); + BUG_ON(plist_node_empty(node)); + + if (node == plist_last(head)) + return; + + iter = plist_next(node); + + if (node->prio != iter->prio) + return; + + plist_del(node, head); + + plist_for_each_continue(iter, head) { + if (node->prio != iter->prio) { + node_next = &iter->node_list; + break; + } + } + list_add_tail(&node->node_list, node_next); + + plist_check_head(head); +} + #ifdef CONFIG_DEBUG_PI_LIST #include #include @@ -170,6 +210,14 @@ static void __init plist_test_check(int BUG_ON(prio_pos->prio_list.next != &first->prio_list); } +static void __init plist_test_requeue(struct plist_node *node) +{ + plist_requeue(node, &test_head); + + if (node != plist_last(&test_head)) + BUG_ON(node->prio == plist_next(node)->prio); +} + static int __init plist_test(void) { int nr_expect = 0, i, loop; @@ -193,6 +241,10 @@ static int __init plist_test(void) nr_expect--; } plist_test_check(nr_expect); + if (!plist_node_empty(test_node + i)) { + plist_test_requeue(test_node + i); + plist_test_check(nr_expect); + } } for (i = 0; i < ARRAY_SIZE(test_node); i++) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/