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Patch "fput: turn "list_head delayed_fput_list" into llist_head" has been added to the 3.10-stable tree

PATCH [email protected] 1 participant 1 message Jun 29, 2015

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This is a note to let you know that I've just added the patch titled

fput: turn "list_head delayed_fput_list" into llist_head

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fput-turn-list_head-delayed_fput_list-into-llist_head.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 4f5e65a1cc90bbb15b9f6cdc362922af1bcc155a Mon Sep 17 00:00:00 2001

From: Oleg Nesterov <[email protected]>
Date: Mon, 8 Jul 2013 14:24:16 -0700
Subject: fput: turn "list_head delayed_fput_list" into llist_head

From: Oleg Nesterov <[email protected]>

commit 4f5e65a1cc90bbb15b9f6cdc362922af1bcc155a upstream.

fput() and delayed_fput() can use llist and avoid the locking.

This is unlikely path, it is not that this change can improve the performance, but this way the code looks simpler.

Signed-off-by Oleg Nesterov <[email protected]>
Suggested-by Andrew Morton <[email protected]>
Cc Al Viro <[email protected]>
Cc Andrey Vagin <[email protected]>
Cc "Eric W. Biederman" <[email protected]>
Cc David Howells <[email protected]>
Cc Huang Ying <[email protected]>
Cc Peter Zijlstra <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Al Viro <[email protected]>
Signed-off-by Wang Kai <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/file_table.c    |   25 ++++++++++---------------
 include/linux/fs.h |    2 ++
 2 files changed, 12 insertions(+), 15 deletions(-)
fs/file_table.c +10 -15
@@ -265,18 +265,15 @@ static void __fput(struct file *file)
 	mntput(mnt);
 }
 
-static DEFINE_SPINLOCK(delayed_fput_lock);
-static LIST_HEAD(delayed_fput_list);
+static LLIST_HEAD(delayed_fput_list);
 static void delayed_fput(struct work_struct *unused)
 {
-	LIST_HEAD(head);
-	spin_lock_irq(&delayed_fput_lock);
-	list_splice_init(&delayed_fput_list, &head);
-	spin_unlock_irq(&delayed_fput_lock);
-	while (!list_empty(&head)) {
-		struct file *f = list_first_entry(&head, struct file, f_u.fu_list);
-		list_del_init(&f->f_u.fu_list);
-		__fput(f);
+	struct llist_node *node = llist_del_all(&delayed_fput_list);
+	struct llist_node *next;
+
+	for (; node; node = next) {
+		next = llist_next(node);
+		__fput(llist_entry(node, struct file, f_u.fu_llist));
 	}
 }
 

@@ -306,7 +303,6 @@ void fput(struct file *file)
 {
 	if (atomic_long_dec_and_test(&file->f_count)) {
 		struct task_struct *task = current;
-		unsigned long flags;
 
 		file_sb_list_del(file);
 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {

@@ -314,10 +310,9 @@ void fput(struct file *file)
 			if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
 				return;
 		}
-		spin_lock_irqsave(&delayed_fput_lock, flags);
-		list_add(&file->f_u.fu_list, &delayed_fput_list);
-		schedule_work(&delayed_fput_work);
-		spin_unlock_irqrestore(&delayed_fput_lock, flags);
+
+		if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
+			schedule_work(&delayed_fput_work);
 	}
 }
include/linux/fs.h +2 -0
@@ -10,6 +10,7 @@
 #include <linux/stat.h>
 #include <linux/cache.h>
 #include <linux/list.h>
+#include <linux/llist.h>
 #include <linux/radix-tree.h>
 #include <linux/rbtree.h>
 #include <linux/init.h>

@@ -767,6 +768,7 @@ struct file {
 	 */
 	union {
 		struct list_head	fu_list;
+		struct llist_node	fu_llist;
 		struct rcu_head 	fu_rcuhead;
 	} f_u;
 	struct path		f_path;

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/fput-turn-list_head-delayed_fput_list-into-llist_head.patch