From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756021AbaIEHHw (ORCPT ); Fri, 5 Sep 2014 03:07:52 -0400 Received: from mailout1.samsung.com ([203.254.224.24]:46631 "EHLO mailout1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755901AbaIEHHu (ORCPT ); Fri, 5 Sep 2014 03:07:50 -0400 X-AuditID: cbfee61a-f79e46d00000134f-a0-540961444cba From: Chao Yu To: "'Gu Zheng'" , jaegeuk@kernel.org Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net References: <1409735782-7831-1-git-send-email-guz.fnst@cn.fujitsu.com> In-reply-to: <1409735782-7831-1-git-send-email-guz.fnst@cn.fujitsu.com> Subject: RE: [f2fs-dev] [PATCH] f2fs: use lock-less list(llist) to simplify the flush cmd management Date: Fri, 05 Sep 2014 15:07:01 +0800 Message-id: <002101cfc8d8$1963b650$4c2b22f0$@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-index: AQKbH1gJnmSzm7GNocRYWJqgiZpbuppbZHGA Content-language: zh-cn X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrBLMWRmVeSWpSXmKPExsVy+t9jAV2XRM4Qg4vHhS2etx9gtniyfhaz xaVF7haXd81hc2Dx+H9wErPHplWdbB67F3xm8vi8SS6AJYrLJiU1J7MstUjfLoEr4/fuHvaC Xo2KwyefMzUwvlfoYuTgkBAwkfje4dTFyAlkiklcuLeeDcQWEljEKNHSGtHFyAVk/2CUuHzg LgtIgk1ARWJ5x38mEFtEwEbi29xGNpA5zAIeEruOlUL0ukm8n34MrIRTwF3i44HP7CC2sECa xOM578HmswioStx5vRrM5hWwlDh9+TMLhC0o8WPyPTCbWUBLYv3O40wQtrzE5jVvmSHuVJDY cfY1I8QJRhLvt/5jhagRl9h45BbLBEahWUhGzUIyahaSUbOQtCxgZFnFKJpakFxQnJSea6hX nJhbXJqXrpecn7uJERz+z6R2MK5ssDjEKMDBqMTDu+AzR4gQa2JZcWXuIUYJDmYlEd72CM4Q Id6UxMqq1KL8+KLSnNTiQ4zSHCxK4rwHWq0DhQTSE0tSs1NTC1KLYLJMHJxSDYzOtVrTrFQC FQM6pl88vtzT9cP9XUrtLy88Y25oOdxl6SKzdicX++TCU85rPk/V8Z+3YckOFa0HE63Utoec ajAzUtod8+3Z8s0cFzasmJdlfnUC79/Pc7o2/Fqslrz8tdDa7y2n+E0ypoU/snz9in/+weB0 k49Cknu6t+mscJ5ePVE9NuZT+I8LSizFGYmGWsxFxYkAuZdz33sCAAA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gu, > -----Original Message----- > From: Gu Zheng [mailto:guz.fnst@cn.fujitsu.com] > Sent: Wednesday, September 03, 2014 5:16 PM > To: jaegeuk@kernel.org > Cc: Gu Zheng; linux-kernel@vger.kernel.org; linux-f2fs-devel@lists.sourceforge.net > Subject: [f2fs-dev] [PATCH] f2fs: use lock-less list(llist) to simplify the flush cmd management > > We use flush cmd control to collect many flush cmds, and flush them > together. In this case, we use two list to manage the flush cmds > (collect and dispatch), and one spin lock is used to protect this. > In fact, the lock-less list(llist) is very suitable to this case, > and we use simplify this routine. Good catch for finding this scenario with llist! > > Signed-off-by: Gu Zheng > --- > fs/f2fs/f2fs.h | 7 +++---- > fs/f2fs/segment.c | 31 +++++++++---------------------- > 2 files changed, 12 insertions(+), 26 deletions(-) > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index e921242..1dd861c 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -334,16 +334,15 @@ enum { > struct flush_cmd { > struct flush_cmd *next; No needed here, we can remove it. > struct completion wait; > + struct llist_node llnode; > int ret; > }; > > struct flush_cmd_control { > struct task_struct *f2fs_issue_flush; /* flush thread */ > wait_queue_head_t flush_wait_queue; /* waiting queue for wake-up */ > - struct flush_cmd *issue_list; /* list for command issue */ > - struct flush_cmd *dispatch_list; /* list for command dispatch */ > - spinlock_t issue_lock; /* for issue list lock */ > - struct flush_cmd *issue_tail; /* list tail of issue list */ > + struct llist_head issue_list; /* list for command issue */ > + struct llist_node *dispatch_list; /* list for command dispatch */ > }; > > struct f2fs_sm_info { > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 0aa337c..2db1f95 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -205,24 +205,19 @@ repeat: > if (kthread_should_stop()) > return 0; > > - spin_lock(&fcc->issue_lock); > - if (fcc->issue_list) { > - fcc->dispatch_list = fcc->issue_list; > - fcc->issue_list = fcc->issue_tail = NULL; > - } > - spin_unlock(&fcc->issue_lock); > - > - if (fcc->dispatch_list) { > + if (!llist_empty(&fcc->issue_list)) { > struct bio *bio = bio_alloc(GFP_NOIO, 0); > - struct flush_cmd *cmd, *next; > + struct flush_cmd *cmd; > int ret; > > + fcc->dispatch_list = llist_del_all(&fcc->issue_list); > + fcc->dispatch_list = llist_reverse_order(fcc->dispatch_list); > + > bio->bi_bdev = sbi->sb->s_bdev; > ret = submit_bio_wait(WRITE_FLUSH, bio); > > - for (cmd = fcc->dispatch_list; cmd; cmd = next) { > + llist_for_each_entry(cmd, fcc->dispatch_list, llnode) { Please use llist_for_each_entry_safe, Otherwise we might encounter oops as below: [18727.381582] Call Trace: [18727.381613] [] __wake_up_locked+0x1f/0x30 [18727.381626] [] complete+0x36/0x50 [18727.381645] [] issue_flush_thread+0x93/0x140 [f2fs] [18727.381658] [] ? add_wait_queue+0x50/0x50 [18727.381672] [] ? add_sit_entry+0xc0/0xc0 [f2fs] [18727.381687] [] kthread+0x9b/0xb0 [18727.381701] [] ret_from_kernel_thread+0x21/0x30 [18727.381714] [] ? flush_kthread_worker+0x80/0x80 Thanks, Yu > cmd->ret = ret; > - next = cmd->next; > complete(&cmd->wait); > } > bio_put(bio); > @@ -230,7 +225,7 @@ repeat: > } > > wait_event_interruptible(*q, > - kthread_should_stop() || fcc->issue_list); > + kthread_should_stop() || !llist_empty(&fcc->issue_list)); > goto repeat; > } > > @@ -249,17 +244,10 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi) > return blkdev_issue_flush(sbi->sb->s_bdev, GFP_KERNEL, NULL); > > init_completion(&cmd.wait); > - cmd.next = NULL; > > - spin_lock(&fcc->issue_lock); > - if (fcc->issue_list) > - fcc->issue_tail->next = &cmd; > - else > - fcc->issue_list = &cmd; > - fcc->issue_tail = &cmd; > - spin_unlock(&fcc->issue_lock); > + llist_add(&cmd.llnode, &fcc->issue_list); > > - if (!fcc->dispatch_list) > + if (fcc->dispatch_list == NULL) > wake_up(&fcc->flush_wait_queue); > > wait_for_completion(&cmd.wait); > @@ -276,7 +264,6 @@ int create_flush_cmd_control(struct f2fs_sb_info *sbi) > fcc = kzalloc(sizeof(struct flush_cmd_control), GFP_KERNEL); > if (!fcc) > return -ENOMEM; > - spin_lock_init(&fcc->issue_lock); > init_waitqueue_head(&fcc->flush_wait_queue); > SM_I(sbi)->cmd_control_info = fcc; > fcc->f2fs_issue_flush = kthread_run(issue_flush_thread, sbi, > -- > 1.7.7 > > > ------------------------------------------------------------------------------ > Slashdot TV. > Video for Nerds. Stuff that matters. > http://tv.slashdot.org/ > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel