From patchwork Tue Mar 17 16:24:46 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Theodore Ts'o X-Patchwork-Id: 6032931 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 90A11BF90F for ; Tue, 17 Mar 2015 16:25:00 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 76E112049D for ; Tue, 17 Mar 2015 16:24:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59355204A2 for ; Tue, 17 Mar 2015 16:24:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754455AbbCQQYz (ORCPT ); Tue, 17 Mar 2015 12:24:55 -0400 Received: from imap.thunk.org ([74.207.234.97]:45058 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754361AbbCQQYy (ORCPT ); Tue, 17 Mar 2015 12:24:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=Message-Id:Date:Subject:Cc:To:From; bh=1PUF8MuH4uRs6e0Wu17ugqft07u3kIxe43GGiAHpYKg=; b=MjhqYbj+vcFANV8SDt0Aa/8VIe7cpx2PjueYDWxaCxyJPcjLAOxOzdZ8WRGTJ0pJ+dMsckHUXGKnmTzXkSkrFKlOdIaNKoWAQJ5bZLprLilM4+yjjlkTE2+vqwMvuYRCEYLe401E/ZNkPOBWbfKWiPgAV8JQFieiP9sPJmYS5ro=; Received: from root (helo=closure.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.80) (envelope-from ) id 1YXuIW-0003iF-O6; Tue, 17 Mar 2015 16:24:52 +0000 Received: by closure.thunk.org (Postfix, from userid 15806) id 69C5E5803E6; Tue, 17 Mar 2015 12:24:52 -0400 (EDT) From: Theodore Ts'o To: Linux Filesystem Development List Cc: jack@suse.cz, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, Theodore Ts'o Subject: [PATCH-v3 1/2] fs: make sure the timestamps for lazytime inodes eventually get written Date: Tue, 17 Mar 2015 12:24:46 -0400 Message-Id: <1426609487-18744-1-git-send-email-tytso@mit.edu> X-Mailer: git-send-email 2.3.0 X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID,T_RP_MATCHES_RCVD,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Jan Kara pointed out that if there is an inode which is constantly getting dirtied with I_DIRTY_PAGES, an inode with an updated timestamp will never be written since inode->dirtied_when is constantly getting updated. We fix this by adding an extra field to the inode, dirtied_time_when, so inodes with a stale dirtytime can get detected and handled. In addition, if we have a dirtytime inode caused by an atime update, and there is no write activity on the file system, we need to have a secondary system to make sure these inodes get written out. We do this by setting up a second delayed work structure which wakes up the CPU much more rarely compared to writeback_expire_centisecs. Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara --- fs/fs-writeback.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++------- include/linux/fs.h | 1 + 2 files changed, 73 insertions(+), 10 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index e907052..2cfcd74 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -53,6 +53,18 @@ struct wb_writeback_work { struct completion *done; /* set if the caller waits */ }; +/* + * If an inode is constantly having its pages dirtied, but then the + * updates stop dirtytime_expire_interval seconds in the past, it's + * possible for the worst case time between when an inode has its + * timestamps updated and when they finally get written out to be two + * dirtytime_expire_intervals. We set the default to 12 hours (in + * seconds), which means most of the time inodes will have their + * timestamps written to disk after 12 hours, but in the worst case a + * few inodes might not their timestamps updated for 24 hours. + */ +unsigned int dirtytime_expire_interval = 12 * 60 * 60; + /** * writeback_in_progress - determine whether there is writeback in progress * @bdi: the device's backing_dev_info structure. @@ -275,8 +287,8 @@ static int move_expired_inodes(struct list_head *delaying_queue, if ((flags & EXPIRE_DIRTY_ATIME) == 0) older_than_this = work->older_than_this; - else if ((work->reason == WB_REASON_SYNC) == 0) { - expire_time = jiffies - (HZ * 86400); + else if (!work->for_sync) { + expire_time = jiffies - (dirtytime_expire_interval * HZ); older_than_this = &expire_time; } while (!list_empty(delaying_queue)) { @@ -458,6 +470,7 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, */ redirty_tail(inode, wb); } else if (inode->i_state & I_DIRTY_TIME) { + inode->dirtied_when = jiffies; list_move(&inode->i_wb_list, &wb->b_dirty_time); } else { /* The inode is clean. Remove from writeback lists. */ @@ -505,12 +518,17 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc) spin_lock(&inode->i_lock); dirty = inode->i_state & I_DIRTY; - if (((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) && - (inode->i_state & I_DIRTY_TIME)) || - (inode->i_state & I_DIRTY_TIME_EXPIRED)) { - dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED; - trace_writeback_lazytime(inode); - } + if (inode->i_state & I_DIRTY_TIME) { + if ((dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) || + unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) || + unlikely(time_after(jiffies, + (inode->dirtied_time_when + + dirtytime_expire_interval * HZ)))) { + dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED; + trace_writeback_lazytime(inode); + } + } else + inode->i_state &= ~I_DIRTY_TIME_EXPIRED; inode->i_state &= ~dirty; /* @@ -1131,6 +1149,45 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason) rcu_read_unlock(); } +/* + * Wake up bdi's periodically to make sure dirtytime inodes gets + * written back periodically. We deliberately do *not* check the + * b_dirtytime list in wb_has_dirty_io(), since this would cause the + * kernel to be constantly waking up once there are any dirtytime + * inodes on the system. So instead we define a separate delayed work + * function which gets called much more rarely. (By default, only + * once every 12 hours.) + * + * If there is any other write activity going on in the file system, + * this function won't be necessary. But if the only thing that has + * happened on the file system is a dirtytime inode caused by an atime + * update, we need this infrastructure below to make sure that inode + * eventually gets pushed out to disk. + */ +static void wakeup_dirtytime_writeback(struct work_struct *w); +static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback); + +static void wakeup_dirtytime_writeback(struct work_struct *w) +{ + struct backing_dev_info *bdi; + + rcu_read_lock(); + list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { + if (list_empty(&bdi->wb.b_dirty_time)) + continue; + bdi_wakeup_thread(bdi); + } + rcu_read_unlock(); + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); +} + +static int __init start_dirtytime_writeback(void) +{ + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); + return 0; +} +__initcall(start_dirtytime_writeback); + static noinline void block_dump___mark_inode_dirty(struct inode *inode) { if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) { @@ -1269,8 +1326,13 @@ void __mark_inode_dirty(struct inode *inode, int flags) } inode->dirtied_when = jiffies; - list_move(&inode->i_wb_list, dirtytime ? - &bdi->wb.b_dirty_time : &bdi->wb.b_dirty); + if (dirtytime) + inode->dirtied_time_when = jiffies; + if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES)) + list_move(&inode->i_wb_list, &bdi->wb.b_dirty); + else + list_move(&inode->i_wb_list, + &bdi->wb.b_dirty_time); spin_unlock(&bdi->wb.list_lock); trace_writeback_dirty_inode_enqueue(inode); diff --git a/include/linux/fs.h b/include/linux/fs.h index b4d71b5..f4131e8 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -604,6 +604,7 @@ struct inode { struct mutex i_mutex; unsigned long dirtied_when; /* jiffies of first dirtying */ + unsigned long dirtied_time_when; struct hlist_node i_hash; struct list_head i_wb_list; /* backing dev IO list */