From patchwork Tue Jun 29 02:35:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12348975 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E146EC11F67 for ; Tue, 29 Jun 2021 02:36:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 90E7D61A2B for ; Tue, 29 Jun 2021 02:36:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 90E7D61A2B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E67018D00A9; Mon, 28 Jun 2021 22:36:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E3D048D008F; Mon, 28 Jun 2021 22:36:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D04C08D00A9; Mon, 28 Jun 2021 22:36:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0130.hostedemail.com [216.40.44.130]) by kanga.kvack.org (Postfix) with ESMTP id A67218D008F for ; Mon, 28 Jun 2021 22:36:01 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 9D2B98249980 for ; Tue, 29 Jun 2021 02:36:01 +0000 (UTC) X-FDA: 78305196522.02.7242C1E Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP id 394F0E00025C for ; Tue, 29 Jun 2021 02:36:01 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2D11161D06; Tue, 29 Jun 2021 02:36:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624934160; bh=XjojDIoV2fEnI6SdKXAhIrGwsMifawnqrloqXU5sTXI=; h=Date:From:To:Subject:In-Reply-To:From; b=wE7VN6gKXXd9JLJwvlsXr4BN/gjxE5EtfJDgpZocJb1CNTU3bp+f47FaJRfxSlpoU zXbMqLJBSKdWqWMn3H56Cl9O3epKkwrbuqz79VZaMbPUApFlAmDljVM+spTr0vMhyB WMfFP1PN4D1cfnYU8pF+RAkwa2ULtOq2nwP2eGSY= Date: Mon, 28 Jun 2021 19:35:59 -0700 From: Andrew Morton To: akpm@linux-foundation.org, axboe@kernel.dk, dchinner@redhat.com, dennis@kernel.org, guro@fb.com, jack@suse.com, jack@suse.cz, linux-mm@kvack.org, mm-commits@vger.kernel.org, tj@kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk Subject: [patch 052/192] writeback, cgroup: support switching multiple inodes at once Message-ID: <20210629023559.AUtAARde5%akpm@linux-foundation.org> In-Reply-To: <20210628193256.008961950a714730751c1423@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 394F0E00025C X-Stat-Signature: 4fna71wpq8fochb8t3nw6fwjgfed9tgu Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=wE7VN6gK; dmarc=none; spf=pass (imf05.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-HE-Tag: 1624934161-226777 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Roman Gushchin Subject: writeback, cgroup: support switching multiple inodes at once Currently only a single inode can be switched to another writeback structure at once. That means to switch an inode a separate inode_switch_wbs_context structure must be allocated, and a separate rcu callback and work must be scheduled. It's fine for the existing ad-hoc switching, which is not happening that often, but sub-optimal for massive switching required in order to release a writeback structure. To prepare for it, let's add a support for switching multiple inodes at once. Instead of containing a single inode pointer, inode_switch_wbs_context will contain a NULL-terminated array of inode pointers. inode_do_switch_wbs() will be called for each inode. To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's list_locks will be acquired and released only once altogether for all inodes. wb_wakeup() will be also be called only once. Instead of calling wb_put(old_wb) after each successful switch, wb_put_many() is introduced and used. Link: https://lkml.kernel.org/r/20210608230225.2078447-8-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Reviewed-by: Jan Kara Acked-by: Dennis Zhou Cc: Alexander Viro Cc: Dave Chinner Cc: Jan Kara Cc: Jens Axboe Signed-off-by: Andrew Morton --- fs/fs-writeback.c | 106 +++++++++++++++++------------ include/linux/backing-dev-defs.h | 18 ++++ 2 files changed, 80 insertions(+), 44 deletions(-) --- a/fs/fs-writeback.c~writeback-cgroup-support-switching-multiple-inodes-at-once +++ a/fs/fs-writeback.c @@ -335,10 +335,18 @@ static struct bdi_writeback *inode_to_wb } struct inode_switch_wbs_context { - struct inode *inode; - struct bdi_writeback *new_wb; - struct rcu_work work; + + /* + * Multiple inodes can be switched at once. The switching procedure + * consists of two parts, separated by a RCU grace period. To make + * sure that the second part is executed for each inode gone through + * the first part, all inode pointers are placed into a NULL-terminated + * array embedded into struct inode_switch_wbs_context. Otherwise + * an inode could be left in a non-consistent state. + */ + struct bdi_writeback *new_wb; + struct inode *inodes[]; }; static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) @@ -351,39 +359,15 @@ static void bdi_up_write_wb_switch_rwsem up_write(&bdi->wb_switch_rwsem); } -static void inode_do_switch_wbs(struct inode *inode, +static bool inode_do_switch_wbs(struct inode *inode, + struct bdi_writeback *old_wb, struct bdi_writeback *new_wb) { - struct backing_dev_info *bdi = inode_to_bdi(inode); struct address_space *mapping = inode->i_mapping; - struct bdi_writeback *old_wb = inode->i_wb; XA_STATE(xas, &mapping->i_pages, 0); struct page *page; bool switched = false; - /* - * If @inode switches cgwb membership while sync_inodes_sb() is - * being issued, sync_inodes_sb() might miss it. Synchronize. - */ - down_read(&bdi->wb_switch_rwsem); - - /* - * By the time control reaches here, RCU grace period has passed - * since I_WB_SWITCH assertion and all wb stat update transactions - * between unlocked_inode_to_wb_begin/end() are guaranteed to be - * synchronizing against the i_pages lock. - * - * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock - * gives us exclusion against all wb related operations on @inode - * including IO list manipulations and stat updates. - */ - if (old_wb < new_wb) { - spin_lock(&old_wb->list_lock); - spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); - } else { - spin_lock(&new_wb->list_lock); - spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); - } spin_lock(&inode->i_lock); xa_lock_irq(&mapping->i_pages); @@ -458,25 +442,63 @@ skip_switch: xa_unlock_irq(&mapping->i_pages); spin_unlock(&inode->i_lock); - spin_unlock(&new_wb->list_lock); - spin_unlock(&old_wb->list_lock); - - up_read(&bdi->wb_switch_rwsem); - if (switched) { - wb_wakeup(new_wb); - wb_put(old_wb); - } + return switched; } static void inode_switch_wbs_work_fn(struct work_struct *work) { struct inode_switch_wbs_context *isw = container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); + struct backing_dev_info *bdi = inode_to_bdi(isw->inodes[0]); + struct bdi_writeback *old_wb = isw->inodes[0]->i_wb; + struct bdi_writeback *new_wb = isw->new_wb; + unsigned long nr_switched = 0; + struct inode **inodep; + + /* + * If @inode switches cgwb membership while sync_inodes_sb() is + * being issued, sync_inodes_sb() might miss it. Synchronize. + */ + down_read(&bdi->wb_switch_rwsem); + + /* + * By the time control reaches here, RCU grace period has passed + * since I_WB_SWITCH assertion and all wb stat update transactions + * between unlocked_inode_to_wb_begin/end() are guaranteed to be + * synchronizing against the i_pages lock. + * + * Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock + * gives us exclusion against all wb related operations on @inode + * including IO list manipulations and stat updates. + */ + if (old_wb < new_wb) { + spin_lock(&old_wb->list_lock); + spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); + } else { + spin_lock(&new_wb->list_lock); + spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); + } + + for (inodep = isw->inodes; *inodep; inodep++) { + WARN_ON_ONCE((*inodep)->i_wb != old_wb); + if (inode_do_switch_wbs(*inodep, old_wb, new_wb)) + nr_switched++; + } + + spin_unlock(&new_wb->list_lock); + spin_unlock(&old_wb->list_lock); + + up_read(&bdi->wb_switch_rwsem); + + if (nr_switched) { + wb_wakeup(new_wb); + wb_put_many(old_wb, nr_switched); + } - inode_do_switch_wbs(isw->inode, isw->new_wb); - wb_put(isw->new_wb); - iput(isw->inode); + for (inodep = isw->inodes; *inodep; inodep++) + iput(*inodep); + wb_put(new_wb); kfree(isw); atomic_dec(&isw_nr_in_flight); } @@ -503,7 +525,7 @@ static void inode_switch_wbs(struct inod if (atomic_read(&isw_nr_in_flight) > WB_FRN_MAX_IN_FLIGHT) return; - isw = kzalloc(sizeof(*isw), GFP_ATOMIC); + isw = kzalloc(sizeof(*isw) + 2 * sizeof(struct inode *), GFP_ATOMIC); if (!isw) return; @@ -530,7 +552,7 @@ static void inode_switch_wbs(struct inod __iget(inode); spin_unlock(&inode->i_lock); - isw->inode = inode; + isw->inodes[0] = inode; /* * In addition to synchronizing among switchers, I_WB_SWITCH tells --- a/include/linux/backing-dev-defs.h~writeback-cgroup-support-switching-multiple-inodes-at-once +++ a/include/linux/backing-dev-defs.h @@ -240,8 +240,9 @@ static inline void wb_get(struct bdi_wri /** * wb_put - decrement a wb's refcount * @wb: bdi_writeback to put + * @nr: number of references to put */ -static inline void wb_put(struct bdi_writeback *wb) +static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr) { if (WARN_ON_ONCE(!wb->bdi)) { /* @@ -252,7 +253,16 @@ static inline void wb_put(struct bdi_wri } if (wb != &wb->bdi->wb) - percpu_ref_put(&wb->refcnt); + percpu_ref_put_many(&wb->refcnt, nr); +} + +/** + * wb_put - decrement a wb's refcount + * @wb: bdi_writeback to put + */ +static inline void wb_put(struct bdi_writeback *wb) +{ + wb_put_many(wb, 1); } /** @@ -281,6 +291,10 @@ static inline void wb_put(struct bdi_wri { } +static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr) +{ +} + static inline bool wb_dying(struct bdi_writeback *wb) { return false;