From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 C0E09C43387 for ; Wed, 16 Jan 2019 19:12:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B4A620866 for ; Wed, 16 Jan 2019 19:12:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730395AbfAPTMr (ORCPT ); Wed, 16 Jan 2019 14:12:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:56300 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729879AbfAPTMr (ORCPT ); Wed, 16 Jan 2019 14:12:47 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 876ADAE54; Wed, 16 Jan 2019 19:12:45 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 42C65DA828; Wed, 16 Jan 2019 20:12:16 +0100 (CET) Date: Wed, 16 Jan 2019 20:12:16 +0100 From: David Sterba To: Josef Bacik Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue Message-ID: <20190116191216.GQ2900@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Josef Bacik , linux-btrfs@vger.kernel.org, kernel-team@fb.com References: <20190111152103.17001-1-josef@toxicpanda.com> <20190111152103.17001-4-josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190111152103.17001-4-josef@toxicpanda.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Jan 11, 2019 at 10:21:03AM -0500, Josef Bacik wrote: > The throttle path doesn't take cleaner_delayed_iput_mutex, which means > we could think we're done flushing iputs in the data space reservation > path when we could have a throttler doing an iput. There's no real > reason to serialize the delayed iput flushing, so instead of taking the > cleaner_delayed_iput_mutex whenever we flush the delayed iputs just > replace it with an atomic counter and a waitqueue. This removes the > short (or long depending on how big the inode is) window where we think > there are no more pending iputs when there really are some. > > Signed-off-by: Josef Bacik > --- > fs/btrfs/ctree.h | 4 +++- > fs/btrfs/disk-io.c | 5 ++--- > fs/btrfs/extent-tree.c | 13 ++++++++----- > fs/btrfs/inode.c | 21 +++++++++++++++++++++ > 4 files changed, 34 insertions(+), 9 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index dc56a4d940c3..20af5d6d81f1 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -915,7 +915,8 @@ struct btrfs_fs_info { > > spinlock_t delayed_iput_lock; > struct list_head delayed_iputs; > - struct mutex cleaner_delayed_iput_mutex; > + atomic_t nr_delayed_iputs; > + wait_queue_head_t delayed_iputs_wait; > > /* this protects tree_mod_seq_list */ > spinlock_t tree_mod_seq_lock; > @@ -3240,6 +3241,7 @@ int btrfs_orphan_cleanup(struct btrfs_root *root); > int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size); > void btrfs_add_delayed_iput(struct inode *inode); > void btrfs_run_delayed_iputs(struct btrfs_fs_info *fs_info); > +int btrfs_wait_on_delayed_iputs(struct btrfs_fs_info *fs_info); > int btrfs_prealloc_file_range(struct inode *inode, int mode, > u64 start, u64 num_bytes, u64 min_size, > loff_t actual_len, u64 *alloc_hint); > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index f40f6fdc1019..238e0113f2d3 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -1694,9 +1694,7 @@ static int cleaner_kthread(void *arg) > goto sleep; > } > > - mutex_lock(&fs_info->cleaner_delayed_iput_mutex); > btrfs_run_delayed_iputs(fs_info); > - mutex_unlock(&fs_info->cleaner_delayed_iput_mutex); > > again = btrfs_clean_one_deleted_snapshot(root); > mutex_unlock(&fs_info->cleaner_mutex); > @@ -2654,7 +2652,6 @@ int open_ctree(struct super_block *sb, > mutex_init(&fs_info->delete_unused_bgs_mutex); > mutex_init(&fs_info->reloc_mutex); > mutex_init(&fs_info->delalloc_root_mutex); > - mutex_init(&fs_info->cleaner_delayed_iput_mutex); > seqlock_init(&fs_info->profiles_lock); > > INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots); > @@ -2676,6 +2673,7 @@ int open_ctree(struct super_block *sb, > atomic_set(&fs_info->defrag_running, 0); > atomic_set(&fs_info->qgroup_op_seq, 0); > atomic_set(&fs_info->reada_works_cnt, 0); > + atomic_set(&fs_info->nr_delayed_iputs, 0); > atomic64_set(&fs_info->tree_mod_seq, 0); > fs_info->sb = sb; > fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE; > @@ -2753,6 +2751,7 @@ int open_ctree(struct super_block *sb, > init_waitqueue_head(&fs_info->transaction_wait); > init_waitqueue_head(&fs_info->transaction_blocked_wait); > init_waitqueue_head(&fs_info->async_submit_wait); > + init_waitqueue_head(&fs_info->delayed_iputs_wait); > > INIT_LIST_HEAD(&fs_info->pinned_chunks); > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 0127d272cd2a..5b6c9fc227ff 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -4280,10 +4280,14 @@ int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes) > /* > * The cleaner kthread might still be doing iput > * operations. Wait for it to finish so that > - * more space is released. > + * more space is released. We don't need to > + * explicitly run the delayed iputs here because > + * the commit_transaction would have woken up > + * the cleaner. > */ > - mutex_lock(&fs_info->cleaner_delayed_iput_mutex); > - mutex_unlock(&fs_info->cleaner_delayed_iput_mutex); > + ret = btrfs_wait_on_delayed_iputs(fs_info); > + if (ret) > + return ret; > goto again; > } else { > btrfs_end_transaction(trans); > @@ -4958,9 +4962,8 @@ static void flush_space(struct btrfs_fs_info *fs_info, > * bunch of pinned space, so make sure we run the iputs before > * we do our pinned bytes check below. > */ > - mutex_lock(&fs_info->cleaner_delayed_iput_mutex); > btrfs_run_delayed_iputs(fs_info); > - mutex_unlock(&fs_info->cleaner_delayed_iput_mutex); > + btrfs_wait_on_delayed_iputs(fs_info); > > ret = may_commit_transaction(fs_info, space_info); > break; > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 0b9f3e482cea..958e30c7c744 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -3260,6 +3260,7 @@ void btrfs_add_delayed_iput(struct inode *inode) > if (atomic_add_unless(&inode->i_count, -1, 1)) > return; > > + atomic_inc(&fs_info->nr_delayed_iputs); > spin_lock(&fs_info->delayed_iput_lock); > ASSERT(list_empty(&binode->delayed_iput)); > list_add_tail(&binode->delayed_iput, &fs_info->delayed_iputs); > @@ -3280,11 +3281,31 @@ void btrfs_run_delayed_iputs(struct btrfs_fs_info *fs_info) > list_del_init(&inode->delayed_iput); > spin_unlock(&fs_info->delayed_iput_lock); > iput(&inode->vfs_inode); > + if (atomic_dec_and_test(&fs_info->nr_delayed_iputs)) > + wake_up(&fs_info->delayed_iputs_wait); > spin_lock(&fs_info->delayed_iput_lock); > } > spin_unlock(&fs_info->delayed_iput_lock); > } > > +/** > + * btrfs_wait_on_delayed_iputs - wait on the delayed iputs to be done running > + * @fs_info - the fs_info for this fs > + * @return - EINTR if we were killed, 0 if nothing's pending > + * > + * This will wait on any delayed iputs that are currently running with KILLABLE > + * set. Once they are all done running we will return, unless we are killed in > + * which case we return EINTR. I still wonder from which context the 'killable' property is used. btrfs_alloc_data_chunk_ondemand is indirectly inside zero range and fallocate, there it makes sense. With flush_space is less obvious, so this should be explained in the changelog what's expected. > + */ > +int btrfs_wait_on_delayed_iputs(struct btrfs_fs_info *fs_info) > +{ > + int ret = wait_event_killable(fs_info->delayed_iputs_wait, > + atomic_read(&fs_info->nr_delayed_iputs) == 0); > + if (ret) > + return -EINTR; > + return 0; > +} > + > /* > * This creates an orphan entry for the given inode in case something goes wrong > * in the middle of an unlink. > -- > 2.14.3