Linux-BTRFS Archive on lore.kernel.org
 help / color / Atom feed
From: Josef Bacik <josef@toxicpanda.com>
To: Nikolay Borisov <nborisov@suse.com>
Cc: Josef Bacik <josef@toxicpanda.com>,
	linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue
Date: Tue, 27 Nov 2018 15:01:35 -0500
Message-ID: <20181127200134.kmnu3zubgl7n4d4j@macbook-pro-91.dhcp.thefacebook.com> (raw)
In-Reply-To: <34807ceb-525c-2552-b2c0-a850da135f74@suse.com>

On Tue, Nov 27, 2018 at 10:29:57AM +0200, Nikolay Borisov wrote:
> 
> 
> On 21.11.18 г. 21:09 ч., Josef Bacik wrote:
> > The throttle path doesn't take cleaner_delayed_iput_mutex, which means
> 
> Which one is the throttle path? btrfs_end_transaction_throttle is only
> called during snapshot drop and relocation? What scenario triggered your
> observation and prompted this fix?
> 

One of my enospc tests runs snapshot creation/deletion in the background.

> > 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 <josef@toxicpanda.com>
> > ---
> >  fs/btrfs/ctree.h       |  4 +++-
> >  fs/btrfs/disk-io.c     |  5 ++---
> >  fs/btrfs/extent-tree.c |  9 +++++----
> >  fs/btrfs/inode.c       | 21 +++++++++++++++++++++
> >  4 files changed, 31 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index 709de7471d86..a835fe7076eb 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -912,7 +912,8 @@ 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;
> > @@ -3237,6 +3238,7 @@ 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 c5918ff8241b..3f81dfaefa32 100644
> > --- a/fs/btrfs/disk-io.c
> > +++ b/fs/btrfs/disk-io.c
> > @@ -1692,9 +1692,7 @@ 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);
> > @@ -2651,7 +2649,6 @@ 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);
> > @@ -2673,6 +2670,7 @@ 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;
> > @@ -2750,6 +2748,7 @@ 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 3a90dc1d6b31..36f43876be22 100644
> > --- a/fs/btrfs/extent-tree.c
> > +++ b/fs/btrfs/extent-tree.c
> > @@ -4272,8 +4272,9 @@ int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes)
> >  				 * operations. Wait for it to finish so that
> >  				 * more space is released.
> >  				 */
> > -				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);
> > @@ -4838,9 +4839,9 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> >  	 * 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);
> > +	wait_event(fs_info->delayed_iputs_wait,
> > +		   atomic_read(&fs_info->nr_delayed_iputs) == 0);
> 
> Why open code btrfs_wait_on_delayed_iputs(fs_info)? Just make it use
> wait_event instead of the killable version and use the function
> uniformally across the code base.

I don't want the flusher thread to be killable, but now that I've said that out
loud I realize that's not possible, so I'll just use the helper.  Thanks,

Josef

  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-21 19:09 [PATCH 0/3] Delayed iput fixes Josef Bacik
2018-11-21 19:09 ` [PATCH 1/3] btrfs: run delayed iputs before committing Josef Bacik
2018-11-26 14:44   ` Nikolay Borisov
2018-11-21 19:09 ` [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput Josef Bacik
2018-11-27  8:26   ` Nikolay Borisov
2018-11-27 19:54     ` Josef Bacik
2018-11-27 19:59       ` Chris Mason
2018-11-27 20:08         ` Josef Bacik
2018-11-28 19:06           ` David Sterba
2018-11-28 19:32             ` Chris Mason
2018-11-28 20:08             ` Filipe Manana
2018-11-29  0:30               ` Qu Wenruo
2018-11-21 19:09 ` [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue Josef Bacik
2018-11-27  8:29   ` Nikolay Borisov
2018-11-27 20:01     ` Josef Bacik [this message]
2018-12-03 16:06 [PATCH 0/3][V2] Delayed iput fixes Josef Bacik
2018-12-03 16:06 ` [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue Josef Bacik
2018-12-04 11:46   ` Nikolay Borisov
2018-12-04 18:21     ` Josef Bacik
2019-01-11 15:21 [PATCH 0/3][V3] Delayed iput fixes Josef Bacik
2019-01-11 15:21 ` [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue Josef Bacik
2019-01-16 19:12   ` David Sterba
2019-02-05 18:23     ` David Sterba

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181127200134.kmnu3zubgl7n4d4j@macbook-pro-91.dhcp.thefacebook.com \
    --to=josef@toxicpanda.com \
    --cc=kernel-team@fb.com \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=nborisov@suse.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-BTRFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-btrfs/0 linux-btrfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-btrfs linux-btrfs/ https://lore.kernel.org/linux-btrfs \
		linux-btrfs@vger.kernel.org linux-btrfs@archiver.kernel.org
	public-inbox-index linux-btrfs


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-btrfs


AGPL code for this site: git clone https://public-inbox.org/ public-inbox