Re: [PATCH 8/8] inode: don't softlockup when evicting inodes

From: Jan Kara <jack@suse.cz>
To: Josef Bacik <jbacik@fb.com>
Cc: linux-fsdevel@vger.kernel.org, kernel-team@fb.com,
	viro@ZenIV.linux.org.uk, hch@infradead.org, jack@suse.cz,
	david@fromorbit.com
Subject: Re: [PATCH 8/8] inode: don't softlockup when evicting inodes
Date: Mon, 15 Jun 2015 16:16:28 +0200	[thread overview]
Message-ID: <20150615141628.GI4368@quack.suse.cz> (raw)
In-Reply-To: <1434051673-13838-9-git-send-email-jbacik@fb.com>

On Thu 11-06-15 15:41:13, Josef Bacik wrote:
> On a box with a lot of ram (148gb) I can make the box softlockup after running
> an fs_mark job that creates hundreds of millions of empty files.  This is
> because we never generate enough memory pressure to keep the number of inodes on
> our unused list low, so when we go to unmount we have to evict ~100 million
> inodes.  This makes one processor a very unhappy person, so add a cond_resched()
> in dispose_list() and if we need a resched when processing the s_inodes list do
> that and run dispose_list() on what we've currently culled.  Thanks,
> 
> Signed-off-by: Josef Bacik <jbacik@fb.com>
  Looks good. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

								Honza
> ---
>  fs/inode.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index d1e6598..53a1224 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -574,6 +574,7 @@ static void dispose_list(struct list_head *head)
>  		list_del_init(&inode->i_lru);
>  
>  		evict(inode);
> +		cond_resched();
>  	}
>  }
>  
> @@ -591,6 +592,7 @@ void evict_inodes(struct super_block *sb)
>  	struct inode *inode, *next;
>  	LIST_HEAD(dispose);
>  
> +again:
>  	spin_lock(&sb->s_inode_list_lock);
>  	list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
>  		if (atomic_read(&inode->i_count))
> @@ -606,6 +608,18 @@ void evict_inodes(struct super_block *sb)
>  		inode_lru_list_del(inode);
>  		spin_unlock(&inode->i_lock);
>  		list_add(&inode->i_lru, &dispose);
> +
> +		/*
> +		 * We can have a ton of inodes to evict at unmount time given
> +		 * enough memory, check to see if we need to go to sleep for a
> +		 * bit so we don't livelock.
> +		 */
> +		if (need_resched()) {
> +			spin_unlock(&sb->s_inode_list_lock);
> +			cond_resched();
> +			dispose_list(&dispose);
> +			goto again;
> +		}
>  	}
>  	spin_unlock(&sb->s_inode_list_lock);
>  
> -- 
> 2.1.0
> 
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR