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Date:	Wed, 26 Sep 2012 16:05:38 +0200
From:	Jan Kara <jack@...e.cz>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	linux-ext4@...r.kernel.org, tytso@....edu, jack@...e.cz,
	lczerner@...hat.com
Subject: Re: [PATCH 08/10] ext4: endless truncate due to nonlocked dio
 readers V2

On Mon 24-09-12 15:44:18, Dmitry Monakhov wrote:
> If we have enough aggressive DIO readers, truncate and other dio
> waiters will wait forever inside inode_dio_wait(). It is reasonable
> to disable nonlock DIO read optimization during truncate.
  Umm, actually this is a problem with any inode_dio_wait() call in ext4,
isn't it? So I'd just create ext4_inode_dio_wait() doing
	ext4_inode_block_unlocked_dio(inode);
	inode_dio_wait(inode);
	ext4_inode_resume_unlocked_dio(inode);

and use it instead of inode_dio_wait().

								Honza
 
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
>  fs/ext4/inode.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 32e9701..d3f86e7 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4330,9 +4330,13 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
>  	if (attr->ia_valid & ATTR_SIZE) {
>  		if (attr->ia_size != inode->i_size) {
>  			truncate_setsize(inode, attr->ia_size);
> -			/* Inode size will be reduced, wait for dio in flight */
> -			if (orphan)
> +			/* Inode size will be reduced, wait for dio in flight.
> +			 * Temproraly disable unlocked DIO to prevent livelock */
                           ^^ Temporarily

> +			if (orphan) {
> +				ext4_inode_block_unlocked_dio(inode);
>  				inode_dio_wait(inode);
> +				ext4_inode_resume_unlocked_dio(inode);
> +			}
>  		}
>  		ext4_truncate(inode);
>  	}
> -- 
> 1.7.7.6
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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