linux-kernel - Re: [PATCH] fs: fix differed error reporting

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Message-ID: <20130415145342.GJ2299@quack.suse.cz>
Date:	Mon, 15 Apr 2013 16:53:42 +0200
From:	Jan Kara <jack@...e.cz>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	viro@...iv.linux.org.uk, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] fs: fix differed error reporting

On Thu 11-04-13 16:47:59, Dmitry Monakhov wrote:
> There are two convenient ways to report errors to userspace
> 1) retun error to original syscall for example write(2)
> 2) mark mapping with error flag and return it on later fsync(2)
> 
> Second one is broken if (mapping->nrpages == 0)
> This is real-life situation because after error pages are likey
> to be truncated or invalidated.
> 
> We have to return an error regardless to number of pages in the mapping.
> 
> #Original testcase: git@...hub.com:dmonakhov/xfstests.git
> MOUNT_OPTIONS="-b1024"
> ./check shared/305
  Makes sence to me. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>

  BTW, this more belongs to the mm area so Andrew Morton might be the right
person to merge this. Added to CC.

								Honza
> 
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
>  mm/filemap.c |   29 +++++++++++++++++++++--------
>  1 files changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index e1979fd..ca47f0b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -184,6 +184,17 @@ static int sleep_on_page_killable(void *word)
>  	return fatal_signal_pending(current) ? -EINTR : 0;
>  }
>  
> +static int filemap_check_errors(struct address_space *mapping)
> +{
> +	int ret = 0;
> +	/* Check for outstanding write errors */
> +	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
> +		ret = -ENOSPC;
> +	if (test_and_clear_bit(AS_EIO, &mapping->flags))
> +		ret = -EIO;
> +	return ret;
> +}
> +
>  /**
>   * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
>   * @mapping:	address space structure to write
> @@ -265,10 +276,10 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
>  	pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
>  	struct pagevec pvec;
>  	int nr_pages;
> -	int ret = 0;
> +	int ret2, ret = 0;
>  
>  	if (end_byte < start_byte)
> -		return 0;
> +		goto out;
>  
>  	pagevec_init(&pvec, 0);
>  	while ((index <= end) &&
> @@ -291,12 +302,10 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
>  		pagevec_release(&pvec);
>  		cond_resched();
>  	}
> -
> -	/* Check for outstanding write errors */
> -	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
> -		ret = -ENOSPC;
> -	if (test_and_clear_bit(AS_EIO, &mapping->flags))
> -		ret = -EIO;
> +out:
> +	ret2 = filemap_check_errors(mapping);
> +	if (!ret)
> +		ret = ret2;
>  
>  	return ret;
>  }
> @@ -337,6 +346,8 @@ int filemap_write_and_wait(struct address_space *mapping)
>  			if (!err)
>  				err = err2;
>  		}
> +	} else {
> +		err = filemap_check_errors(mapping);
>  	}
>  	return err;
>  }
> @@ -368,6 +379,8 @@ int filemap_write_and_wait_range(struct address_space *mapping,
>  			if (!err)
>  				err = err2;
>  		}
> +	} else {
> +		err = filemap_check_errors(mapping);
>  	}
>  	return err;
>  }
> -- 
> 1.7.1
> 
> --
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-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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