linux-ext4 - Re: [PATCH 1/3] ext4: Retry allocation when inline->extent conversion failed

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Date:	Thu, 12 Dec 2013 14:44:22 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Ted Tso <tytso@....edu>, Akira Fujita <a-fujita@...jp.nec.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/3] ext4: Retry allocation when inline->extent
 conversion failed

Hi Jan,

On Tue, Dec 10, 2013 at 11:13:58AM +0100, Jan Kara wrote:
> Similarly as other ->write_begin functions in ext4, also
> ext4_da_write_inline_data_begin() should retry allocation if the
> conversion failed because of ENOSPC. This avoids returning ENOSPC
> prematurely because of uncommitted block deletions.

I don't see why we need to try again here.  If there is no enough space
in inline data, ext4_da_convert_inline_data_to_extent() just read the
inline data into a page and clear EXT4_STATE_MAY_INLINE_DATA flag.  If
we try again, we will encounter an ENOSPC error again.  So why do we
need to retry allocation?

Thanks,
                                                - Zheng

> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/inline.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index bae987549dc3..ed6e71fe5e9d 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -849,11 +849,13 @@ int ext4_da_write_inline_data_begin(struct address_space *mapping,
>  	handle_t *handle;
>  	struct page *page;
>  	struct ext4_iloc iloc;
> +	int retries;
>  
>  	ret = ext4_get_inode_loc(inode, &iloc);
>  	if (ret)
>  		return ret;
>  
> +retry_journal:
>  	handle = ext4_journal_start(inode, EXT4_HT_INODE, 1);
>  	if (IS_ERR(handle)) {
>  		ret = PTR_ERR(handle);
> @@ -875,6 +877,11 @@ int ext4_da_write_inline_data_begin(struct address_space *mapping,
>  							    inode,
>  							    flags,
>  							    fsdata);
> +		ext4_journal_stop(handle);
> +		handle = NULL;
> +		if (ret == -ENOSPC &&
> +		    ext4_should_retry_alloc(inode->i_sb, &retries))
> +			goto retry_journal;
>  		goto out;
>  	}
>  
> -- 
> 1.8.1.4
> 
> --
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