linux-kernel - Re: [RFC PATCH V2 2/2] ext4: Replace the __block_write_begin with ext4_block_write

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Message-ID: <20240809165548.nlhsovccmn3kmouw@quack3>
Date: Fri, 9 Aug 2024 18:55:48 +0200
From: Jan Kara <jack@...e.cz>
To: zhangshida <starzhangzsd@...il.com>
Cc: tytso@....edu, adilger.kernel@...ger.ca, jack@...e.com,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	zhangshida@...inos.cn, Jan Kara <jack@...e.cz>
Subject: Re: [RFC PATCH V2 2/2] ext4: Replace the __block_write_begin with
 ext4_block_write_begin

On Fri 09-08-24 14:46:06, zhangshida wrote:
> From: Shida Zhang <zhangshida@...inos.cn>
> 
> Using __block_write_begin() make it inconvenient to journal the
> user data dirty process. We can't tell the block layer maintainer,
> ‘Hey, we want to trace the dirty user data in ext4, can we add some
> special code for ext4 in __block_write_begin?’:P
> 
> So use ext4_block_write_begin() instead.
> 
> The two functions are basically doing the same thing except for the
> fscrypt related code. Narrow the scope of CONFIG_FS_ENCRYPTION
> so as to allow ext4_block_write_begin() to function like
> __block_write_begin when the config is disabled.
> 
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Shida Zhang <zhangshida@...inos.cn>

There are three more calls to __block_write_begin() in fs/ext4/inline.c.
Please convert them as well. We don't allow inline data and data
journalling combination but it is unexpected surprise that those places
still use __block_write_begin().

								Honza

> ---
>  fs/ext4/inode.c | 19 ++++---------------
>  1 file changed, 4 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index de46c0a6842a..31389633086a 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1046,7 +1046,6 @@ int do_journal_get_write_access(handle_t *handle, struct inode *inode,
>  	return ret;
>  }
>  
> -#ifdef CONFIG_FS_ENCRYPTION
>  static int ext4_block_write_begin(handle_t *handle, struct folio *folio,
>  				  loff_t pos, unsigned len,
>  				  get_block_t *get_block)
> @@ -1135,7 +1134,9 @@ static int ext4_block_write_begin(handle_t *handle, struct folio *folio,
>  							 from, to);
>  		else
>  			folio_zero_new_buffers(folio, from, to);
> -	} else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> +	}
> +#ifdef CONFIG_FS_ENCRYPTION
> +	else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
>  		for (i = 0; i < nr_wait; i++) {
>  			int err2;
>  
> @@ -1147,10 +1148,10 @@ static int ext4_block_write_begin(handle_t *handle, struct folio *folio,
>  			}
>  		}
>  	}
> +#endif
>  
>  	return err;
>  }
> -#endif
>  
>  /*
>   * To preserve ordering, it is essential that the hole instantiation and
> @@ -1232,20 +1233,12 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
>  	/* In case writeback began while the folio was unlocked */
>  	folio_wait_stable(folio);
>  
> -#ifdef CONFIG_FS_ENCRYPTION
>  	if (ext4_should_dioread_nolock(inode))
>  		ret = ext4_block_write_begin(handle, folio, pos, len,
>  					     ext4_get_block_unwritten);
>  	else
>  		ret = ext4_block_write_begin(handle, folio, pos, len,
>  					     ext4_get_block);
> -#else
> -	if (ext4_should_dioread_nolock(inode))
> -		ret = __block_write_begin(&folio->page, pos, len,
> -					  ext4_get_block_unwritten);
> -	else
> -		ret = __block_write_begin(&folio->page, pos, len, ext4_get_block);
> -#endif
>  	if (!ret && ext4_should_journal_data(inode)) {
>  		ret = ext4_walk_page_buffers(handle, inode,
>  					     folio_buffers(folio), from, to,
> @@ -2978,12 +2971,8 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
>  	if (IS_ERR(folio))
>  		return PTR_ERR(folio);
>  
> -#ifdef CONFIG_FS_ENCRYPTION
>  	ret = ext4_block_write_begin(NULL, folio, pos, len,
>  				     ext4_da_get_block_prep);
> -#else
> -	ret = __block_write_begin(&folio->page, pos, len, ext4_da_get_block_prep);
> -#endif
>  	if (ret < 0) {
>  		folio_unlock(folio);
>  		folio_put(folio);
> -- 
> 2.33.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR