[16/29] ext4: Improve writepage credit estimate for files with indirect blocks

ext4_ind_trans_blocks() wrongly used 'chunk' argument to decide whether
blocks mapped are logically continguous. That is wrong since the argument
informs whether the blocks are physically continguous. As the blocks
mapped are always logically continguous and that's all
ext4_ind_trans_blocks() cares about, just remove the 'chunk' argument.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/ext4.h     |    2 +-
 fs/ext4/indirect.c |   27 +++++++++------------------
 fs/ext4/inode.c    |    2 +-
 3 files changed, 11 insertions(+), 20 deletions(-)

On Mon, Apr 08, 2013 at 11:32:21PM +0200, Jan Kara wrote:
> ext4_ind_trans_blocks() wrongly used 'chunk' argument to decide whether
> blocks mapped are logically continguous. That is wrong since the argument
> informs whether the blocks are physically continguous. As the blocks
> mapped are always logically continguous and that's all
> ext4_ind_trans_blocks() cares about, just remove the 'chunk' argument.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Regards,
                                                - Zheng

> ---
>  fs/ext4/ext4.h     |    2 +-
>  fs/ext4/indirect.c |   27 +++++++++------------------
>  fs/ext4/inode.c    |    2 +-
>  3 files changed, 11 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 3575fdb..d3a54f2 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2093,7 +2093,7 @@ extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
>  				const struct iovec *iov, loff_t offset,
>  				unsigned long nr_segs);
>  extern int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock);
> -extern int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk);
> +extern int ext4_ind_trans_blocks(struct inode *inode, int nrblocks);
>  extern void ext4_ind_truncate(struct inode *inode);
>  extern int ext4_ind_punch_hole(struct file *file, loff_t offset, loff_t length);
>  
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index b505a14..197b202 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -913,27 +913,18 @@ int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
>  	return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
>  }
>  
> -int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk)
> +/*
> + * Calculate number of indirect blocks touched by mapping @nrblocks logically
> + * continguous blocks
> + */
> +int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
>  {
> -	int indirects;
> -
> -	/* if nrblocks are contiguous */
> -	if (chunk) {
> -		/*
> -		 * With N contiguous data blocks, we need at most
> -		 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
> -		 * 2 dindirect blocks, and 1 tindirect block
> -		 */
> -		return DIV_ROUND_UP(nrblocks,
> -				    EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
> -	}
>  	/*
> -	 * if nrblocks are not contiguous, worse case, each block touch
> -	 * a indirect block, and each indirect block touch a double indirect
> -	 * block, plus a triple indirect block
> +	 * With N contiguous data blocks, we need at most
> +	 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
> +	 * 2 dindirect blocks, and 1 tindirect block
>  	 */
> -	indirects = nrblocks * 2 + 1;
> -	return indirects;
> +	return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
>  }
>  
>  /*
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index f4dc4a1..aa26f4c 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4399,7 +4399,7 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
>  static int ext4_index_trans_blocks(struct inode *inode, int nrblocks, int chunk)
>  {
>  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
> -		return ext4_ind_trans_blocks(inode, nrblocks, chunk);
> +		return ext4_ind_trans_blocks(inode, nrblocks);
>  	return ext4_ext_index_trans_blocks(inode, nrblocks, chunk);
>  }
>  
> -- 
> 1.7.1
> 
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