linux-ext4 - Re: [PATCH 1/6 ]Ext4 credits caclulation cleanup and fix that for nonextent writepage

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Date:	Wed, 13 Aug 2008 14:01:32 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Mingming Cao <cmm@...ibm.com>
Cc:	tytso <tytso@....edu>, linux-ext4@...r.kernel.org,
	Andreas Dilger <adilger@....com>
Subject: Re: [PATCH 1/6 ]Ext4 credits caclulation cleanup and fix that for
	nonextent writepage

On Tue, Aug 12, 2008 at 09:25:54AM -0700, Mingming Cao wrote:

....


> - * and dindirect block, and the "5" above becomes "3".
> + * Also account for superblock, inode, quota and xattr blocks
> + */
> +int ext4_meta_trans_blocks(struct inode* inode, int nrblocks, int idxblocks)
> +{
> +	int groups, gdpblocks;
> +	int ret = 0;
> +
> +	groups = nrblocks + idxblocks;
> +	gdpblocks = groups;
> +	if (groups > EXT4_SB(inode->i_sb)->s_groups_count)
> +		groups = EXT4_SB(inode->i_sb)->s_groups_count;
> +	if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
> +		gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;
> +
> +	/* bitmaps and block group descriptor blocks */
> +	ret += groups + gdpblocks;


	ret = groups + gdpblocks;

> +
> +	ret += idxblocks;
> +
> +	/* journalled mode, include buffer to modify data blocks */
> +	if (ext4_should_journal_data(inode))
> +		ret += nrblocks;
> +
> +	/* Blocks for super block, inode, quota and xattr blocks */
> +	ret += EXT4_META_TRANS_BLOCKS(inode->i_sb);
> +
> +	return ret;
> +}
> +
> +static int ext4_indirect_trans_blocks(struct inode *inode, int nrblocks,
> +				      int chunk)
> +{

.....
.....

> 
> +/*
> + * Define the number of metadata blocks we need to account to modify data.
> + *
> + * This include super block, inode block, quota blocks and xattr blocks
> + */
> +#define EXT4_META_TRANS_BLOCKS(sb)	(EXT4_XATTR_TRANS_BLOCKS + \
> +					2*EXT4_QUOTA_TRANS_BLOCKS(sb))
> +

Do EXT4_XATTR_TRANS_BLOCKS blocks really account for super block
and inode block ? Looking at EXT4_DATA_TRANS_BLOCKS which also use
EXT4_XATTR_TRANS_BLOCKS I think it doesn't. But the comment above
EXT4_XATTR_TRANS_BLOCKS is confusing. I guess we would need a +2 here.



-aneesh
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