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

[Mingming Cao <cmm@us.ibm.com>]

在 2008-08-13三的 15:49 +0530，Aneesh Kumar K.V写道：
> On Tue, Aug 12, 2008 at 09:25:54AM -0700, Mingming Cao wrote:
> > +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;
> 
> 
> I guess we should pass chunk to ext4_meta_trans_blocks also.
> if (chunk) we should update only one group descriptor and one
> bitmap block ie, 
> if(chunk)
> 	groups = 1 + idxblocks;
> 
> 

Agree. will update the patch to do that
Mingming
> 
> > +
> > +	/* bitmaps and block group descriptor blocks */
> > +	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_writeblocks_trans_credits_old(struct inode *inode, int nrblocks,
> > +					      int chunk)
> >  {
> > -	int bpp = ext4_journal_blocks_per_page(inode);
> > -	int indirects = (EXT4_NDIR_BLOCKS % bpp) ? 5 : 3;
> > +	int indirects;
> >  	int ret;
> > 
> > -	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
> > -		return ext4_ext_writepage_trans_blocks(inode, bpp);
> > -
> > -	if (ext4_should_journal_data(inode))
> > -		ret = 3 * (bpp + indirects) + 2;
> > -	else
> > -		ret = 2 * (bpp + indirects) + 2;
> > +	/*
> > +	 * How many index blocks need to touch to modify nrblocks?
> > +	 * The "Chunk" flag indicating whether the nrblocks is
> > +	 * physically contigous on disk
> > +	 *
> > + 	 * For Direct IO and fallocate, they calls get_block to allocate
> > + 	 * one single extent at a time, so they could set the "Chunk" flag
> > +	 */
> > +	indirects = ext4_indirect_trans_blocks(inode, nrblocks, chunk);
> > 
> > -#ifdef CONFIG_QUOTA
> > -	/* We know that structure was already allocated during DQUOT_INIT so
> > -	 * we will be updating only the data blocks + inodes */
> > -	ret += 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
> > -#endif
> > +	/* Account for block group bitmaps and block groups
> > +	 * descriptors.Worse case, the nrblocks+indirects blocks spread
> > +	 * over different block groups
> > +	 */
> > +	ret = ext4_meta_trans_blocks(inode, nrblocks, indirects);
> > 
> >  	return ret;
> >  }
> 
> -aneesh

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