From: Mingming Cao <cmm@us.ibm.com>
Subject: Re: [PATCH 1/6 ]Ext4 credits caclulation cleanup and fix that for
	nonextent writepage
Date: Wed, 13 Aug 2008 18:02:06 -0700
Message-ID: <1218675726.6387.23.camel@mingming-laptop>
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Cc: tytso <tytso@mit.edu>, linux-ext4@vger.kernel.org,
	Andreas Dilger <adilger@sun.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
In-Reply-To: <20080813101943.GF6439@skywalker>
Sender: linux-ext4-owner@vger.kernel.org


=E5=9C=A8 2008-08-13=E4=B8=89=E7=9A=84 15:49 +0530=EF=BC=8CAneesh Kumar=
 K.V=E5=86=99=E9=81=93=EF=BC=9A
> 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 =3D 0;
> > +
> > +	groups =3D nrblocks + idxblocks;
> > +	gdpblocks =3D groups;
> > +	if (groups > EXT4_SB(inode->i_sb)->s_groups_count)
> > +		groups =3D EXT4_SB(inode->i_sb)->s_groups_count;
> > +	if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
> > +		gdpblocks =3D EXT4_SB(inode->i_sb)->s_gdb_count;
>=20
>=20
> 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,=20
> if(chunk)
> 	groups =3D 1 + idxblocks;
>=20
>=20

Agree. will update the patch to do that
Mingming
>=20
> > +
> > +	/* bitmaps and block group descriptor blocks */
> > +	ret +=3D groups + gdpblocks;
> > +
> > +	ret +=3D idxblocks;
> > +
> > +	/* journalled mode, include buffer to modify data blocks */
> > +	if (ext4_should_journal_data(inode))
> > +		ret +=3D nrblocks;
> > +
> > +	/* Blocks for super block, inode, quota and xattr blocks */
> > +	ret +=3D EXT4_META_TRANS_BLOCKS(inode->i_sb);
> > +
> > +	return ret;
> > +}
> > +
> ....
> ...
>=20
> > +static int ext4_writeblocks_trans_credits_old(struct inode *inode,=
 int nrblocks,
> > +					      int chunk)
> >  {
> > -	int bpp =3D ext4_journal_blocks_per_page(inode);
> > -	int indirects =3D (EXT4_NDIR_BLOCKS % bpp) ? 5 : 3;
> > +	int indirects;
> >  	int ret;
> >=20
> > -	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
> > -		return ext4_ext_writepage_trans_blocks(inode, bpp);
> > -
> > -	if (ext4_should_journal_data(inode))
> > -		ret =3D 3 * (bpp + indirects) + 2;
> > -	else
> > -		ret =3D 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" fl=
ag
> > +	 */
> > +	indirects =3D ext4_indirect_trans_blocks(inode, nrblocks, chunk);
> >=20
> > -#ifdef CONFIG_QUOTA
> > -	/* We know that structure was already allocated during DQUOT_INIT=
 so
> > -	 * we will be updating only the data blocks + inodes */
> > -	ret +=3D 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 =3D ext4_meta_trans_blocks(inode, nrblocks, indirects);
> >=20
> >  	return ret;
> >  }
>=20
> -aneesh

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