linux-ext4 - Re: [PATCH 2/2] ext4: fix cpu_vs

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Message-ID: <87txnnpq0j.fsf@openvz.org>
Date:	Wed, 03 Apr 2013 19:55:56 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, wenqing.lz@...bao.com
Subject: Re: [PATCH 2/2] ext4: fix cpu_vs_disk conversions

On Wed, 3 Apr 2013 11:37:42 -0400, Theodore Ts'o <tytso@....edu> wrote:
> On Wed, Apr 03, 2013 at 02:58:31PM +0400, Dmitry Monakhov wrote:
> > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> > index 3a120b2..34da740 100644
> > --- a/fs/ext4/xattr.c
> > +++ b/fs/ext4/xattr.c
> > @@ -123,16 +123,15 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
> >  {
> >  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> >  	__u32 csum, old;
> > -
> > -	old = hdr->h_checksum;
> > +	__le64 dsk_block_nr = cpu_to_le64(block_nr);
> > +	old = le32_to_cpu(hdr->h_checksum);
> 
> We're just saving and restoring hdr->h_checksum.  So instead of
> byte-swapping the checksum in old, and then swapping it back, why not
> just do this instead:
> 
>      __le32 old;
> 
>      old = hdr->h_checksum;
>      ...
>      hdr->h_checksum = old;
yes. obviously that is correct.
> 
> 					- Ted
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