linux-ext4 - Re: [PATCH v2] ext4: ignore EXT4_INODE_JOURNAL

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Date:	Fri, 20 Jan 2012 13:09:37 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Ted Ts'o" <tytso@....edu>
cc:	Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
	Eric Sandeen <sandeen@...hat.com>
Subject: Re: [PATCH v2] ext4: ignore EXT4_INODE_JOURNAL_DATA flag with
 delalloc

On Thu, 19 Jan 2012, Ted Ts'o wrote:

> On Thu, Jan 12, 2012 at 12:03:44PM +0100, Lukas Czerner wrote:
> > +	/* We do not support data journalling with delayed allocation */
> > +	if (!S_ISREG(inode->i_mode) ||
> > +	   (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) ||
> > +	   (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA) &&
> > +	   !test_opt(inode->i_sb, DELALLOC)))
> > +		return EXT4_INODE_JOURNAL_DATA_MODE;	/* journal data */
> 
> It's probably clearer to make avoid the complex boolean expression:
> 
> 	if (!S_ISREG(inode->i_mode))
> 		return EXT4_INODE_JOURNAL_DATA_MODE;
> 	if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA))
> 		return EXT4_INODE_JOURNAL_DATA_MODE;
> 	if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA) &&
> 	    !test_opt(inode->i_sb, DELALLOC)))
> 		return EXT4_INODE_JOURNAL_DATA_MODE;
> 
> You could combine the first two condiionals:
> 
> 	if (!S_ISREG(inode->i_mode) ||
> 	    test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
> 		return EXT4_INODE_JOURNAL_DATA_MODE;
> 	if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA) &&
> 	    !test_opt(inode->i_sb, DELALLOC)))
> 		return EXT4_INODE_JOURNAL_DATA_MODE;
> 
> ... but combining || and && where someone has to squint and count
> parenthesis can be error-prone.  I can look at either of the above two
> and understand quickly what's going on.  With what you had (especially
> since the identation of !test_opt(...) wasn't quite right, I had to
> squint and think for a bit before I convince dmyself it was correct.
> 
> Otherwise, looks good!
> 
> 					- Ted

Thanks Ted, you're right it is much clearer this way. I'll resend the
patch.

-Lukas
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