linux-kernel - Re: [PATCH] cleanup block based fiemap

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Message-ID: <alpine.LFD.2.00.1004230825481.3739@i5.linux-foundation.org>
Date:	Fri, 23 Apr 2010 08:27:02 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Josef Bacik <josef@...hat.com>
cc:	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, randy.dunlap@...cle.com
Subject: Re: [PATCH] cleanup block based fiemap



On Fri, 23 Apr 2010, Josef Bacik wrote:
> 
> __generic_block_fiemap is called by generic_block_fiemap which takes the
> i_mutex.  The only reason we have __generic_block_fiemap is because gfs2 needs
> to do its own locking magic before we go calling get_block.  The idea is that
> the file size doesn't change while we're doing this.

Ok, maybe just a comment then..

> As for reading the size several times, I can read it once and store it in a
> local variable if you prefer, but theres no way to know if len is smaller than
> the size or not, which is why I'm constantly doing i_size_read().  If thats what
> you would prefer I can do that, just let me know.

.. or a comment _and_ a "read size once into a variable". Not a big deal, 
it just wasn't entirely clear to me and I hadn't checked the callchain.

> > Issue #2: "blk_to_logical(inode, 0)"? WTF? Since when has shifting zero 
> > ever resulted in anything interesting or relevant? There's at least two of 
> > those things.
> > 
> 
> Umm, yeah I'm sorry?  I have no idea why I did that.  I think its because I was
> getting the logical offset of the first block + size, which is just stupid
> because the logical offset is 0, so all I can say is I'm sorry that me a year
> ago was alot dumber than me now :).  Thanks,

Ok, fix that, and I think the patch will be a clear improvement.

		Linus
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