linux-kernel - Re: ext4: cache all of an extent tree's leaf block upon reading

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Message-ID: <20130905190837.GD23661@thunk.org>
Date:	Thu, 5 Sep 2013 15:08:37 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: ext4: cache all of an extent tree's leaf block upon reading

On Thu, Sep 05, 2013 at 11:14:57AM -0400, Dave Jones wrote:
>  > So the only reason to add a line explicitly setting es_pblk to zero
>  > would be to suppress a warning from some insufficiently smart static
>  > code analysis tool.  I didn't see a warning from gcc, but it's
>  > possible that this is something which is causing Coverity or some
>  > other code scanner heartburn.
> 
> Yep, that's what picked it up.  I'll add a 'not a bug' annotation to stop
> it getting flagged again.  This was the only ext* issue that Coverity
> picked up from yesterdays merge btw, which I guess is good news ;)

Indeed.

Hmm...  I could add a new inline function
"ext4_es_store_pblock_status()" which sets both parts of the es_pblk
word at once, and which doesn't depend looking at its original value
at all.  I doubt we would never measure a difference in performance,
but in theory it would be more efficient.  And if it eliminates a
potential static code analysis complaint, maybe the two justifications
is good enough to add the new function.

Thanks for checking the coverity results!!

						- Ted
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