linux-kernel - Re: [GIT PULL] block drivers for 2.6.39-rc

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Date:	Mon, 28 Mar 2011 16:06:57 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jens Axboe <jaxboe@...ionio.com>,
	"Stephen M. Cameron" <scameron@...rdog.cce.hp.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] block drivers for 2.6.39-rc

On Sat, Mar 26, 2011 at 11:56 AM, Jens Axboe <jaxboe@...ionio.com> wrote:
> Hi Linus,
>
> This is the pull request for the block driver updates for 2.6.39. Two
> things here:
>
> - Big drbd update, as per usual...
> - cciss update.

Btw, that cciss thing causes a very annoying compiler warning:

  drivers/block/cciss.c: In function ‘dev_show_unique_id’:
  drivers/block/cciss.c:617:7: warning: ‘sn[0]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[1]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[2]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[3]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[4]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[5]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[6]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[7]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[8]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[9]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[10]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[11]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[12]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[13]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[14]’ may be used
uninitialized in this function
  drivers/block/cciss.c:617:7: warning: ‘sn[15]’ may be used
uninitialized in this function

which is because the compiler doesn't really notice that those things
are only used if the error return isn't being set.

So it's a compiler mis-feature, but the thing is, the warning could
easily be avoided by just writing the code more prettily.

Just do the memcpy() unconditionally: we know that 'drv' is a valid
pointer (we just loaded 'h' off it), and we're talking about a nice
constant 16-byte copy.

IOW, a patch something like the attached.

Untested, but it looks really obvious. Hmm?

                            Linus

View attachment "patch.diff" of type "text/x-patch" (1175 bytes)