linux-kernel - Re: [PATCH] nfs: Don't try mounting device as nfs root unless type fully matches

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Message-ID: <1326111265.30169.5.camel@lappy>
Date:	Mon, 09 Jan 2012 14:14:25 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Jim Rees <rees@...ch.edu>
Cc:	Chuck Lever <chuck.lever@...cle.com>, linux@...ik.name,
	Trond.Myklebust@...app.com, penberg@...nel.org,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfs: Don't try mounting device as nfs root unless type
 fully matches

On Sat, 2012-01-07 at 13:12 -0500, Jim Rees wrote:
> Chuck Lever wrote:
> 
>   On Jan 7, 2012, at 4:12 AM, Sasha Levin wrote:
>   
>   > Currently, we'll try mounting any device who's major device number is
>   > UNNAMED_MAJOR as NFS root. This would happen for non-NFS devices as well (such
>   > as 9p devices) but it wouldn't cause any issues since mounting the device
>   > as NFS would fail quickly and the code proceeded to doing the proper mount:
>   > 
>   > 	[  101.522716] VFS: Unable to mount root fs via NFS, trying floppy.
>   > 	[  101.534499] VFS: Mounted root (9p filesystem) on device 0:18.
>   > 
>   > Commit 6829a048 ("NFS: Retry mounting NFSROOT") has introduced retries when
>   > mounting NFS root, which means that now we don't immediately fail and instead
>   > it takes an additional 90+ seconds until we stop retrying.
>   > 
>   > This meant that it would take an additional 90 seconds to boot when we're not
>   > using a device type which gets detected in order before NFS.
>   
>   The long timeouts are kind of irrelevant, in my view.  The real problem is
>   that NFS was tried at all in this case.  That behavior was not introduced
>   by 6829a058.
> 
> The comment does imply that 6829a048 introduced a bug, but that's not true.
> It uncovered a bug that was there before.
> 
> I would change the part about "now we don't immediately fail."  It didn't
> immediately fail before, but the timeout was short enough that you wouldn't
> notice it.

I tried to point out that 6829a048 changed the behavior which was
described in the first paragraph, I didn't try to imply that 6829a048 is
buggy on its own.

I'm fine with changing the changelog to whatever will make it clearer.

-- 

Sasha.

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