linux-kernel - Re: [PATCH] nfs: add missing selections of CONFIG

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Message-ID: <20250408204514.GA3142638@google.com>
Date: Tue, 8 Apr 2025 20:45:14 +0000
From: Eric Biggers <ebiggers@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>
Cc: linux-nfs@...r.kernel.org, Trond Myklebust <trondmy@...nel.org>,
	Anna Schumaker <anna@...nel.org>, Jeff Layton <jlayton@...nel.org>,
	Neil Brown <neilb@...e.de>, Olga Kornievskaia <okorniev@...hat.com>,
	Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
	Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfs: add missing selections of CONFIG_CRC32

On Wed, Apr 02, 2025 at 09:29:41AM -0700, Eric Biggers wrote:
> On Wed, Apr 02, 2025 at 09:51:05AM -0400, Chuck Lever wrote:
> > On 4/1/25 6:02 PM, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@...gle.com>
> > > 
> > > nfs.ko, nfsd.ko, and lockd.ko all use crc32_le(), which is available
> > > only when CONFIG_CRC32 is enabled.  But the only NFS kconfig option that
> > > selected CONFIG_CRC32 was CONFIG_NFS_DEBUG, which is client-specific and
> > > did not actually guard the use of crc32_le() even on the client.
> > > 
> > > The code worked around this bug by only actually calling crc32_le() when
> > > CONFIG_CRC32 is built-in, instead hard-coding '0' in other cases.  This
> > > avoided randconfig build errors, and in real kernels the fallback code
> > > was unlikely to be reached since CONFIG_CRC32 is 'default y'.  But, this
> > > really needs to just be done properly, especially now that I'm planning
> > > to update CONFIG_CRC32 to not be 'default y'.
> > 
> > It's interesting that no-one has noticed this before. dprintk is not the
> > only consumer of the FH hash function: NFS/NFSD trace points also use
> > it.
> > 
> > Eric, assuming you would like to carry this patch forward instead of us
> > taking it through one of the NFS client or server trees:
> > 
> > Acked-by: Chuck Lever <chuck.lever@...cle.com>
> > 
> > for the hunks related to nfsd and lockd.
> 
> Please go ahead and take it through one of the NFS trees.  Thanks!
> 

I ended up sending in the removal of 'default y' from CONFIG_CRC32 for 6.15.  So
I recommend that you send this NFS patch in for 6.15 as well, as it's now
slightly more likely that people can end up with CONFIG_CRC32 disabled (though
many other parts of the kernel select it anyway, so it still tends to be
enabled).

- Eric