Re: [PATCH] nfs: fix v4.2 SEEK on files over 2 gigs

["J. Bruce Fields" <bfields@fieldses.org>]

On Thu, Sep 17, 2015 at 09:04:00AM -0400, Anna Schumaker wrote:
> Hey Bruce,
> 
> I actually worked on a version of this patch on my own yesterday, too.  Looks like you beat me to submitting it!  :)

Oh, OK, well feel free to credit it however you'd like.

> On 09/16/2015 05:21 PM, J. Bruce Fields wrote:
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > We're incorrectly assigning a loff_t return to an int.  If SEEK_HOLE or
> > SEEK_DATA returns an offset over 2^31 then the application will see a
> > weird lseek() result (usually -EIO).
> 
> I saw roughly the same thing with xfstests generic/285.

I maybe should have included my reproducer in the changelog, which was:

	git clone git://git.infradead.org/users/dedekind/bmap-tools.git
	cd bmap-tools

	mount overs=4.2 localhost:/exports /mnt/
	dd if=/dev/zero of=/mnt/test1.image seek=2097152 bs=1K count=1

	./bmaptool  create  /mnt/test1.image

In the good case it outputs some xml, in the bad case it aborts with an
IO error.

--b.

> > Cc: stable@vger.kernel.org
> > Fixes: bdcc2cd14e4e "NFSv4.2: handle NFS-specific llseek errors"
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> Reviewed-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> 
> > ---
> >  fs/nfs/nfs42proc.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> > index d731bbf974aa..0f020e4d8421 100644
> > --- a/fs/nfs/nfs42proc.c
> > +++ b/fs/nfs/nfs42proc.c
> > @@ -175,10 +175,12 @@ loff_t nfs42_proc_llseek(struct file *filep, loff_t offset, int whence)
> >  {
> >  	struct nfs_server *server = NFS_SERVER(file_inode(filep));
> >  	struct nfs4_exception exception = { };
> > -	int err;
> > +	loff_t err;
> >  
> >  	do {
> >  		err = _nfs42_proc_llseek(filep, offset, whence);
> > +		if (err >= 0)
> > +			break;
> >  		if (err == -ENOTSUPP)
> >  			return -EOPNOTSUPP;
> >  		err = nfs4_handle_exception(server, err, &exception);
> >