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Date: Thu, 25 Mar 2010 14:06:05 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Benny Halevy <bhalevy@panasas.com>
Cc: Boaz Harrosh <bharrosh@panasas.com>,
       linux-fsdevel <linux-fsdevel@vger.kernel.org>,
       "J. Bruce Fields" <bfields@citi.umich.edu>,
       pNFS Mailing List <pnfs@linux-nfs.org>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Doug Nazar <nazard.lkml@gmail.com>,
       Trond Myklebust <Trond.Myklebust@netapp.com>
Subject: Re: [pnfs] [GIT BISECT] first bad commit: 1f36f774 Switch !O_CREAT
 case to use of do_last()
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On Thu, Mar 25, 2010 at 03:52:25PM +0200, Benny Halevy wrote:
> On Mar. 25, 2010, 15:37 +0200, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> > On Thu, Mar 25, 2010 at 03:30:22PM +0200, Boaz Harrosh wrote:
> >>> Let's try this: before do_lookup() call there add
> >>> 	if (*want_dir)
> >>> 		nd->flags |= LOOKUP_DIRECTORY;
> >> Yes this fixes it!!
> >> 2.6.34-rc2 plus above, now works, horay. (diff attached)
> >>
> >>> and see how does it behave.
> >>>
> >>> However, even if it does help, it doesn't explain everything.  Normal
> >>> open() on a directory without O_DIRECTORY if flags shouldn't fail with
> >>> -EISDIR.  How did that manage to avoid it all along?
> > 
> > Does open() of directory _without_ O_DIRECTORY work in e.g. vanilla 2.6.33?
> > It certainly does for local filesystems and it does for NFSv3; does it work
> > for NFSv4?
> 
> No, it doesn't.
> 
> # mount localhost:/usr0/nfs4export /mnt/localhost; strace cat /mnt/localhost/server 2>&1 | grep 'open.*server'; umount /mnt/localhost
> open("/mnt/localhost/server", O_RDONLY) = 3
> 
> # mount -t nfs4 localhost:/ /mnt/localhost; strace cat /mnt/localhost/server 2>&1 | grep 'open.*server'; umount /mnt/localhost
> open("/mnt/localhost/server", O_RDONLY) = -1 EISDIR (Is a directory)

Gets better - if you do ls -l /mnt/localhost/server and then repeat that
open(), it'll succeed.