[linux-cifs-client] mkstemp fails on cifs linux-2.6.31-rc1 / samba-3.3.6

[Shirish Pargaonkar]

On Wed, Jul 1, 2009 at 7:13 AM, Jeff Layton<jlayton at redhat.com> wrote:
> On Wed, 2009-07-01 at 06:59 -0500, Shirish Pargaonkar wrote:
>> On Wed, Jul 1, 2009 at 6:21 AM, Jeff Layton<jlayton at redhat.com> wrote:
>> > On Wed, 2009-07-01 at 06:01 -0500, Shirish Pargaonkar wrote:
>> >>
>> >> I think the problem is, why EEXIST since file does not exist.  The
>> >> looping is I guess
>> >> because mktemp then attempts to create another file and receives EEXIST and it
>> >> goes on forever.
>> >> So the basic issues is why EEXIST since mktemp is attempting a file
>> >> which does not
>> >> exist on the server.
>> >
>> > The problem is that the lookup is returning a positive dentry since it
>> > just created the file. This makes the VFS turn around and return -EEXIST
>> > (see the second O_EXCL check in do_filp_open). So we do have to skip the
>> > create on lookup for O_EXCL or it won't work.
>> >
>> > I think what's needed is something like this patch. It seems to fix the
>> > testcase for me. That said, this is not adequately regression tested and
>> > should not be committed until it is.
>> >
>> > On that note, I'd like to reiterate my earlier sentiment that all of
>> > this create-on-lookup code was committed prematurely and should be
>> > backed out until it's more fully baked.
>> >
>> > Just my USD$.02...
>> >
>> > --
>> > Jeff Layton <jlayton at redhat.com>
>> >
>>
>> meant to send this to everybody but ended up sending only to Jeff,
>> so here it is again...
>>
>> I think that is why it is not possible to exclusive create within
>> lookup intent code.
>> So, IMHO, we should put the check back in the cifs_lookup.
>> That is what NFS does, and cifs should do the same
>
> Right, but do we really need to do the lookup in that case? It seems
> like the old check didn't optimize it away (but maybe I'm remembering
> incorrectly).
>
> --
> Jeff Layton <jlayton at redhat.com>
>
>

With the check, we are back to what was before lookup intent for
exclusive create.  I think for exclusive create, a lookup can result in
not create if the file exists, so for a command like mktemp, it
probably does not help, there will be a lookup and there will be a create.