Re: Weird mount issue (Ubuntu 18.04, Ceph 14.2.5 & 14.2.6)

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On Fri, 2020-01-17 at 17:10 +0100, Ilya Dryomov wrote:
> On Fri, Jan 17, 2020 at 2:21 AM Aaron <aarongmldt@xxxxxxxxx> wrote:
> > No worries, can definitely do that.
> > 
> > Cheers
> > Aaron
> > 
> > On Thu, Jan 16, 2020 at 8:08 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > > On Thu, 2020-01-16 at 18:42 -0500, Jeff Layton wrote:
> > > > On Wed, 2020-01-15 at 08:05 -0500, Aaron wrote:
> > > > > Seeing a weird mount issue.  Some info:
> > > > > 
> > > > > No LSB modules are available.
> > > > > Distributor ID: Ubuntu
> > > > > Description: Ubuntu 18.04.3 LTS
> > > > > Release: 18.04
> > > > > Codename: bionic
> > > > > 
> > > > > Ubuntu 18.04.3 with kerne 4.15.0-74-generic
> > > > > Ceph 14.2.5 & 14.2.6
> > > > > 
> > > > > With ceph-common, ceph-base, etc installed:
> > > > > 
> > > > > ceph/stable,now 14.2.6-1bionic amd64 [installed]
> > > > > ceph-base/stable,now 14.2.6-1bionic amd64 [installed]
> > > > > ceph-common/stable,now 14.2.6-1bionic amd64 [installed,automatic]
> > > > > ceph-mds/stable,now 14.2.6-1bionic amd64 [installed]
> > > > > ceph-mgr/stable,now 14.2.6-1bionic amd64 [installed,automatic]
> > > > > ceph-mgr-dashboard/stable,stable,now 14.2.6-1bionic all [installed]
> > > > > ceph-mon/stable,now 14.2.6-1bionic amd64 [installed]
> > > > > ceph-osd/stable,now 14.2.6-1bionic amd64 [installed]
> > > > > libcephfs2/stable,now 14.2.6-1bionic amd64 [installed,automatic]
> > > > > python-ceph-argparse/stable,stable,now 14.2.6-1bionic all [installed,automatic]
> > > > > python-cephfs/stable,now 14.2.6-1bionic amd64 [installed,automatic]
> > > > > 
> > > > > I create a user via get-or-create cmd, and I have a users/secret now.
> > > > > When I try to mount on these Ubuntu nodes,
> > > > > 
> > > > > The mount cmd I run for testing is:
> > > > > sudo mount -t ceph -o
> > > > > name=user-20c5338c-34db-11ea-b27a-de7033e905f6,secret=AQC6dhpeyczkDxAAhRcr7oERUY4BcD2NCUkuNg==
> > > > > 10.10.10.10:6789:/work/20c5332d-34db-11ea-b27a-de7033e905f6 /tmp/test
> > > > > 
> > > > > I get the error:
> > > > > couldn't finalize options: -34
> > > > > 
> > > > > From some tracking down, it's part of the get_secret_option() in
> > > > > common/secrets.c and the Linux System Error:
> > > > > 
> > > > > #define ERANGE          34      /* Math result not representable */
> > > > > 
> > > > > Now the weird part...when I remove all the above libs above, the mount
> > > > > command works. I know that there are ceph.ko modules in the Ubuntu
> > > > > filesystems DIR, and that Ubuntu comes with some understanding of how
> > > > > to mount a cephfs system.  So, that explains how it can mount
> > > > > cephfs...but, what I don't understand is why I'm getting that -34
> > > > > error with the 14.2.5 and 14.2.6 libs installed. I didn't have this
> > > > > issue with 14.2.3 or 14.2.4.
> > > > 
> > > > This sounds like a regression in mount.ceph, probably due to something
> > > > that went in for v14.2.5. I can reproduce the problem on Fedora, and I
> > > > think it has something to do with the very long username you're using.
> > > > 
> > > > I'll take a closer look and let you know. Stay tuned.
> > > > 
> > > 
> > > I think I see the issue. The SECRET_OPTION_BUFSIZE is just too small for
> > > your use case. We need to make that a little larger than the largest
> > > name= parameter can be. Prior to v14.2.5, it was ~1000 bytes, but I made
> > > it smaller in that set thinking that was too large. Mea culpa.
> > > 
> > > The problem is determining how big that size can be. AFAICT EntityName
> > > is basically a std::string in the ceph code, which can be an arbitrary
> > > size (up to 4g or so).
> 
> It's just that you made SECRET_OPTION_BUFSIZE account precisely for
> "secret=<base64 secret>", but it can also be "key=<username>".
> 
> I don't think there is much of a problem.  Defining it back to ~1000 is
> guaranteed to work.  Or we could remove it and just compute the size of
> secret_option exactly the same way as get_secret_option() does it:
> 
>   strlen(cmi->cmi_secret) + strlen(cmi->cmi_name) + 7 + 1
> 

Yeah, it's not hard to do a simple fix like that, but I opted to rework
the code to just safe_cat the secret option string(s) directly into the 
options buffer.

That eliminates some extra copies of this info and the need for an
arbitrary limit altogether. It also removes a chunk of code that doesn't
really need to be in the common lib.

See:

    https://github.com/ceph/ceph/pull/32706

Aaron, if you have a way to build and test this, it'd be good if you
could confirm that it fixes the problem for you.
-- 
Jeff Layton <jlayton@xxxxxxxxxx>

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