[Gluster-users] Invalid atime with gluster-NFS

[Eivind Sarto]

I filed a bug and attached this proposed patch last week.
I have tested it with both gluster-NFS and Ganesha and it appears to fix
the problem.

On Fri, Dec 2, 2016 at 10:19 PM, Niels de Vos <ndevos at redhat.com> wrote:

> On Thu, Dec 01, 2016 at 05:04:06PM -0800, Eivind Sarto wrote:
> > Overwriting an existing file with O_TRUNC will yield an incorrect atime.
> > Example:
> >
> > root at vsan123:~# cp /vmlinuz /nfs
> > root at vsan123:~# stat /nfs/vmlinuz
> >   File: ‘/nfs/vmlinuz’
> >   Size: 6565968         Blocks: 12825      IO Block: 1048576 regular file
> > Device: 25h/37d Inode: 10266595591654252930  Links: 1
> > Access: (0600/-rw-------)  Uid: (    0/    root)   Gid: (    0/    root)
> > Access: 2016-12-01 16:39:48.000000000 -0800
> > Modify: 2016-12-01 16:39:48.235275472 -0800
> > Change: 2016-12-01 16:39:48.239275472 -0800
> >  Birth: -
> > root at vsan123:~# dd if=/vmlinuz of=/nfs/vmlinuz bs=64k conv=nocreat
> > 100+1 records in
> > 100+1 records out
> > 6565968 bytes (6.6 MB) copied, 0.0271412 s, 242 MB/s
> > root at vsan123:~# stat /nfs/vmlinuz
> >   File: ‘/nfs/vmlinuz’
> >   Size: 6565968         Blocks: 12825      IO Block: 1048576 regular file
> > Device: 25h/37d Inode: 10266595591654252930  Links: 1
> > Access: (0600/-rw-------)  Uid: (    0/    root)   Gid: (    0/    root)
> > Access: 1969-12-31 16:00:00.000000000 -0800
> > Modify: 2016-12-01 16:39:57.923275920 -0800
> > Change: 2016-12-01 16:39:57.923275920 -0800GF_SET_ATTR_MTIME
> >  Birth: -
> >
> > The Access time has been set to zero (or 1970 PST in my case)
> >
> > This appears to happen in all versions of gluster.  I think the problem
> can
> > actually be blamed on posix_setattr().  If one does a FOP_SETATTR and
> only
> > passes the GF_SET_ATTR_MTIME flag, posix_setattr() will blindly call
> > lutimes() to modify both atime+mtime and atime gets set to 0.
> > I think the solution would be to modify posix_setattr() to write back
> > original atime/mtime if one of the flags are not specified.
>
> Thanks for reporting this! Could you file a bug on
> https://bugzilla.redhat.com/enter_bug.cgi?product=GlusterFS as well?
> Just copy/paste the contents of the email in the report and let us know
> the URL of the bug that you created. We'll clone the bug for all
> actively maintained versions after that.
>
> The attached patch has been completely untested, but it should resolve
> the problem. I'd appreciate it if you can give that a try and report
> results.
>
> > I have also seen NFS-Ganesha end up with a zero atime, but it does happen
> > not for the example above on Ganesha.  Ganesha probably does something
> > similar someplace in its code where only GF_SET_ATTR_MTIME is being set.
> > But, I cannot remember exactly what caused the zero atime on Ganesha.
>
> NFS-Ganesha uses libgfapi and the library makes it possible to only pass
> atime or mtime in glfs_h_setattrs(). Possibly NFS-Ganesha internally
> maintains the atime+mtime combination, or the (Linux?) NFS-client
> handles it differently over NFSv4. In any case, the attached patch
> should also prevent this from happening with NFS-Ganesha.
>
> > All other code in gluster, other than nfsserver, sets both ATIME and
> MTIME
> > when doing an FOP_SETATTR.
>
> Good to check that, it would give one possible explanation why this is
> not happening over FUSE mounts.
>
> Thanks again,
> Niels
>
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