linux-kernel - Re: [RFC PATCH v3] ceph: add new obj copy OSD Op

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Message-ID: <20191120095536.GA13949@hermes.olymp>
Date:   Wed, 20 Nov 2019 09:55:36 +0000
From:   Luis Henriques <lhenriques@...e.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        "Yan, Zheng" <zyan@...hat.com>,
        Gregory Farnum <gfarnum@...hat.com>,
        ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3] ceph: add new obj copy OSD Op

On Mon, Nov 18, 2019 at 02:05:51PM +0000, Luis Henriques wrote:
> On Mon, Nov 18, 2019 at 08:12:39AM -0500, Jeff Layton wrote:
> > On Mon, 2019-11-18 at 12:09 +0000, Luis Henriques wrote:
> > > Hi,
> > > 
> > > Before going ahead with a pull-request for ceph I would like to make sure
> > > we're all on the same page regarding the final fix for this problem.
> > > Thus, following this email, I'm sending 2 patches: one for ceph OSDs and
> > > the another for the kernel client.
> > > 
> > > * osd: add new 'copy-from-notrunc' operation
> > >   This patch shall be applied to ceph master after reverting commit
> > >   ba152435fd85 ("osd: add flag to prevent truncate_seq copy in copy-from
> > >   operation").  It adds a new operation that will be exactly the same as
> > >   the original 'copy-from' operation, but with the extra 2 parameters
> > >   (truncate_{seq,size})
> > > 
> > > * ceph: switch copy_file_range to 'copy-from-notrunc' operation
> > >   This will make the kernel client use the new OSD op in
> > >   copy_file_range.  One extra thing that could probably be added is
> > >   changing the mount options to NOCOPYFROM if the first call to
> > >   ceph_osdc_copy_from() fails.
> > > 
> > 
> > I probably wouldn't change the mount options to be different from what
> > was initially specified. How about just disable copy_file_range
> > internally for that superblock, and then pr_notice a message that says
> > that copy_file_range is being autodisabled. If they mount with '-o
> > nocopyfrom' that will make the warning go away.
> 
> Ok, that makes sense.  I'll include this in the next rev, which will
> probably be sent only after the pull-request for ceph goes in (assuming
> the OSD patch won't need any major rework).

FYI, yesterday I created the pull-request for this [1].  I thought I had
also sent an email to this thread, but I guess I didn't... so, here it
is :-) 

[1] https://github.com/ceph/ceph/pull/31728

Cheers,
--
Luís

> 
> > > Does this look good, or did I missed something from the previous
> > > discussion?
> > > 
> > > (One advantage of this approach: the OSD patch can be easily backported!)
> > > 
> > 
> > Yep, I think this looks like a _much_ simpler approach to the problem.
> 
> Agreed!
> 
> Cheers,
> --
> Luís