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From: Jeff Cody <jcody@redhat.com>
To: Eric Blake <eblake@redhat.com>
Cc: kwolf@redhat.com, benoit.canet@irqsave.net, pkrempa@redhat.com,
	famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com
Subject: Re: [Qemu-devel] [PATCH 1/5] block: Auto-generate node_names for each BDS entry
Date: Thu, 15 May 2014 14:41:03 -0400	[thread overview]
Message-ID: <20140515184103.GM8452@localhost.localdomain> (raw)
In-Reply-To: <5374E445.9070609@redhat.com>

On Thu, May 15, 2014 at 09:59:01AM -0600, Eric Blake wrote:
> On 05/14/2014 09:20 PM, Jeff Cody wrote:
> > Currently, node_name is only filled in when done so explicitly by the
> > user.  If no node_name is specified, then the node name field is not
> > populated.
> > 
> > If node_names are automatically generated when not specified, that means
> > that all block job operations can be done by reference to the unique
> > node_name field.  This eliminates ambiguity in filename pathing
> > (relative filenames, or file descriptors, symlinks, mounts, etc..) that
> > qemu currently needs to deal with.
> > 
> > If a node name is specified, then it will not be automatically
> > generated for that BDS entry.
> > 
> > If it is automatically generated, it will be prefaced with "__qemu##",
> > followed by 8 characters of a unique number, followed by 8 random
> > ASCII characters in the range of 'A-Z'.  Some sample generated node-name
> > strings:
> >     __qemu##00000000IAIYNXXR
> >     __qemu##00000002METXTRBQ
> >     __qemu##00000001FMBORDWG
> > 
> > The prefix is to aid in identifying it as a qemu-generated name, the
> > numeric portion is to guarantee uniqueness in a given qemu session, and
> > the random characters are to further avoid any accidental collisions
> > with user-specified node-names.
> > 
> > Signed-off-by: Jeff Cody <jcody@redhat.com>
> > ---
> >  block.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> This patch feels incomplete.  We probably also ought to modify
> qapi-schema.json to make BlockDeviceInfo's output of 'node-name' by
> unconditional (as an output-only struct, changing from optional to
> mandatory is a safe change for back-compat API considerations); which
> implies further modifying code to get rid of has_node_name arguments in
> all places that generate BlockDeviceInfo details.

I think it should be a separate patch (but still in this series).
Strictly speaking, this patch doesn't force the argument to be
mandatory, the value just happens to always be populated now.

> See also my thoughts on patch 5/5 - can this patch be rebased to be LAST
> in the series, rather than first, so that it serves as a reliable
> witness that everything else related to block operations on node-names
> is complete?
>
How about this becomes the penultimate patch, and the patch to make
BlockDeviceInfo's node-name field to be unconditional becomes the last
patch?

The only thing I don't like about moving this further back in the
patch series is it makes the earlier patches untestable; I can't
easily test the usage of the node-names for various intermediate BDS
because they don't have node-names set.  So that means I'll just need
to rebase the patches prior to sending.  So let me revise my above
statement - how about this patch stays at the beginning, which makes
development / testing easier, with the patch that modifies
BlockDeviceInfo as the final (not including tests) patch?

  reply	other threads:[~2014-05-15 18:41 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-15  3:20 [Qemu-devel] [PATCH 0/5] block: Modify block-commit to use node-names Jeff Cody
2014-05-15  3:20 ` [Qemu-devel] [PATCH 1/5] block: Auto-generate node_names for each BDS entry Jeff Cody
2014-05-15 11:58   ` Benoît Canet
2014-05-15 12:06     ` Jeff Cody
2014-05-15 12:32       ` Benoît Canet
2014-05-15 12:37         ` Jeff Cody
2014-05-15 14:11   ` Eric Blake
2014-05-15 15:59   ` Eric Blake
2014-05-15 18:41     ` Jeff Cody [this message]
2014-05-15 19:12       ` Eric Blake
2014-05-16  9:39       ` Kevin Wolf
2014-05-16 11:35         ` Jeff Cody
2014-05-16 12:47           ` Eric Blake
2014-05-16 17:16             ` Kevin Wolf
2014-05-15  3:20 ` [Qemu-devel] [PATCH 2/5] block: add helper function to determine if a BDS is in a chain Jeff Cody
2014-05-15 11:48   ` Benoît Canet
2014-05-15 14:16   ` Eric Blake
2014-05-15 14:24     ` Kevin Wolf
2014-05-15 14:31     ` Jeff Cody
2014-05-15  3:20 ` [Qemu-devel] [PATCH 3/5] block: make 'top' argument to block-commit optional Jeff Cody
2014-05-15 11:47   ` Benoît Canet
2014-05-15 11:49     ` Jeff Cody
2014-05-15 15:07   ` Eric Blake
2014-05-15  3:20 ` [Qemu-devel] [PATCH 4/5] block: Accept node-name arguments for block-commit Jeff Cody
2014-05-15 12:09   ` Benoît Canet
2014-05-15 15:42   ` Eric Blake
2014-05-15 18:04     ` Jeff Cody
2014-05-15  3:20 ` [Qemu-devel] [PATCH 5/5] block: extend block-commit to accept a string for the backing file Jeff Cody
2014-05-15 12:26   ` Benoît Canet
2014-05-15 12:57     ` Eric Blake
2014-05-15 13:10       ` Jeff Cody
2014-05-15 13:14         ` Eric Blake
2014-05-15 16:06   ` Eric Blake
2014-05-15 18:22     ` Jeff Cody
2014-05-15 18:52       ` Eric Blake

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