From: Kevin Wolf <kwolf@redhat.com>
To: Max Reitz <mreitz@redhat.com>
Cc: John Snow <jsnow@redhat.com>,
qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 0/2] block: Let blockdev-create return 0 on success
Date: Mon, 2 Sep 2019 15:32:20 +0200 [thread overview]
Message-ID: <20190902133219.GG13140@localhost.localdomain> (raw)
In-Reply-To: <20190823184733.18929-1-mreitz@redhat.com>
Am 23.08.2019 um 20:47 hat Max Reitz geschrieben:
> Jobs are expected to return 0 on success. .bdrv_co_create() on the
> other hand is a block layer function, and as such returns a
> non-negative value on success.
I don't agree that >= 0 is the block layer way. The block layer uses
0/-errno for the largest part of its interfaces; and I think the
BlockDriver callbacks might even be consistent in this. Of course, we
never documented this anywhere, maybe we should...
The only historical exceptions I'm aware of are blk/bdrv_pread/pwrite(),
which return the byte count instead of 0. They should be fixed
eventually, but it just never seemed important enough, even though it
did cause bugs every now and then.
> blockdev_create_run() should translate between the two (patch 1).
>
> Without patch 1, blockdev-create is likely to fail for VPC images.
> Hence patch 2.
I'd argue this is a VPC bug. In the success path, it shouldn't return
ret as it happens to be at the end (it comes from bdrv_pwrite()), but
set it to 0 right before the 'fail:' label.
This is really a regression Jeff introduced in commit fef6070eff2,
though the bug was only latent then (five years ago).
Kevin
prev parent reply other threads:[~2019-09-02 13:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-23 18:47 [Qemu-devel] [PATCH 0/2] block: Let blockdev-create return 0 on success Max Reitz
2019-08-23 18:47 ` [Qemu-devel] [PATCH 1/2] " Max Reitz
2019-08-23 18:47 ` [Qemu-devel] [PATCH 2/2] iotests: Test blockdev-create for vpc Max Reitz
2019-08-27 21:15 ` John Snow
2019-08-27 21:15 ` [Qemu-devel] [PATCH 0/2] block: Let blockdev-create return 0 on success John Snow
2019-09-02 13:32 ` Kevin Wolf [this message]
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