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Re: [Qemu-block] [PATCH 0/3] block/file-posix: File locking during creat
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-block] [PATCH 0/3] block/file-posix: File locking during creation |
Date: |
Mon, 23 Apr 2018 15:19:27 +0200 |
User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
On Sat 21 Apr 2018 12:09:10 AM CEST, Max Reitz wrote:
> Currently we do not take permissions on a file while it is being
> created. That is a bit sad. The simplest way to test this is the
> following:
>
> $ qemu-img create -f qcow2 foo.qcow2 64M
> Formatting 'foo.qcow2', fmt=qcow2 size=67108864 cluster_size=65536
> lazy_refcounts=off refcount_bits=16
> $ qemu-img convert -f qcow2 -O qcow2 foo.qcow2 foo.qcow2
> qemu-img: foo.qcow2: error while converting qcow2: Failed to get "write"
> lock
> Is another process using the image?
> $ qemu-img info foo.qcow2
> image: foo.qcow2
> file format: raw
> virtual size: 0 (0 bytes)
> disk size: 0
Not quite the same problem, but here's another example of QEMU creating
an image before checking if it can be created:
$ qemu-img create -o cluster_size=2M -f qcow2 img.qcow2 7E
Formatting 'img.qcow2', fmt=qcow2 size=8070450532247928832 encryption=off
cluster_size=2097152 lazy_refcounts=off refcount_bits=16
qemu-img: img.qcow2: The image size is too large for file format 'qcow2' (try
using a larger cluster size)
$ qemu-img info img.qcow2
image: img.qcow2
file format: qcow2
virtual size: 0 (0 bytes)
disk size: 6.0M
cluster_size: 2097152
Format specific information:
compat: 1.1
lazy refcounts: false
refcount bits: 16
corrupt: false
Berto