Re: [libvirt] [TCK PATCHv3] block devices: allow specification of size for safety
Eric Blake wrote:
I was getting failures of domain/103-blockdev-save-restore.t when
connecting as qemu:///session, since my uid could stat /dev/sdb but
not open it. That test now skips for unprivileged users, as well as
adds a layer of sanity checking against expected size to avoid
trashing the wrong device.
* conf/default.cfg (host_block_devices): Document optional size.
* lib/Sys/Virt/TCK.pm (get_host_block_device): If optional size is
supplied, skip a device that does not match. Also, avoid devices
that can't be opened.
---
Changes from v2:
+ guarantee that the device can be opened by the current user, even if
the .cfg file used the older path-only configuration
ACK.
+# Each block device is either a raw path
# /dev/vdb
+# or a path plus size in 1k blocks, as in /proc/partitions, to avoid
+# trashing the wrong device
+# {
+# path = /dev/disk/by-id/usb-Generic_Flash_Disk_9B46E3C5-0:0
Much improved example.
With by-id/ and the verbose name, there should be no problem.
+# size = 989184
+# }
...
- return
$self->config("host_block_devices/[$devindex]", undef);
+ my $device = $self->config("host_block_devices/[$devindex]/path",
undef);
+ my $kb_blocks = $self->config("host_block_devices/[$devindex]/size",
0);
+ my $match = 1;
+
+ $device ||= $self->config("host_block_devices/[$devindex]", undef);
+
+ # Filter out devices that the current user can't open.
+ sysopen(BLK, $device, O_RDONLY) or return undef;
+
+ if ($kb_blocks) {
+ $match = sysseek(BLK, 0, SEEK_END) == $kb_blocks * 1024;
+ }
+ close BLK;
+
+ return $match ? $device : undef;
}
That looks fine and correct.
You could move the $kb_blocks definition "down" to where used.
though there's a good argument for keeping it near the
other config-getting statement. Either way is fine.
However, I find it more readable to group the two $device-setting
statements together:
my $device = $self->config("host_block_devices/[$devindex]/path",
undef);
$device ||= $self->config("host_block_devices/[$devindex]", undef);
my $kb_blocks = $self->config("host_block_devices/[$devindex]/size",
0);
+ my $match = 1;
There is no reason to declare/set $match so early.
Move that down to where it's used.
Rather than an "if (...)" and a one-line {...} block,
I would write it this way: "syntax: less is always (more ;-) better"
my $match = 1;
$kb_blocks
and $match = sysseek(BLK, 0, SEEK_END) == $kb_blocks * 1024;