From: patchon <martinsson.patrik(a)gmail.com&gt; These commits simply adds the '--shrink' flag to the blockresize command to prevent accidental shrinking of a block device. This behaviour is already present on the vol-resize command and it makes sense to mimic that behaviour. Only implemented in the qemu-driver atm. Signed-off-by: Patrik Martinsson <martinsson.patrik(a)gmail.com&gt; --- src/qemu/qemu_driver.c | 15 ++++++++++++++- tools/virsh-domain.c | 7 +++++++ tools/virsh.pod | 9 ++++++++- 3 files changed, 29 insertions(+), 2 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 95fe844c34..4e34eec796 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -11265,8 +11265,10 @@ qemuDomainBlockResize(virDomainPtr dom, char *device = NULL; const char *nodename = NULL; virDomainDiskDefPtr disk = NULL; + virDomainBlockInfo info; - virCheckFlags(VIR_DOMAIN_BLOCK_RESIZE_BYTES, -1); + virCheckFlags(VIR_DOMAIN_BLOCK_RESIZE_BYTES | + VIR_STORAGE_VOL_RESIZE_SHRINK, -1); /* We prefer operating on bytes. */ if ((flags & VIR_DOMAIN_BLOCK_RESIZE_BYTES) == 0) { @@ -11279,6 +11281,9 @@ qemuDomainBlockResize(virDomainPtr dom, size *= 1024; } + if (virDomainGetBlockInfo(dom, path, &info, 0) < 0) + goto cleanup; + if (!(vm = qemuDomainObjFromDomain(dom))) goto cleanup; @@ -11299,6 +11304,14 @@ qemuDomainBlockResize(virDomainPtr dom, goto endjob; } + if (size < info.capacity && + !(flags & VIR_STORAGE_VOL_RESIZE_SHRINK)) { + virReportError(VIR_ERR_INVALID_ARG, "%s", + _("Can't shrink capacity below current " + "capacity unless shrink flag explicitly specified")); + goto endjob; + } + /* qcow2 and qed must be sized on 512 byte blocks/sectors, * so adjust size if necessary to round up. */ diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c index fbfdc09c0d..a67ee35428 100644 --- a/tools/virsh-domain.c +++ b/tools/virsh-domain.c @@ -2920,6 +2920,10 @@ static const vshCmdOptDef opts_blockresize[] = { .flags = VSH_OFLAG_REQ, .help = N_("New size of the block device, as scaled integer (default KiB)") }, + {.name = "shrink", + .type = VSH_OT_BOOL, + .help = N_("allow the resize to shrink the volume") + }, {.name = NULL} }; @@ -2938,6 +2942,9 @@ cmdBlockresize(vshControl *ctl, const vshCmd *cmd) if (vshCommandOptScaledInt(ctl, cmd, "size", &size, 1024, ULLONG_MAX) < 0) return false; + if (vshCommandOptBool(cmd, "shrink")) + flags |= VIR_STORAGE_VOL_RESIZE_SHRINK; + /* Prefer the older interface of KiB. */ if (size % 1024 == 0) size /= 1024; diff --git a/tools/virsh.pod b/tools/virsh.pod index cf2798e71a..96387127d6 100644 --- a/tools/virsh.pod +++ b/tools/virsh.pod @@ -1027,7 +1027,7 @@ I<bandwidth> specifies copying bandwidth limit in MiB/s. For further information on the I<bandwidth> argument see the corresponding section for the B<blockjob> command. -=item B<blockresize> I<domain> I<path> I<size> +=item B<blockresize> I<domain> I<path> I<--size> I<--shrink> Resize a block device of domain while the domain is running, I<path> specifies the absolute path of the block device; it corresponds @@ -1040,6 +1040,13 @@ I<size> is a scaled integer (see B<NOTES> above) which defaults to KiB "B" to get bytes (note that for historical reasons, this differs from B<vol-resize> which defaults to bytes without a suffix). +Attempts to shrink the block device will fail unless I<--shrink> is present. +The I<capacity> cannot be negative since the given capacity is the absolute +size of the block device. Always exercise caution when shrinking a block device. +B<Also note> that it is up to the driver to implement the check if shrinking +should be allowed or not depending on if I<--shrink> is set. So far only the +qemu-driver does this. + =item B<console> I<domain> [I<devname>] [I<--safe>] [I<--force>] Connect the virtual serial console for the guest. The optional -- 2.23.0

On Tue, Oct 15, 2019 at 10:46 PM Cole Robinson <crobinso(a)redhat.com&gt; wrote: I agree that an options should be added here to avoid undesirable disk shrinking. Because I have broken guest OS image for several times due to the shrinking of blockresize. changes the behavior of blockresize API and may cause unexpected error in uplayer products. It is better to add the check to codes of **virsh** to avoid undesirable shrinking in cmdline user. And we can use '--force' to make blockresize always. The procedure will be: if (new size < capacity && no --force) print error("Can't shrink capacity below current unless --force specified") else call blockresize And also we can add comments to blockresize API to avoid uplayer use undesirable disk shrinking. -- Best regards, ----------------------------------- Han Han Quality Engineer Redhat. Email: hhan(a)redhat.com Phone: +861065339333