Re: [Qemu-devel] [PATCH V7 0/8] add internal snapshot support at block device level

[Kevin Wolf]

Am 07.08.2013 um 05:00 hat Wenchao Xia geschrieben:
>   This series brings internal snapshot support at block devices level, now we
> have two three methods to do block snapshot lively: 1) backing chain,
> 2) internal one and 3) drive-back up approach.
> 
> Comparation:
>              Advantages:                            Disadvantages:
> 1)    delta data, taken fast, export, size        performance, delete slow.
> 2)  taken fast, delete fast, performance, size       delta data, format
> 3)      performance, export, format      taken slow, delta data, size, host 
> I/O
> 
>   I think in most case, saving vmstate in an standalone file is better than
> saving it inside qcow2, So suggest treat internal snapshot as block level
> methods and not encourage user to savevm in qcow2 any more.
> 
> Implemention details:
>   To avoid trouble, this serial have hide ID in create interfaces, this make
> sure no chaos of ID and name will be introduced by these interfaces.
>   There is one patch may be common to Pavel's savvm transaction, patch 1/11,
> others are not quite related. Patch 1/11 will not set errp when no snapshot
> find, since patch 3/11 need to distinguish real error case.
> 
> Next steps to better full VM snapshot:
>   Improve internal snapshot's export capability.
>   Better vmstate saving.
> 
>   Thanks Kevin to give advisement about how add it in qmp_transaction, oldest
> version comes drom Dietmar Maurer.

This series needs to be rebased. The last patch (qemu-iotests) doesn't
apply any more because other tests were added in the meantime, and when
applying only the code changes, it fails to compile:

blockdev.c: In function 'internal_snapshot_prepare':
blockdev.c:1040:5: error: implicit declaration of function 'qemu_get_clock_ns' 
[-Werror=implicit-function-declaration]
blockdev.c:1040:5: error: nested extern declaration of 'qemu_get_clock_ns' 
[-Werror=nested-externs]
blockdev.c:1040:43: error: 'vm_clock' undeclared (first use in this function)
blockdev.c:1040:43: note: each undeclared identifier is reported only once for 
each function it appears in

Kevin