Re: [Qemu-devel] [PATCH v6 8/9] qcow2: skip writing zero buffers to empty COW areas

2018-01-17 Thread Anton Nefedov
On 16/1/2018 7:11 PM, Alberto Garcia wrote: On Tue 16 Jan 2018 02:04:29 PM CET, Anton Nefedov wrote: iotest 060: write to the discarded cluster does not trigger COW anymore. so, break on write_aio event instead, will work for the test (but write won't fail anymore, so update reference

Re: [Qemu-devel] [PATCH v6 8/9] qcow2: skip writing zero buffers to empty COW areas

2018-01-16 Thread Alberto Garcia
On Tue 16 Jan 2018 02:04:29 PM CET, Anton Nefedov wrote: > iotest 060: > write to the discarded cluster does not trigger COW anymore. > so, break on write_aio event instead, will work for the test > (but write won't fail anymore, so update reference output) I'm wondering about this. The reason

[Qemu-devel] [PATCH v6 8/9] qcow2: skip writing zero buffers to empty COW areas

2018-01-16 Thread Anton Nefedov
If COW areas of the newly allocated clusters are zeroes on the backing image, efficient bdrv_write_zeroes(flags=BDRV_REQ_ALLOCATE) can be used on the whole cluster instead of writing explicit zero buffers later in perform_cow(). iotest 060: write to the discarded cluster does not trigger COW