On 09/19/2016 04:21 AM, Fam Zheng wrote:
> On Thu, 09/15 19:34, Denis V. Lunev wrote:
>> They should work very similar, covering same areas if backing store is
>> shorter than the image. This change is necessary for the followup patch
>> switching to bdrv_get_block_status_above() in mirror to avoid assert
>> in check_block.
>>
>> This change should be made very carefully. Let us assume that we have
>> top image and 2 backing stores L0->L1->L2.
> Stupid question: which one is top and which are backing?
L0 is top, L2 is at bottom.
>> L0: --------------
>> L1: -------
>> L2: -------=======
>> The data marked as '=' in L2 should not appear as BDRV_BLOCK_ALLOCATED
>> and we should return it as filled in L0 image with properly calculated
>> *pnum value.
> What '-', '=' and ' ' represent aren't immediately clear to me, could you put
> a
> legend in the message too? Something like:
>
> '-': allocated
> '=': unallocated
> ' ': beyong EOF
ok.
here '-' in unallocated
'=' is allocated.
virtual size of L1 image is shorter that L2 and L0, thus ' ' is beyond EOF.
Thank you, will rewrite today.
Den
>> Signed-off-by: Denis V. Lunev <d...@openvz.org>
>> CC: Stefan Hajnoczi <stefa...@redhat.com>
>> CC: Fam Zheng <f...@redhat.com>
>> CC: Kevin Wolf <kw...@redhat.com>
>> CC: Max Reitz <mre...@redhat.com>
>> CC: Jeff Cody <jc...@redhat.com>
>> ---
>> block/io.c | 25 ++++++++++++++++++++-----
>> 1 file changed, 20 insertions(+), 5 deletions(-)
>>
>> diff --git a/block/io.c b/block/io.c
>> index 420944d..067d465 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -1741,18 +1741,33 @@ static int64_t coroutine_fn
>> bdrv_co_get_block_status_above(BlockDriverState *bs,
>> BlockDriverState **file)
>> {
>> BlockDriverState *p;
>> - int64_t ret = 0;
>> + int64_t ret = 0, res = nb_sectors;
>>
>> assert(bs != base);
>> for (p = bs; p != base; p = backing_bs(p)) {
>> - ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum,
>> file);
>> - if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) {
>> - break;
>> + int sc;
>> + ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, &sc,
>> file);
>> + if (ret < 0) {
>> + return ret;
>> + } else if (ret & BDRV_BLOCK_ALLOCATED) {
>> + *pnum = sc;
>> + return ret;
>> + }
>> +
>> + if (res > sc && (p == bs || sector_num + sc < p->total_sectors)) {
>> + res = sc;
>> }
>> +
>> /* [sector_num, pnum] unallocated on this layer, which could be only
>> * the first part of [sector_num, nb_sectors]. */
>> - nb_sectors = MIN(nb_sectors, *pnum);
>> + nb_sectors = MIN(nb_sectors, sc);
>> +
>> + if (nb_sectors == 0) {
>> + break;
>> + }
>> }
>> +
>> + *pnum = res;
>> return ret;
>> }
>>
>> --
>> 2.7.4
>>
>>
