On 18/07/2016 09:55, Peter Lieven wrote:
> Am 16.07.2016 um 15:38 schrieb Paolo Bonzini:
>>
>> On 30/06/2016 13:07, Peter Lieven wrote:
>>> +static void
>>> +iscsi_allocmap_update(IscsiLun *iscsilun, int64_t sector_num,
>>> + int nb_sectors, bool allocated, bool valid)
>>> {
>>> int64_t cluster_num, nb_clusters;
>>> - if (iscsilun->allocationmap == NULL) {
>>> +
>>> + if (iscsilun->allocmap == NULL) {
>>> return;
>>> }
>>> cluster_num = DIV_ROUND_UP(sector_num, iscsilun->cluster_sectors);
>>> nb_clusters = (sector_num + nb_sectors) /
>>> iscsilun->cluster_sectors
>>> - cluster_num;
>>> - if (nb_clusters > 0) {
>>> - bitmap_clear(iscsilun->allocationmap, cluster_num,
>>> nb_clusters);
>>> + if (allocated) {
>>> + bitmap_set(iscsilun->allocmap,
>>> + sector_num / iscsilun->cluster_sectors,
>>> + DIV_ROUND_UP(nb_sectors,
>>> iscsilun->cluster_sectors));
>>> + } else if (nb_clusters > 0) {
>>> + bitmap_clear(iscsilun->allocmap, cluster_num, nb_clusters);
>> I'm sorry for the delay in review, but this is still wrong.
>>
>> Suppose cluster_sectors is 2, sector_num = 1, nb_sectors = 6:
>>
>> 0--.--2--.--4--.--6--.--8
>> |_________________|
>>
>> Here in the "mark unallocated" case you want to set 2..6, i.e.
>> cluster_num=2, nb_clusters=2. This is right.
>>
>> 0--.--2--.--4--.--6--.--8
>> xxx|___________|xxx (x = shrunk)
>
> cluster_num = 1 and nb_clusters = 2
>
>>
>> In the "mark allocated" case, instead, you want to set 0..8, i.e.
>> cluster_num=0, nb_clusters=4.
>>
>> 0--.--2--.--4--.--6--.--8
>> <--|_________________|--> (<--> = expanded)
>>
>> Instead you are setting nb_clusters=3, so that 6..8 is not marked
>> allocated and reading 6..7 will return zeroes:
>>
>> 0--.--2--.--4--.--6--.--8
>> <--|______________|!!! (! = wrong)
>>
>> Instead you need to use
>>
>> DIV_ROUND_UP(sector_num + nb_sectors, ...)
>> - sector_num / iscsilun->cluster_sectors
>>
>> which does the rounding correctly.
>
> Right, but this has been wrong even in the currently active version.
>
> So I would propose to send 2 patches.
>
> 1) fix the rounding in the old version cc'ing qemu-stable
> 2) rebase the new patch on top of that.
That's okay.
Paolo
