Re: [Qemu-block] [PATCH V4] block/iscsi: allow caching of the allocation map
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
Re: [Qemu-block] [PATCH V4] block/iscsi: allow caching of the allocation map
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) 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. In addition, there is some code duplication so put these computations in two variables. Thanks! Paolo > +} > + > +if (iscsilun->allocmap_valid == NULL) { > +return; > +} > +if (valid) { > +if (nb_clusters > 0) { > +bitmap_set(iscsilun->allocmap_valid, cluster_num, nb_clusters); > +} > +} else { > +bitmap_clear(iscsilun->allocmap_valid, > + sector_num / iscsilun->cluster_sectors, > + DIV_ROUND_UP(nb_sectors, iscsilun->cluster_sectors)); > +}