On Wed, 28 Mar 2018 10:36:38 +0800 Dong Jia Shi <bjsdjshi@xxxxxxxxxxxxxxxxxx> wrote: > * Cornelia Huck <cohuck@xxxxxxxxxx> [2018-03-27 12:01:27 +0200]: > > [...] > > > > > > > > > So, basically everything is filled by pfn_array_alloc_pin()? > > > Yes. > > > > > > > Should we expect a clean struct pfn_array handed in by the caller, > > > > then (not just pa_nr == 0)? > > > The current idea is: > > > - It is a clean struct that pfn_array_alloc_pin() expects from its > > > caller. > > > - pfn_array_alloc_pin() and pfn_array_unpin_free() should be used in > > > pair. They are the only functions those change the values of the > > > elements of a pfn_array struct. > > > - Caller of pfn_array_alloc_pin() should either hand in a new allocated > > > pfn_array (zeroed out), or a freed-after-used one. > > > - So using pa_nr == 0, is enough to identify all the good cases. > > > [We set pa_nr to 0 in pfn_array_unpin_free().] > > > > > > Validating all of the elements only helps when there is case that a > > > caller breaks the usage rule of these interfaces - the caller itself > > > assigns values for pfn_pa elements directly... I don't think we allow > > > this to happen. > > > > > > So I think the current logic is fine. > > > > Yes, I think it is fine -- I was mainly wondering whether we wanted > > more sanity checks. > > > Ok. > Check on (pa->pa_iova_pfn != NULL) could be added. It's easy to do so. > Check on pa->pa_iova doesn't make sense, since its value will be > re-assigned anyway. > Check on pa->pa_pfn doesn't make sense, since we treat it as a pointer > that points to part of the memory area that was pointed by > pa->pa_iova_pfn. And we will re-assign it with new pa->pa_iova_pfn > value. Yeah, so additional checks are probably not very useful. > > > > > > > > > > > > Would it make sense to describe the contents of the struct pfn_array > > > > fields at the struct's definition instead? You could then shorten the > > > > description here to "we expect pa_nr == 0, any field in this structure > > > > will be filled in by this function". > > > Sounds good! > > > Do you want a separated patch for this, or I do this change on this > > > patch? Either will be ok with me. > > > > Perhaps as an additional patch in front of this one? > > > It's doable. I will do that. > Cool, thx!
