On Fri, Aug 19, 2022 at 04:45:05PM +0100, Matthew Wilcox wrote: > On Fri, Aug 19, 2022 at 12:53:32PM +0200, Uladzislau Rezki wrote: > > Looks pretty straightforward. One thing though, if we can combine it > > together with vmap(), since it is a copy paste in some sense, say to > > have something __vmap() to reuse it in the vmap_folio() and vmap(). > > > > But that is just a thought. > > Thanks for looking it over! > You are welcome. > > Combining it with vmap() or vm_map_ram() is tricky. Today, we assume > that each struct page pointer refers to exactly PAGE_SIZE bytes, so if > somebody calls alloc_pages(GFP_COMPOUND, 4) and then passes the head > page to vmap(), only that one page gets mapped. I don't know whether > any current callers depend on that behaviour. > > Now that I look at the future customers of this, I think I erred in basing > this on vmap(), it looks like vm_map_ram() is preferred. So I'll redo > based on vm_map_ram(). > Indeed, the vmap code has no knowledge about comound pages. You can add me to CC, so i can have a look on it to help out with it if there will be a need. -- Uladzislau Rezki
