Messages in this thread | | | Date | Sat, 20 Mar 2004 18:56:52 +0100 | From | Andrea Arcangeli <> | Subject | Re: can device drivers return non-ram via vm_ops->nopage? |
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On Sat, Mar 20, 2004 at 09:39:51AM -0800, Linus Torvalds wrote: > > > On Sat, 20 Mar 2004, Andrea Arcangeli wrote: > > > > The only bugreport I've got so far for the latest anon_vma code is from > > Jens, and it's a device driver bug in my opinion, but I'd like to have a > > definitive confirmation from you about the ->nopage API. > > I'd say that this is definitely a driver bug. > > If a driver wants to map non-RAM pages, that's perfectly ok, but it MUST > NOT happen through "nopage()". The driver should map them with > "remap_page_range()", and thus never take a page fault for such pages at > all. > > There is no reason to ever lazily map non-RAM pages - clearly they aren't > using any "real memory", so there is no reason to not fill the page tables > at mmap() time. > > In other words, the driver is horribly broken.
thanks for the clarification.
At the moment I'm not sure anymore if this was non-ram or a VM_FAULT_SIGBUS because I noticed I was doing BUG_ON(!pfn_valid) _before_ checking new_page == VM_FAULT_SIGBUS. Though my theory about do_no_page working fine with non-ram page_t with >=128m machines up to 2.6.4 still holds, and it's not obvious that Jens triggered a SIGBUS either. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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