On Thu, Oct 4, 2018 at 3:45 AM Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> wrote: > > On Wed, Oct 03, 2018 at 01:00:03PM -0700, Matthew Wilcox wrote: > > On Thu, Oct 04, 2018 at 12:28:54AM +0530, Souptick Joarder wrote: > > > These are the approaches which could have been taken to handle > > > this scenario - > > > > > > * Replace vm_insert_page with vmf_insert_page and then write few > > > extra lines of code to convert VM_FAULT_CODE to errno which > > > makes driver users more complex ( also the reverse mapping errno to > > > VM_FAULT_CODE have been cleaned up as part of vm_fault_t migration , > > > not preferred to introduce anything similar again) > > > > > > * Maintain both vm_insert_page and vmf_insert_page and use it in > > > respective places. But it won't gurantee that vm_insert_page will > > > never be used in #PF context. > > > > > > * Introduce a similar API like vm_insert_page, convert all non #PF > > > consumer to use it and finally remove vm_insert_page by converting > > > it to vmf_insert_page. > > > > > > And the 3rd approach was taken by introducing vm_insert_kmem_page(). > > > > > > In short, vmf_insert_page will be used in page fault handlers > > > context and vm_insert_kmem_page will be used to map kernel > > > memory to user vma outside page fault handlers context. > > > > As far as I can tell, vm_insert_kmem_page() is line-for-line identical > > with vm_insert_page(). Seriously, here's a diff I just did: > > > > -static int insert_page(struct vm_area_struct *vma, unsigned long addr, > > - struct page *page, pgprot_t prot) > > +static int insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, > > + struct page *page, pgprot_t prot) > > - /* Ok, finally just insert the thing.. */ > > -int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, > > +int vm_insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, > > - return insert_page(vma, addr, page, vma->vm_page_prot); > > + return insert_kmem_page(vma, addr, page, vma->vm_page_prot); > > -EXPORT_SYMBOL(vm_insert_page); > > +EXPORT_SYMBOL(vm_insert_kmem_page); > > > > What on earth are you trying to do? > > Reading the commit log, it seems that the intention is to split out > vm_insert_page() used outside of page-fault handling with the use > within page-fault handling, so that different return codes can be > used. > > I don't see that justifies the code duplication - can't > vm_insert_page() and vm_insert_kmem_page() use the same mechanics > to do their job, and just translate the error code from the most- > specific to the least-specific error code? Do we really need two > copies of the same code just to return different error codes. Sorry about it. can I take below approach in a patch series -> create a wrapper function vm_insert_kmem_page using vm_insert_page. Convert all the non #PF users to use it. Then make vm_insert_page static and convert inline vmf_insert_page to caller.
