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. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
