On Thu, 10 Dec 2015 19:21:42 -0800 Andy Lutomirski <[email protected]> wrote:
> From: Andy Lutomirski <[email protected]> > > Requiring special mappings to give a list of struct pages is > inflexible: it prevents sane use of IO memory in a special mapping, > it's inefficient (it requires arch code to initialize a list of > struct pages, and it requires the mm core to walk the entire list > just to figure out how long it is), and it prevents arch code from > doing anything fancy when a special mapping fault occurs. > > Add a .fault method as an alternative to filling in a .pages array. > > ... > > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -568,10 +568,27 @@ static inline void clear_tlb_flush_pending(struct > mm_struct *mm) > } > #endif > > +struct vm_fault; > + > struct vm_special_mapping > { We may as well fix the code layout while we're in there. > - const char *name; > + const char *name; /* The name, e.g. "[vdso]". */ > + > + /* > + * If .fault is not provided, this is points to a s/is// > + * NULL-terminated array of pages that back the special mapping. > + * > + * This must not be NULL unless .fault is provided. > + */ > struct page **pages; > + > + /* > + * If non-NULL, then this is called to resolve page faults > + * on the special mapping. If used, .pages is not checked. > + */ > + int (*fault)(const struct vm_special_mapping *sm, > + struct vm_area_struct *vma, > + struct vm_fault *vmf); > }; > > enum tlb_flush_reason { > diff --git a/mm/mmap.c b/mm/mmap.c > index 2ce04a649f6b..f717453b1a57 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -3030,11 +3030,16 @@ static int special_mapping_fault(struct > vm_area_struct *vma, > pgoff_t pgoff; > struct page **pages; > > - if (vma->vm_ops == &legacy_special_mapping_vmops) > + if (vma->vm_ops == &legacy_special_mapping_vmops) { > pages = vma->vm_private_data; > - else > - pages = ((struct vm_special_mapping *)vma->vm_private_data)-> > - pages; > + } else { > + struct vm_special_mapping *sm = vma->vm_private_data; > + > + if (sm->fault) > + return sm->fault(sm, vma, vmf); > + > + pages = sm->pages; > + } > > for (pgoff = vmf->pgoff; pgoff && *pages; ++pages) > pgoff--; Otherwise looks OK. I'll assume this will be merged via an x86 tree. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
