vm_insert_kmem_page is similar to vm_insert_page and will be used by drivers to map kernel (kmalloc/vmalloc/pages) allocated memory to user vma.
Previously vm_insert_page is used for both page fault handlers and outside page fault handlers context. When vm_insert_page is used in page fault handlers context, each driver have to map errno to VM_FAULT_CODE in their own way. But as part of vm_fault_t migration all the page fault handlers are cleaned up by using new vmf_insert_page. Going forward, vm_insert_page will be removed by converting it to vmf_insert_page. But their are places where vm_insert_page is used outside page fault handlers context and converting those to vmf_insert_page is not a good approach as drivers will end up with new VM_FAULT_CODE to errno conversion code and it will make each user more complex. So this new vm_insert_kmem_page can be used to map kernel memory to user vma outside page fault handler context. 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. We will slowly convert all the user of vm_insert_page to vm_insert_kmem_page after this API be available in linus tree. Signed-off-by: Souptick Joarder <[email protected]> --- include/linux/mm.h | 2 ++ mm/memory.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ mm/nommu.c | 7 ++++++ 3 files changed, 78 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index a61ebe8..5f42d35 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2477,6 +2477,8 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr); int remap_pfn_range(struct vm_area_struct *, unsigned long addr, unsigned long pfn, unsigned long size, pgprot_t); +int vm_insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page); int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *); int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn); diff --git a/mm/memory.c b/mm/memory.c index c467102..b800c10 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1682,6 +1682,75 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, return pte_alloc_map_lock(mm, pmd, addr, ptl); } +static int insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page, pgprot_t prot) +{ + struct mm_struct *mm = vma->vm_mm; + int retval; + pte_t *pte; + spinlock_t *ptl; + + retval = -EINVAL; + if (PageAnon(page)) + goto out; + retval = -ENOMEM; + flush_dcache_page(page); + pte = get_locked_pte(mm, addr, &ptl); + if (!pte) + goto out; + retval = -EBUSY; + if (!pte_none(*pte)) + goto out_unlock; + + get_page(page); + inc_mm_counter_fast(mm, mm_counter_file(page)); + page_add_file_rmap(page, false); + set_pte_at(mm, addr, pte, mk_pte(page, prot)); + + retval = 0; + pte_unmap_unlock(pte, ptl); + return retval; +out_unlock: + pte_unmap_unlock(pte, ptl); +out: + return retval; +} + +/** + * vm_insert_kmem_page - insert single page into user vma + * @vma: user vma to map to + * @addr: target user address of this page + * @page: source kernel page + * + * This allows drivers to insert individual kernel memory into a user vma. + * This API should be used outside page fault handlers context. + * + * Previously the same has been done with vm_insert_page by drivers. But + * vm_insert_page will be converted to vmf_insert_page and will be used + * in fault handlers context and return type of vmf_insert_page will be + * vm_fault_t type. + * + * But there are places where drivers need to map kernel memory into user + * vma outside fault handlers context. As vmf_insert_page will be restricted + * to use within page fault handlers, vm_insert_kmem_page could be used + * to map kernel memory to user vma outside fault handlers context. + */ +int vm_insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page) +{ + if (addr < vma->vm_start || addr >= vma->vm_end) + return -EFAULT; + if (!page_count(page)) + return -EINVAL; + if (!(vma->vm_flags & VM_MIXEDMAP)) { + BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem)); + BUG_ON(vma->vm_flags & VM_PFNMAP); + vma->vm_flags |= VM_MIXEDMAP; + } + return insert_kmem_page(vma, addr, page, vma->vm_page_prot); +} +EXPORT_SYMBOL(vm_insert_kmem_page); + /* * This is the old fallback for page remapping. * diff --git a/mm/nommu.c b/mm/nommu.c index e4aac33..153b8c8 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -473,6 +473,13 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, } EXPORT_SYMBOL(vm_insert_page); +int vm_insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page) +{ + return -EINVAL; +} +EXPORT_SYMBOL(vm_insert_kmem_page); + /* * sys_brk() for the most part doesn't need the global kernel * lock, except when an application is doing something nasty -- 1.9.1
