mm/frame_vector.c

   1 #include <linux/kernel.h>
   2 #include <linux/errno.h>
   3 #include <linux/err.h>
   4 #include <linux/mm.h>
   5 #include <linux/slab.h>
   6 #include <linux/vmalloc.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/sched.h>
   9
  10 /**
  11  * get_vaddr_frames() - map virtual addresses to pfns
  12  * @start:      starting user address
  13  * @nr_frames:  number of pages / pfns from start to map
  14  * @gup_flags:  flags modifying lookup behaviour
  15  * @vec:        structure which receives pages / pfns of the addresses mapped.
  16  *              It should have space for at least nr_frames entries.
  17  *
  18  * This function maps virtual addresses from @start and fills @vec structure
  19  * with page frame numbers or page pointers to corresponding pages (choice
  20  * depends on the type of the vma underlying the virtual address). If @start
  21  * belongs to a normal vma, the function grabs reference to each of the pages
  22  * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
  23  * touch page structures and the caller must make sure pfns aren't reused for
  24  * anything else while he is using them.
  25  *
  26  * The function returns number of pages mapped which may be less than
  27  * @nr_frames. In particular we stop mapping if there are more vmas of
  28  * different type underlying the specified range of virtual addresses.
  29  * When the function isn't able to map a single page, it returns error.
  30  *
  31  * This function takes care of grabbing mmap_sem as necessary.
  32  */
  33 int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
  34                      unsigned int gup_flags, struct frame_vector *vec)
  35 {
  36         struct mm_struct *mm = current->mm;
  37         struct vm_area_struct *vma;
  38         int ret = 0;
  39         int err;
  40         int locked;
  41
  42         if (nr_frames == 0)
  43                 return 0;
  44
  45         if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
  46                 nr_frames = vec->nr_allocated;
  47
  48         down_read(&mm->mmap_sem);
  49         locked = 1;
  50         vma = find_vma_intersection(mm, start, start + 1);
  51         if (!vma) {
  52                 ret = -EFAULT;
  53                 goto out;
  54         }
  55
  56         /*
  57          * While get_vaddr_frames() could be used for transient (kernel
  58          * controlled lifetime) pinning of memory pages all current
  59          * users establish long term (userspace controlled lifetime)
  60          * page pinning. Treat get_vaddr_frames() like
  61          * get_user_pages_longterm() and disallow it for filesystem-dax
  62          * mappings.
  63          */
  64         if (vma_is_fsdax(vma)) {
  65                 ret = -EOPNOTSUPP;
  66                 goto out;
  67         }
  68
  69         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
  70                 vec->got_ref = true;
  71                 vec->is_pfns = false;
  72                 ret = get_user_pages_locked(start, nr_frames,
  73                         gup_flags, (struct page **)(vec->ptrs), &locked);
  74                 goto out;
  75         }
  76
  77         vec->got_ref = false;
  78         vec->is_pfns = true;
  79         do {
  80                 unsigned long *nums = frame_vector_pfns(vec);
  81
  82                 while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
  83                         err = follow_pfn(vma, start, &nums[ret]);
  84                         if (err) {
  85                                 if (ret == 0)
  86                                         ret = err;
  87                                 goto out;
  88                         }
  89                         start += PAGE_SIZE;
  90                         ret++;
  91                 }
  92                 /*
  93                  * We stop if we have enough pages or if VMA doesn't completely
  94                  * cover the tail page.
  95                  */
  96                 if (ret >= nr_frames || start < vma->vm_end)
  97                         break;
  98                 vma = find_vma_intersection(mm, start, start + 1);
  99         } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
 100 out:
 101         if (locked)
 102                 up_read(&mm->mmap_sem);
 103         if (!ret)
 104                 ret = -EFAULT;
 105         if (ret > 0)
 106                 vec->nr_frames = ret;
 107         return ret;
 108 }
 109 EXPORT_SYMBOL(get_vaddr_frames);
 110
 111 /**
 112  * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
 113  *                      them
 114  * @vec:        frame vector to put
 115  *
 116  * Drop references to pages if get_vaddr_frames() acquired them. We also
 117  * invalidate the frame vector so that it is prepared for the next call into
 118  * get_vaddr_frames().
 119  */
 120 void put_vaddr_frames(struct frame_vector *vec)
 121 {
 122         int i;
 123         struct page **pages;
 124
 125         if (!vec->got_ref)
 126                 goto out;
 127         pages = frame_vector_pages(vec);
 128         /*
 129          * frame_vector_pages() might needed to do a conversion when
 130          * get_vaddr_frames() got pages but vec was later converted to pfns.
 131          * But it shouldn't really fail to convert pfns back...
 132          */
 133         if (WARN_ON(IS_ERR(pages)))
 134                 goto out;
 135         for (i = 0; i < vec->nr_frames; i++)
 136                 put_page(pages[i]);
 137         vec->got_ref = false;
 138 out:
 139         vec->nr_frames = 0;
 140 }
 141 EXPORT_SYMBOL(put_vaddr_frames);
 142
 143 /**
 144  * frame_vector_to_pages - convert frame vector to contain page pointers
 145  * @vec:        frame vector to convert
 146  *
 147  * Convert @vec to contain array of page pointers.  If the conversion is
 148  * successful, return 0. Otherwise return an error. Note that we do not grab
 149  * page references for the page structures.
 150  */
 151 int frame_vector_to_pages(struct frame_vector *vec)
 152 {
 153         int i;
 154         unsigned long *nums;
 155         struct page **pages;
 156
 157         if (!vec->is_pfns)
 158                 return 0;
 159         nums = frame_vector_pfns(vec);
 160         for (i = 0; i < vec->nr_frames; i++)
 161                 if (!pfn_valid(nums[i]))
 162                         return -EINVAL;
 163         pages = (struct page **)nums;
 164         for (i = 0; i < vec->nr_frames; i++)
 165                 pages[i] = pfn_to_page(nums[i]);
 166         vec->is_pfns = false;
 167         return 0;
 168 }
 169 EXPORT_SYMBOL(frame_vector_to_pages);
 170
 171 /**
 172  * frame_vector_to_pfns - convert frame vector to contain pfns
 173  * @vec:        frame vector to convert
 174  *
 175  * Convert @vec to contain array of pfns.
 176  */
 177 void frame_vector_to_pfns(struct frame_vector *vec)
 178 {
 179         int i;
 180         unsigned long *nums;
 181         struct page **pages;
 182
 183         if (vec->is_pfns)
 184                 return;
 185         pages = (struct page **)(vec->ptrs);
 186         nums = (unsigned long *)pages;
 187         for (i = 0; i < vec->nr_frames; i++)
 188                 nums[i] = page_to_pfn(pages[i]);
 189         vec->is_pfns = true;
 190 }
 191 EXPORT_SYMBOL(frame_vector_to_pfns);
 192
 193 /**
 194  * frame_vector_create() - allocate & initialize structure for pinned pfns
 195  * @nr_frames:  number of pfns slots we should reserve
 196  *
 197  * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
 198  * pfns.
 199  */
 200 struct frame_vector *frame_vector_create(unsigned int nr_frames)
 201 {
 202         struct frame_vector *vec;
 203         int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
 204
 205         if (WARN_ON_ONCE(nr_frames == 0))
 206                 return NULL;
 207         /*
 208          * This is absurdly high. It's here just to avoid strange effects when
 209          * arithmetics overflows.
 210          */
 211         if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
 212                 return NULL;
 213         /*
 214          * Avoid higher order allocations, use vmalloc instead. It should
 215          * be rare anyway.
 216          */
 217         if (size <= PAGE_SIZE)
 218                 vec = kmalloc(size, GFP_KERNEL);
 219         else
 220                 vec = vmalloc(size);
 221         if (!vec)
 222                 return NULL;
 223         vec->nr_allocated = nr_frames;
 224         vec->nr_frames = 0;
 225         return vec;
 226 }
 227 EXPORT_SYMBOL(frame_vector_create);
 228
 229 /**
 230  * frame_vector_destroy() - free memory allocated to carry frame vector
 231  * @vec:        Frame vector to free
 232  *
 233  * Free structure allocated by frame_vector_create() to carry frames.
 234  */
 235 void frame_vector_destroy(struct frame_vector *vec)
 236 {
 237         /* Make sure put_vaddr_frames() got called properly... */
 238         VM_BUG_ON(vec->nr_frames > 0);
 239         kvfree(vec);
 240 }
 241 EXPORT_SYMBOL(frame_vector_destroy);