lib/iov_iter.c

   1 #include <linux/export.h>
   2 #include <linux/bvec.h>
   3 #include <linux/uio.h>
   4 #include <linux/pagemap.h>
   5 #include <linux/slab.h>
   6 #include <linux/vmalloc.h>
   7 #include <linux/splice.h>
   8 #include <net/checksum.h>
   9
  10 #define PIPE_PARANOIA /* for now */
  11
  12 #define iterate_iovec(i, n, __v, __p, skip, STEP) {     \
  13         size_t left;                                    \
  14         size_t wanted = n;                              \
  15         __p = i->iov;                                   \
  16         __v.iov_len = min(n, __p->iov_len - skip);      \
  17         if (likely(__v.iov_len)) {                      \
  18                 __v.iov_base = __p->iov_base + skip;    \
  19                 left = (STEP);                          \
  20                 __v.iov_len -= left;                    \
  21                 skip += __v.iov_len;                    \
  22                 n -= __v.iov_len;                       \
  23         } else {                                        \
  24                 left = 0;                               \
  25         }                                               \
  26         while (unlikely(!left && n)) {                  \
  27                 __p++;                                  \
  28                 __v.iov_len = min(n, __p->iov_len);     \
  29                 if (unlikely(!__v.iov_len))             \
  30                         continue;                       \
  31                 __v.iov_base = __p->iov_base;           \
  32                 left = (STEP);                          \
  33                 __v.iov_len -= left;                    \
  34                 skip = __v.iov_len;                     \
  35                 n -= __v.iov_len;                       \
  36         }                                               \
  37         n = wanted - n;                                 \
  38 }
  39
  40 #define iterate_kvec(i, n, __v, __p, skip, STEP) {      \
  41         size_t wanted = n;                              \
  42         __p = i->kvec;                                  \
  43         __v.iov_len = min(n, __p->iov_len - skip);      \
  44         if (likely(__v.iov_len)) {                      \
  45                 __v.iov_base = __p->iov_base + skip;    \
  46                 (void)(STEP);                           \
  47                 skip += __v.iov_len;                    \
  48                 n -= __v.iov_len;                       \
  49         }                                               \
  50         while (unlikely(n)) {                           \
  51                 __p++;                                  \
  52                 __v.iov_len = min(n, __p->iov_len);     \
  53                 if (unlikely(!__v.iov_len))             \
  54                         continue;                       \
  55                 __v.iov_base = __p->iov_base;           \
  56                 (void)(STEP);                           \
  57                 skip = __v.iov_len;                     \
  58                 n -= __v.iov_len;                       \
  59         }                                               \
  60         n = wanted;                                     \
  61 }
  62
  63 #define iterate_bvec(i, n, __v, __bi, skip, STEP) {     \
  64         struct bvec_iter __start;                       \
  65         __start.bi_size = n;                            \
  66         __start.bi_bvec_done = skip;                    \
  67         __start.bi_idx = 0;                             \
  68         for_each_bvec(__v, i->bvec, __bi, __start) {    \
  69                 if (!__v.bv_len)                        \
  70                         continue;                       \
  71                 (void)(STEP);                           \
  72         }                                               \
  73 }
  74
  75 #define iterate_all_kinds(i, n, v, I, B, K) {                   \
  76         if (likely(n)) {                                        \
  77                 size_t skip = i->iov_offset;                    \
  78                 if (unlikely(i->type & ITER_BVEC)) {            \
  79                         struct bio_vec v;                       \
  80                         struct bvec_iter __bi;                  \
  81                         iterate_bvec(i, n, v, __bi, skip, (B))  \
  82                 } else if (unlikely(i->type & ITER_KVEC)) {     \
  83                         const struct kvec *kvec;                \
  84                         struct kvec v;                          \
  85                         iterate_kvec(i, n, v, kvec, skip, (K))  \
  86                 } else {                                        \
  87                         const struct iovec *iov;                \
  88                         struct iovec v;                         \
  89                         iterate_iovec(i, n, v, iov, skip, (I))  \
  90                 }                                               \
  91         }                                                       \
  92 }
  93
  94 #define iterate_and_advance(i, n, v, I, B, K) {                 \
  95         if (unlikely(i->count < n))                             \
  96                 n = i->count;                                   \
  97         if (i->count) {                                         \
  98                 size_t skip = i->iov_offset;                    \
  99                 if (unlikely(i->type & ITER_BVEC)) {            \
 100                         const struct bio_vec *bvec = i->bvec;   \
 101                         struct bio_vec v;                       \
 102                         struct bvec_iter __bi;                  \
 103                         iterate_bvec(i, n, v, __bi, skip, (B))  \
 104                         i->bvec = __bvec_iter_bvec(i->bvec, __bi);      \
 105                         i->nr_segs -= i->bvec - bvec;           \
 106                         skip = __bi.bi_bvec_done;               \
 107                 } else if (unlikely(i->type & ITER_KVEC)) {     \
 108                         const struct kvec *kvec;                \
 109                         struct kvec v;                          \
 110                         iterate_kvec(i, n, v, kvec, skip, (K))  \
 111                         if (skip == kvec->iov_len) {            \
 112                                 kvec++;                         \
 113                                 skip = 0;                       \
 114                         }                                       \
 115                         i->nr_segs -= kvec - i->kvec;           \
 116                         i->kvec = kvec;                         \
 117                 } else {                                        \
 118                         const struct iovec *iov;                \
 119                         struct iovec v;                         \
 120                         iterate_iovec(i, n, v, iov, skip, (I))  \
 121                         if (skip == iov->iov_len) {             \
 122                                 iov++;                          \
 123                                 skip = 0;                       \
 124                         }                                       \
 125                         i->nr_segs -= iov - i->iov;             \
 126                         i->iov = iov;                           \
 127                 }                                               \
 128                 i->count -= n;                                  \
 129                 i->iov_offset = skip;                           \
 130         }                                                       \
 131 }
 132
 133 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
 134                          struct iov_iter *i)
 135 {
 136         size_t skip, copy, left, wanted;
 137         const struct iovec *iov;
 138         char __user *buf;
 139         void *kaddr, *from;
 140
 141         if (unlikely(bytes > i->count))
 142                 bytes = i->count;
 143
 144         if (unlikely(!bytes))
 145                 return 0;
 146
 147         wanted = bytes;
 148         iov = i->iov;
 149         skip = i->iov_offset;
 150         buf = iov->iov_base + skip;
 151         copy = min(bytes, iov->iov_len - skip);
 152
 153         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
 154                 kaddr = kmap_atomic(page);
 155                 from = kaddr + offset;
 156
 157                 /* first chunk, usually the only one */
 158                 left = __copy_to_user_inatomic(buf, from, copy);
 159                 copy -= left;
 160                 skip += copy;
 161                 from += copy;
 162                 bytes -= copy;
 163
 164                 while (unlikely(!left && bytes)) {
 165                         iov++;
 166                         buf = iov->iov_base;
 167                         copy = min(bytes, iov->iov_len);
 168                         left = __copy_to_user_inatomic(buf, from, copy);
 169                         copy -= left;
 170                         skip = copy;
 171                         from += copy;
 172                         bytes -= copy;
 173                 }
 174                 if (likely(!bytes)) {
 175                         kunmap_atomic(kaddr);
 176                         goto done;
 177                 }
 178                 offset = from - kaddr;
 179                 buf += copy;
 180                 kunmap_atomic(kaddr);
 181                 copy = min(bytes, iov->iov_len - skip);
 182         }
 183         /* Too bad - revert to non-atomic kmap */
 184
 185         kaddr = kmap(page);
 186         from = kaddr + offset;
 187         left = __copy_to_user(buf, from, copy);
 188         copy -= left;
 189         skip += copy;
 190         from += copy;
 191         bytes -= copy;
 192         while (unlikely(!left && bytes)) {
 193                 iov++;
 194                 buf = iov->iov_base;
 195                 copy = min(bytes, iov->iov_len);
 196                 left = __copy_to_user(buf, from, copy);
 197                 copy -= left;
 198                 skip = copy;
 199                 from += copy;
 200                 bytes -= copy;
 201         }
 202         kunmap(page);
 203
 204 done:
 205         if (skip == iov->iov_len) {
 206                 iov++;
 207                 skip = 0;
 208         }
 209         i->count -= wanted - bytes;
 210         i->nr_segs -= iov - i->iov;
 211         i->iov = iov;
 212         i->iov_offset = skip;
 213         return wanted - bytes;
 214 }
 215
 216 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
 217                          struct iov_iter *i)
 218 {
 219         size_t skip, copy, left, wanted;
 220         const struct iovec *iov;
 221         char __user *buf;
 222         void *kaddr, *to;
 223
 224         if (unlikely(bytes > i->count))
 225                 bytes = i->count;
 226
 227         if (unlikely(!bytes))
 228                 return 0;
 229
 230         wanted = bytes;
 231         iov = i->iov;
 232         skip = i->iov_offset;
 233         buf = iov->iov_base + skip;
 234         copy = min(bytes, iov->iov_len - skip);
 235
 236         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
 237                 kaddr = kmap_atomic(page);
 238                 to = kaddr + offset;
 239
 240                 /* first chunk, usually the only one */
 241                 left = __copy_from_user_inatomic(to, buf, copy);
 242                 copy -= left;
 243                 skip += copy;
 244                 to += copy;
 245                 bytes -= copy;
 246
 247                 while (unlikely(!left && bytes)) {
 248                         iov++;
 249                         buf = iov->iov_base;
 250                         copy = min(bytes, iov->iov_len);
 251                         left = __copy_from_user_inatomic(to, buf, copy);
 252                         copy -= left;
 253                         skip = copy;
 254                         to += copy;
 255                         bytes -= copy;
 256                 }
 257                 if (likely(!bytes)) {
 258                         kunmap_atomic(kaddr);
 259                         goto done;
 260                 }
 261                 offset = to - kaddr;
 262                 buf += copy;
 263                 kunmap_atomic(kaddr);
 264                 copy = min(bytes, iov->iov_len - skip);
 265         }
 266         /* Too bad - revert to non-atomic kmap */
 267
 268         kaddr = kmap(page);
 269         to = kaddr + offset;
 270         left = __copy_from_user(to, buf, copy);
 271         copy -= left;
 272         skip += copy;
 273         to += copy;
 274         bytes -= copy;
 275         while (unlikely(!left && bytes)) {
 276                 iov++;
 277                 buf = iov->iov_base;
 278                 copy = min(bytes, iov->iov_len);
 279                 left = __copy_from_user(to, buf, copy);
 280                 copy -= left;
 281                 skip = copy;
 282                 to += copy;
 283                 bytes -= copy;
 284         }
 285         kunmap(page);
 286
 287 done:
 288         if (skip == iov->iov_len) {
 289                 iov++;
 290                 skip = 0;
 291         }
 292         i->count -= wanted - bytes;
 293         i->nr_segs -= iov - i->iov;
 294         i->iov = iov;
 295         i->iov_offset = skip;
 296         return wanted - bytes;
 297 }
 298
 299 #ifdef PIPE_PARANOIA
 300 static bool sanity(const struct iov_iter *i)
 301 {
 302         struct pipe_inode_info *pipe = i->pipe;
 303         int idx = i->idx;
 304         int next = pipe->curbuf + pipe->nrbufs;
 305         if (i->iov_offset) {
 306                 struct pipe_buffer *p;
 307                 if (unlikely(!pipe->nrbufs))
 308                         goto Bad;       // pipe must be non-empty
 309                 if (unlikely(idx != ((next - 1) & (pipe->buffers - 1))))
 310                         goto Bad;       // must be at the last buffer...
 311
 312                 p = &pipe->bufs[idx];
 313                 if (unlikely(p->offset + p->len != i->iov_offset))
 314                         goto Bad;       // ... at the end of segment
 315         } else {
 316                 if (idx != (next & (pipe->buffers - 1)))
 317                         goto Bad;       // must be right after the last buffer
 318         }
 319         return true;
 320 Bad:
 321         printk(KERN_ERR "idx = %d, offset = %zd\n", i->idx, i->iov_offset);
 322         printk(KERN_ERR "curbuf = %d, nrbufs = %d, buffers = %d\n",
 323                         pipe->curbuf, pipe->nrbufs, pipe->buffers);
 324         for (idx = 0; idx < pipe->buffers; idx++)
 325                 printk(KERN_ERR "[%p %p %d %d]\n",
 326                         pipe->bufs[idx].ops,
 327                         pipe->bufs[idx].page,
 328                         pipe->bufs[idx].offset,
 329                         pipe->bufs[idx].len);
 330         WARN_ON(1);
 331         return false;
 332 }
 333 #else
 334 #define sanity(i) true
 335 #endif
 336
 337 static inline int next_idx(int idx, struct pipe_inode_info *pipe)
 338 {
 339         return (idx + 1) & (pipe->buffers - 1);
 340 }
 341
 342 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
 343                          struct iov_iter *i)
 344 {
 345         struct pipe_inode_info *pipe = i->pipe;
 346         struct pipe_buffer *buf;
 347         size_t off;
 348         int idx;
 349
 350         if (unlikely(bytes > i->count))
 351                 bytes = i->count;
 352
 353         if (unlikely(!bytes))
 354                 return 0;
 355
 356         if (!sanity(i))
 357                 return 0;
 358
 359         off = i->iov_offset;
 360         idx = i->idx;
 361         buf = &pipe->bufs[idx];
 362         if (off) {
 363                 if (offset == off && buf->page == page) {
 364                         /* merge with the last one */
 365                         buf->len += bytes;
 366                         i->iov_offset += bytes;
 367                         goto out;
 368                 }
 369                 idx = next_idx(idx, pipe);
 370                 buf = &pipe->bufs[idx];
 371         }
 372         if (idx == pipe->curbuf && pipe->nrbufs)
 373                 return 0;
 374         pipe->nrbufs++;
 375         buf->ops = &page_cache_pipe_buf_ops;
 376         get_page(buf->page = page);
 377         buf->offset = offset;
 378         buf->len = bytes;
 379         i->iov_offset = offset + bytes;
 380         i->idx = idx;
 381 out:
 382         i->count -= bytes;
 383         return bytes;
 384 }
 385
 386 /*
 387  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 388  * bytes.  For each iovec, fault in each page that constitutes the iovec.
 389  *
 390  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 391  * because it is an invalid address).
 392  */
 393 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 394 {
 395         size_t skip = i->iov_offset;
 396         const struct iovec *iov;
 397         int err;
 398         struct iovec v;
 399
 400         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 401                 iterate_iovec(i, bytes, v, iov, skip, ({
 402                         err = fault_in_pages_readable(v.iov_base, v.iov_len);
 403                         if (unlikely(err))
 404                         return err;
 405                 0;}))
 406         }
 407         return 0;
 408 }
 409 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 410
 411 void iov_iter_init(struct iov_iter *i, int direction,
 412                         const struct iovec *iov, unsigned long nr_segs,
 413                         size_t count)
 414 {
 415         /* It will get better.  Eventually... */
 416         if (uaccess_kernel()) {
 417                 direction |= ITER_KVEC;
 418                 i->type = direction;
 419                 i->kvec = (struct kvec *)iov;
 420         } else {
 421                 i->type = direction;
 422                 i->iov = iov;
 423         }
 424         i->nr_segs = nr_segs;
 425         i->iov_offset = 0;
 426         i->count = count;
 427 }
 428 EXPORT_SYMBOL(iov_iter_init);
 429
 430 static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
 431 {
 432         char *from = kmap_atomic(page);
 433         memcpy(to, from + offset, len);
 434         kunmap_atomic(from);
 435 }
 436
 437 static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 438 {
 439         char *to = kmap_atomic(page);
 440         memcpy(to + offset, from, len);
 441         kunmap_atomic(to);
 442 }
 443
 444 static void memzero_page(struct page *page, size_t offset, size_t len)
 445 {
 446         char *addr = kmap_atomic(page);
 447         memset(addr + offset, 0, len);
 448         kunmap_atomic(addr);
 449 }
 450
 451 static inline bool allocated(struct pipe_buffer *buf)
 452 {
 453         return buf->ops == &default_pipe_buf_ops;
 454 }
 455
 456 static inline void data_start(const struct iov_iter *i, int *idxp, size_t *offp)
 457 {
 458         size_t off = i->iov_offset;
 459         int idx = i->idx;
 460         if (off && (!allocated(&i->pipe->bufs[idx]) || off == PAGE_SIZE)) {
 461                 idx = next_idx(idx, i->pipe);
 462                 off = 0;
 463         }
 464         *idxp = idx;
 465         *offp = off;
 466 }
 467
 468 static size_t push_pipe(struct iov_iter *i, size_t size,
 469                         int *idxp, size_t *offp)
 470 {
 471         struct pipe_inode_info *pipe = i->pipe;
 472         size_t off;
 473         int idx;
 474         ssize_t left;
 475
 476         if (unlikely(size > i->count))
 477                 size = i->count;
 478         if (unlikely(!size))
 479                 return 0;
 480
 481         left = size;
 482         data_start(i, &idx, &off);
 483         *idxp = idx;
 484         *offp = off;
 485         if (off) {
 486                 left -= PAGE_SIZE - off;
 487                 if (left <= 0) {
 488                         pipe->bufs[idx].len += size;
 489                         return size;
 490                 }
 491                 pipe->bufs[idx].len = PAGE_SIZE;
 492                 idx = next_idx(idx, pipe);
 493         }
 494         while (idx != pipe->curbuf || !pipe->nrbufs) {
 495                 struct page *page = alloc_page(GFP_USER);
 496                 if (!page)
 497                         break;
 498                 pipe->nrbufs++;
 499                 pipe->bufs[idx].ops = &default_pipe_buf_ops;
 500                 pipe->bufs[idx].page = page;
 501                 pipe->bufs[idx].offset = 0;
 502                 if (left <= PAGE_SIZE) {
 503                         pipe->bufs[idx].len = left;
 504                         return size;
 505                 }
 506                 pipe->bufs[idx].len = PAGE_SIZE;
 507                 left -= PAGE_SIZE;
 508                 idx = next_idx(idx, pipe);
 509         }
 510         return size - left;
 511 }
 512
 513 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
 514                                 struct iov_iter *i)
 515 {
 516         struct pipe_inode_info *pipe = i->pipe;
 517         size_t n, off;
 518         int idx;
 519
 520         if (!sanity(i))
 521                 return 0;
 522
 523         bytes = n = push_pipe(i, bytes, &idx, &off);
 524         if (unlikely(!n))
 525                 return 0;
 526         for ( ; n; idx = next_idx(idx, pipe), off = 0) {
 527                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 528                 memcpy_to_page(pipe->bufs[idx].page, off, addr, chunk);
 529                 i->idx = idx;
 530                 i->iov_offset = off + chunk;
 531                 n -= chunk;
 532                 addr += chunk;
 533         }
 534         i->count -= bytes;
 535         return bytes;
 536 }
 537
 538 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 539 {
 540         const char *from = addr;
 541         if (unlikely(i->type & ITER_PIPE))
 542                 return copy_pipe_to_iter(addr, bytes, i);
 543         iterate_and_advance(i, bytes, v,
 544                 __copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
 545                                v.iov_len),
 546                 memcpy_to_page(v.bv_page, v.bv_offset,
 547                                (from += v.bv_len) - v.bv_len, v.bv_len),
 548                 memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
 549         )
 550
 551         return bytes;
 552 }
 553 EXPORT_SYMBOL(copy_to_iter);
 554
 555 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 556 {
 557         char *to = addr;
 558         if (unlikely(i->type & ITER_PIPE)) {
 559                 WARN_ON(1);
 560                 return 0;
 561         }
 562         iterate_and_advance(i, bytes, v,
 563                 __copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
 564                                  v.iov_len),
 565                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 566                                  v.bv_offset, v.bv_len),
 567                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 568         )
 569
 570         return bytes;
 571 }
 572 EXPORT_SYMBOL(copy_from_iter);
 573
 574 bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 575 {
 576         char *to = addr;
 577         if (unlikely(i->type & ITER_PIPE)) {
 578                 WARN_ON(1);
 579                 return false;
 580         }
 581         if (unlikely(i->count < bytes))
 582                 return false;
 583
 584         iterate_all_kinds(i, bytes, v, ({
 585                 if (__copy_from_user((to += v.iov_len) - v.iov_len,
 586                                       v.iov_base, v.iov_len))
 587                         return false;
 588                 0;}),
 589                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 590                                  v.bv_offset, v.bv_len),
 591                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 592         )
 593
 594         iov_iter_advance(i, bytes);
 595         return true;
 596 }
 597 EXPORT_SYMBOL(copy_from_iter_full);
 598
 599 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 600 {
 601         char *to = addr;
 602         if (unlikely(i->type & ITER_PIPE)) {
 603                 WARN_ON(1);
 604                 return 0;
 605         }
 606         iterate_and_advance(i, bytes, v,
 607                 __copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 608                                          v.iov_base, v.iov_len),
 609                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 610                                  v.bv_offset, v.bv_len),
 611                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 612         )
 613
 614         return bytes;
 615 }
 616 EXPORT_SYMBOL(copy_from_iter_nocache);
 617
 618 bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 619 {
 620         char *to = addr;
 621         if (unlikely(i->type & ITER_PIPE)) {
 622                 WARN_ON(1);
 623                 return false;
 624         }
 625         if (unlikely(i->count < bytes))
 626                 return false;
 627         iterate_all_kinds(i, bytes, v, ({
 628                 if (__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 629                                              v.iov_base, v.iov_len))
 630                         return false;
 631                 0;}),
 632                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 633                                  v.bv_offset, v.bv_len),
 634                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 635         )
 636
 637         iov_iter_advance(i, bytes);
 638         return true;
 639 }
 640 EXPORT_SYMBOL(copy_from_iter_full_nocache);
 641
 642 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 643                          struct iov_iter *i)
 644 {
 645         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 646                 void *kaddr = kmap_atomic(page);
 647                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 648                 kunmap_atomic(kaddr);
 649                 return wanted;
 650         } else if (likely(!(i->type & ITER_PIPE)))
 651                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 652         else
 653                 return copy_page_to_iter_pipe(page, offset, bytes, i);
 654 }
 655 EXPORT_SYMBOL(copy_page_to_iter);
 656
 657 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 658                          struct iov_iter *i)
 659 {
 660         if (unlikely(i->type & ITER_PIPE)) {
 661                 WARN_ON(1);
 662                 return 0;
 663         }
 664         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 665                 void *kaddr = kmap_atomic(page);
 666                 size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
 667                 kunmap_atomic(kaddr);
 668                 return wanted;
 669         } else
 670                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 671 }
 672 EXPORT_SYMBOL(copy_page_from_iter);
 673
 674 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
 675 {
 676         struct pipe_inode_info *pipe = i->pipe;
 677         size_t n, off;
 678         int idx;
 679
 680         if (!sanity(i))
 681                 return 0;
 682
 683         bytes = n = push_pipe(i, bytes, &idx, &off);
 684         if (unlikely(!n))
 685                 return 0;
 686
 687         for ( ; n; idx = next_idx(idx, pipe), off = 0) {
 688                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 689                 memzero_page(pipe->bufs[idx].page, off, chunk);
 690                 i->idx = idx;
 691                 i->iov_offset = off + chunk;
 692                 n -= chunk;
 693         }
 694         i->count -= bytes;
 695         return bytes;
 696 }
 697
 698 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 699 {
 700         if (unlikely(i->type & ITER_PIPE))
 701                 return pipe_zero(bytes, i);
 702         iterate_and_advance(i, bytes, v,
 703                 __clear_user(v.iov_base, v.iov_len),
 704                 memzero_page(v.bv_page, v.bv_offset, v.bv_len),
 705                 memset(v.iov_base, 0, v.iov_len)
 706         )
 707
 708         return bytes;
 709 }
 710 EXPORT_SYMBOL(iov_iter_zero);
 711
 712 size_t iov_iter_copy_from_user_atomic(struct page *page,
 713                 struct iov_iter *i, unsigned long offset, size_t bytes)
 714 {
 715         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 716         if (unlikely(i->type & ITER_PIPE)) {
 717                 kunmap_atomic(kaddr);
 718                 WARN_ON(1);
 719                 return 0;
 720         }
 721         iterate_all_kinds(i, bytes, v,
 722                 __copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
 723                                           v.iov_base, v.iov_len),
 724                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 725                                  v.bv_offset, v.bv_len),
 726                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 727         )
 728         kunmap_atomic(kaddr);
 729         return bytes;
 730 }
 731 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 732
 733 static inline void pipe_truncate(struct iov_iter *i)
 734 {
 735         struct pipe_inode_info *pipe = i->pipe;
 736         if (pipe->nrbufs) {
 737                 size_t off = i->iov_offset;
 738                 int idx = i->idx;
 739                 int nrbufs = (idx - pipe->curbuf) & (pipe->buffers - 1);
 740                 if (off) {
 741                         pipe->bufs[idx].len = off - pipe->bufs[idx].offset;
 742                         idx = next_idx(idx, pipe);
 743                         nrbufs++;
 744                 }
 745                 while (pipe->nrbufs > nrbufs) {
 746                         pipe_buf_release(pipe, &pipe->bufs[idx]);
 747                         idx = next_idx(idx, pipe);
 748                         pipe->nrbufs--;
 749                 }
 750         }
 751 }
 752
 753 static void pipe_advance(struct iov_iter *i, size_t size)
 754 {
 755         struct pipe_inode_info *pipe = i->pipe;
 756         if (unlikely(i->count < size))
 757                 size = i->count;
 758         if (size) {
 759                 struct pipe_buffer *buf;
 760                 size_t off = i->iov_offset, left = size;
 761                 int idx = i->idx;
 762                 if (off) /* make it relative to the beginning of buffer */
 763                         left += off - pipe->bufs[idx].offset;
 764                 while (1) {
 765                         buf = &pipe->bufs[idx];
 766                         if (left <= buf->len)
 767                                 break;
 768                         left -= buf->len;
 769                         idx = next_idx(idx, pipe);
 770                 }
 771                 i->idx = idx;
 772                 i->iov_offset = buf->offset + left;
 773         }
 774         i->count -= size;
 775         /* ... and discard everything past that point */
 776         pipe_truncate(i);
 777 }
 778
 779 void iov_iter_advance(struct iov_iter *i, size_t size)
 780 {
 781         if (unlikely(i->type & ITER_PIPE)) {
 782                 pipe_advance(i, size);
 783                 return;
 784         }
 785         iterate_and_advance(i, size, v, 0, 0, 0)
 786 }
 787 EXPORT_SYMBOL(iov_iter_advance);
 788
 789 void iov_iter_revert(struct iov_iter *i, size_t unroll)
 790 {
 791         if (!unroll)
 792                 return;
 793         if (WARN_ON(unroll > MAX_RW_COUNT))
 794                 return;
 795         i->count += unroll;
 796         if (unlikely(i->type & ITER_PIPE)) {
 797                 struct pipe_inode_info *pipe = i->pipe;
 798                 int idx = i->idx;
 799                 size_t off = i->iov_offset;
 800                 while (1) {
 801                         size_t n = off - pipe->bufs[idx].offset;
 802                         if (unroll < n) {
 803                                 off -= unroll;
 804                                 break;
 805                         }
 806                         unroll -= n;
 807                         if (!unroll && idx == i->start_idx) {
 808                                 off = 0;
 809                                 break;
 810                         }
 811                         if (!idx--)
 812                                 idx = pipe->buffers - 1;
 813                         off = pipe->bufs[idx].offset + pipe->bufs[idx].len;
 814                 }
 815                 i->iov_offset = off;
 816                 i->idx = idx;
 817                 pipe_truncate(i);
 818                 return;
 819         }
 820         if (unroll <= i->iov_offset) {
 821                 i->iov_offset -= unroll;
 822                 return;
 823         }
 824         unroll -= i->iov_offset;
 825         if (i->type & ITER_BVEC) {
 826                 const struct bio_vec *bvec = i->bvec;
 827                 while (1) {
 828                         size_t n = (--bvec)->bv_len;
 829                         i->nr_segs++;
 830                         if (unroll <= n) {
 831                                 i->bvec = bvec;
 832                                 i->iov_offset = n - unroll;
 833                                 return;
 834                         }
 835                         unroll -= n;
 836                 }
 837         } else { /* same logics for iovec and kvec */
 838                 const struct iovec *iov = i->iov;
 839                 while (1) {
 840                         size_t n = (--iov)->iov_len;
 841                         i->nr_segs++;
 842                         if (unroll <= n) {
 843                                 i->iov = iov;
 844                                 i->iov_offset = n - unroll;
 845                                 return;
 846                         }
 847                         unroll -= n;
 848                 }
 849         }
 850 }
 851 EXPORT_SYMBOL(iov_iter_revert);
 852
 853 /*
 854  * Return the count of just the current iov_iter segment.
 855  */
 856 size_t iov_iter_single_seg_count(const struct iov_iter *i)
 857 {
 858         if (unlikely(i->type & ITER_PIPE))
 859                 return i->count;        // it is a silly place, anyway
 860         if (i->nr_segs == 1)
 861                 return i->count;
 862         else if (i->type & ITER_BVEC)
 863                 return min(i->count, i->bvec->bv_len - i->iov_offset);
 864         else
 865                 return min(i->count, i->iov->iov_len - i->iov_offset);
 866 }
 867 EXPORT_SYMBOL(iov_iter_single_seg_count);
 868
 869 void iov_iter_kvec(struct iov_iter *i, int direction,
 870                         const struct kvec *kvec, unsigned long nr_segs,
 871                         size_t count)
 872 {
 873         BUG_ON(!(direction & ITER_KVEC));
 874         i->type = direction;
 875         i->kvec = kvec;
 876         i->nr_segs = nr_segs;
 877         i->iov_offset = 0;
 878         i->count = count;
 879 }
 880 EXPORT_SYMBOL(iov_iter_kvec);
 881
 882 void iov_iter_bvec(struct iov_iter *i, int direction,
 883                         const struct bio_vec *bvec, unsigned long nr_segs,
 884                         size_t count)
 885 {
 886         BUG_ON(!(direction & ITER_BVEC));
 887         i->type = direction;
 888         i->bvec = bvec;
 889         i->nr_segs = nr_segs;
 890         i->iov_offset = 0;
 891         i->count = count;
 892 }
 893 EXPORT_SYMBOL(iov_iter_bvec);
 894
 895 void iov_iter_pipe(struct iov_iter *i, int direction,
 896                         struct pipe_inode_info *pipe,
 897                         size_t count)
 898 {
 899         BUG_ON(direction != ITER_PIPE);
 900         WARN_ON(pipe->nrbufs == pipe->buffers);
 901         i->type = direction;
 902         i->pipe = pipe;
 903         i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 904         i->iov_offset = 0;
 905         i->count = count;
 906         i->start_idx = i->idx;
 907 }
 908 EXPORT_SYMBOL(iov_iter_pipe);
 909
 910 unsigned long iov_iter_alignment(const struct iov_iter *i)
 911 {
 912         unsigned long res = 0;
 913         size_t size = i->count;
 914
 915         if (unlikely(i->type & ITER_PIPE)) {
 916                 if (size && i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
 917                         return size | i->iov_offset;
 918                 return size;
 919         }
 920         iterate_all_kinds(i, size, v,
 921                 (res |= (unsigned long)v.iov_base | v.iov_len, 0),
 922                 res |= v.bv_offset | v.bv_len,
 923                 res |= (unsigned long)v.iov_base | v.iov_len
 924         )
 925         return res;
 926 }
 927 EXPORT_SYMBOL(iov_iter_alignment);
 928
 929 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 930 {
 931         unsigned long res = 0;
 932         size_t size = i->count;
 933
 934         if (unlikely(i->type & ITER_PIPE)) {
 935                 WARN_ON(1);
 936                 return ~0U;
 937         }
 938
 939         iterate_all_kinds(i, size, v,
 940                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
 941                         (size != v.iov_len ? size : 0), 0),
 942                 (res |= (!res ? 0 : (unsigned long)v.bv_offset) |
 943                         (size != v.bv_len ? size : 0)),
 944                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
 945                         (size != v.iov_len ? size : 0))
 946                 );
 947         return res;
 948 }
 949 EXPORT_SYMBOL(iov_iter_gap_alignment);
 950
 951 static inline size_t __pipe_get_pages(struct iov_iter *i,
 952                                 size_t maxsize,
 953                                 struct page **pages,
 954                                 int idx,
 955                                 size_t *start)
 956 {
 957         struct pipe_inode_info *pipe = i->pipe;
 958         ssize_t n = push_pipe(i, maxsize, &idx, start);
 959         if (!n)
 960                 return -EFAULT;
 961
 962         maxsize = n;
 963         n += *start;
 964         while (n > 0) {
 965                 get_page(*pages++ = pipe->bufs[idx].page);
 966                 idx = next_idx(idx, pipe);
 967                 n -= PAGE_SIZE;
 968         }
 969
 970         return maxsize;
 971 }
 972
 973 static ssize_t pipe_get_pages(struct iov_iter *i,
 974                    struct page **pages, size_t maxsize, unsigned maxpages,
 975                    size_t *start)
 976 {
 977         unsigned npages;
 978         size_t capacity;
 979         int idx;
 980
 981         if (!maxsize)
 982                 return 0;
 983
 984         if (!sanity(i))
 985                 return -EFAULT;
 986
 987         data_start(i, &idx, start);
 988         /* some of this one + all after this one */
 989         npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
 990         capacity = min(npages,maxpages) * PAGE_SIZE - *start;
 991
 992         return __pipe_get_pages(i, min(maxsize, capacity), pages, idx, start);
 993 }
 994
 995 ssize_t iov_iter_get_pages(struct iov_iter *i,
 996                    struct page **pages, size_t maxsize, unsigned maxpages,
 997                    size_t *start)
 998 {
 999         if (maxsize > i->count)
1000                 maxsize = i->count;
1001
1002         if (unlikely(i->type & ITER_PIPE))
1003                 return pipe_get_pages(i, pages, maxsize, maxpages, start);
1004         iterate_all_kinds(i, maxsize, v, ({
1005                 unsigned long addr = (unsigned long)v.iov_base;
1006                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1007                 int n;
1008                 int res;
1009
1010                 if (len > maxpages * PAGE_SIZE)
1011                         len = maxpages * PAGE_SIZE;
1012                 addr &= ~(PAGE_SIZE - 1);
1013                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1014                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
1015                 if (unlikely(res < 0))
1016                         return res;
1017                 return (res == n ? len : res * PAGE_SIZE) - *start;
1018         0;}),({
1019                 /* can't be more than PAGE_SIZE */
1020                 *start = v.bv_offset;
1021                 get_page(*pages = v.bv_page);
1022                 return v.bv_len;
1023         }),({
1024                 return -EFAULT;
1025         })
1026         )
1027         return 0;
1028 }
1029 EXPORT_SYMBOL(iov_iter_get_pages);
1030
1031 static struct page **get_pages_array(size_t n)
1032 {
1033         return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
1034 }
1035
1036 static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
1037                    struct page ***pages, size_t maxsize,
1038                    size_t *start)
1039 {
1040         struct page **p;
1041         size_t n;
1042         int idx;
1043         int npages;
1044
1045         if (!maxsize)
1046                 return 0;
1047
1048         if (!sanity(i))
1049                 return -EFAULT;
1050
1051         data_start(i, &idx, start);
1052         /* some of this one + all after this one */
1053         npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
1054         n = npages * PAGE_SIZE - *start;
1055         if (maxsize > n)
1056                 maxsize = n;
1057         else
1058                 npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
1059         p = get_pages_array(npages);
1060         if (!p)
1061                 return -ENOMEM;
1062         n = __pipe_get_pages(i, maxsize, p, idx, start);
1063         if (n > 0)
1064                 *pages = p;
1065         else
1066                 kvfree(p);
1067         return n;
1068 }
1069
1070 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
1071                    struct page ***pages, size_t maxsize,
1072                    size_t *start)
1073 {
1074         struct page **p;
1075
1076         if (maxsize > i->count)
1077                 maxsize = i->count;
1078
1079         if (unlikely(i->type & ITER_PIPE))
1080                 return pipe_get_pages_alloc(i, pages, maxsize, start);
1081         iterate_all_kinds(i, maxsize, v, ({
1082                 unsigned long addr = (unsigned long)v.iov_base;
1083                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1084                 int n;
1085                 int res;
1086
1087                 addr &= ~(PAGE_SIZE - 1);
1088                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1089                 p = get_pages_array(n);
1090                 if (!p)
1091                         return -ENOMEM;
1092                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
1093                 if (unlikely(res < 0)) {
1094                         kvfree(p);
1095                         return res;
1096                 }
1097                 *pages = p;
1098                 return (res == n ? len : res * PAGE_SIZE) - *start;
1099         0;}),({
1100                 /* can't be more than PAGE_SIZE */
1101                 *start = v.bv_offset;
1102                 *pages = p = get_pages_array(1);
1103                 if (!p)
1104                         return -ENOMEM;
1105                 get_page(*p = v.bv_page);
1106                 return v.bv_len;
1107         }),({
1108                 return -EFAULT;
1109         })
1110         )
1111         return 0;
1112 }
1113 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
1114
1115 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1116                                struct iov_iter *i)
1117 {
1118         char *to = addr;
1119         __wsum sum, next;
1120         size_t off = 0;
1121         sum = *csum;
1122         if (unlikely(i->type & ITER_PIPE)) {
1123                 WARN_ON(1);
1124                 return 0;
1125         }
1126         iterate_and_advance(i, bytes, v, ({
1127                 int err = 0;
1128                 next = csum_and_copy_from_user(v.iov_base,
1129                                                (to += v.iov_len) - v.iov_len,
1130                                                v.iov_len, 0, &err);
1131                 if (!err) {
1132                         sum = csum_block_add(sum, next, off);
1133                         off += v.iov_len;
1134                 }
1135                 err ? v.iov_len : 0;
1136         }), ({
1137                 char *p = kmap_atomic(v.bv_page);
1138                 next = csum_partial_copy_nocheck(p + v.bv_offset,
1139                                                  (to += v.bv_len) - v.bv_len,
1140                                                  v.bv_len, 0);
1141                 kunmap_atomic(p);
1142                 sum = csum_block_add(sum, next, off);
1143                 off += v.bv_len;
1144         }),({
1145                 next = csum_partial_copy_nocheck(v.iov_base,
1146                                                  (to += v.iov_len) - v.iov_len,
1147                                                  v.iov_len, 0);
1148                 sum = csum_block_add(sum, next, off);
1149                 off += v.iov_len;
1150         })
1151         )
1152         *csum = sum;
1153         return bytes;
1154 }
1155 EXPORT_SYMBOL(csum_and_copy_from_iter);
1156
1157 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
1158                                struct iov_iter *i)
1159 {
1160         char *to = addr;
1161         __wsum sum, next;
1162         size_t off = 0;
1163         sum = *csum;
1164         if (unlikely(i->type & ITER_PIPE)) {
1165                 WARN_ON(1);
1166                 return false;
1167         }
1168         if (unlikely(i->count < bytes))
1169                 return false;
1170         iterate_all_kinds(i, bytes, v, ({
1171                 int err = 0;
1172                 next = csum_and_copy_from_user(v.iov_base,
1173                                                (to += v.iov_len) - v.iov_len,
1174                                                v.iov_len, 0, &err);
1175                 if (err)
1176                         return false;
1177                 sum = csum_block_add(sum, next, off);
1178                 off += v.iov_len;
1179                 0;
1180         }), ({
1181                 char *p = kmap_atomic(v.bv_page);
1182                 next = csum_partial_copy_nocheck(p + v.bv_offset,
1183                                                  (to += v.bv_len) - v.bv_len,
1184                                                  v.bv_len, 0);
1185                 kunmap_atomic(p);
1186                 sum = csum_block_add(sum, next, off);
1187                 off += v.bv_len;
1188         }),({
1189                 next = csum_partial_copy_nocheck(v.iov_base,
1190                                                  (to += v.iov_len) - v.iov_len,
1191                                                  v.iov_len, 0);
1192                 sum = csum_block_add(sum, next, off);
1193                 off += v.iov_len;
1194         })
1195         )
1196         *csum = sum;
1197         iov_iter_advance(i, bytes);
1198         return true;
1199 }
1200 EXPORT_SYMBOL(csum_and_copy_from_iter_full);
1201
1202 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
1203                              struct iov_iter *i)
1204 {
1205         const char *from = addr;
1206         __wsum sum, next;
1207         size_t off = 0;
1208         sum = *csum;
1209         if (unlikely(i->type & ITER_PIPE)) {
1210                 WARN_ON(1);     /* for now */
1211                 return 0;
1212         }
1213         iterate_and_advance(i, bytes, v, ({
1214                 int err = 0;
1215                 next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
1216                                              v.iov_base,
1217                                              v.iov_len, 0, &err);
1218                 if (!err) {
1219                         sum = csum_block_add(sum, next, off);
1220                         off += v.iov_len;
1221                 }
1222                 err ? v.iov_len : 0;
1223         }), ({
1224                 char *p = kmap_atomic(v.bv_page);
1225                 next = csum_partial_copy_nocheck((from += v.bv_len) - v.bv_len,
1226                                                  p + v.bv_offset,
1227                                                  v.bv_len, 0);
1228                 kunmap_atomic(p);
1229                 sum = csum_block_add(sum, next, off);
1230                 off += v.bv_len;
1231         }),({
1232                 next = csum_partial_copy_nocheck((from += v.iov_len) - v.iov_len,
1233                                                  v.iov_base,
1234                                                  v.iov_len, 0);
1235                 sum = csum_block_add(sum, next, off);
1236                 off += v.iov_len;
1237         })
1238         )
1239         *csum = sum;
1240         return bytes;
1241 }
1242 EXPORT_SYMBOL(csum_and_copy_to_iter);
1243
1244 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1245 {
1246         size_t size = i->count;
1247         int npages = 0;
1248
1249         if (!size)
1250                 return 0;
1251
1252         if (unlikely(i->type & ITER_PIPE)) {
1253                 struct pipe_inode_info *pipe = i->pipe;
1254                 size_t off;
1255                 int idx;
1256
1257                 if (!sanity(i))
1258                         return 0;
1259
1260                 data_start(i, &idx, &off);
1261                 /* some of this one + all after this one */
1262                 npages = ((pipe->curbuf - idx - 1) & (pipe->buffers - 1)) + 1;
1263                 if (npages >= maxpages)
1264                         return maxpages;
1265         } else iterate_all_kinds(i, size, v, ({
1266                 unsigned long p = (unsigned long)v.iov_base;
1267                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1268                         - p / PAGE_SIZE;
1269                 if (npages >= maxpages)
1270                         return maxpages;
1271         0;}),({
1272                 npages++;
1273                 if (npages >= maxpages)
1274                         return maxpages;
1275         }),({
1276                 unsigned long p = (unsigned long)v.iov_base;
1277                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1278                         - p / PAGE_SIZE;
1279                 if (npages >= maxpages)
1280                         return maxpages;
1281         })
1282         )
1283         return npages;
1284 }
1285 EXPORT_SYMBOL(iov_iter_npages);
1286
1287 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1288 {
1289         *new = *old;
1290         if (unlikely(new->type & ITER_PIPE)) {
1291                 WARN_ON(1);
1292                 return NULL;
1293         }
1294         if (new->type & ITER_BVEC)
1295                 return new->bvec = kmemdup(new->bvec,
1296                                     new->nr_segs * sizeof(struct bio_vec),
1297                                     flags);
1298         else
1299                 /* iovec and kvec have identical layout */
1300                 return new->iov = kmemdup(new->iov,
1301                                    new->nr_segs * sizeof(struct iovec),
1302                                    flags);
1303 }
1304 EXPORT_SYMBOL(dup_iter);
1305
1306 /**
1307  * import_iovec() - Copy an array of &struct iovec from userspace
1308  *     into the kernel, check that it is valid, and initialize a new
1309  *     &struct iov_iter iterator to access it.
1310  *
1311  * @type: One of %READ or %WRITE.
1312  * @uvector: Pointer to the userspace array.
1313  * @nr_segs: Number of elements in userspace array.
1314  * @fast_segs: Number of elements in @iov.
1315  * @iov: (input and output parameter) Pointer to pointer to (usually small
1316  *     on-stack) kernel array.
1317  * @i: Pointer to iterator that will be initialized on success.
1318  *
1319  * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1320  * then this function places %NULL in *@iov on return. Otherwise, a new
1321  * array will be allocated and the result placed in *@iov. This means that
1322  * the caller may call kfree() on *@iov regardless of whether the small
1323  * on-stack array was used or not (and regardless of whether this function
1324  * returns an error or not).
1325  *
1326  * Return: 0 on success or negative error code on error.
1327  */
1328 int import_iovec(int type, const struct iovec __user * uvector,
1329                  unsigned nr_segs, unsigned fast_segs,
1330                  struct iovec **iov, struct iov_iter *i)
1331 {
1332         ssize_t n;
1333         struct iovec *p;
1334         n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1335                                   *iov, &p);
1336         if (n < 0) {
1337                 if (p != *iov)
1338                         kfree(p);
1339                 *iov = NULL;
1340                 return n;
1341         }
1342         iov_iter_init(i, type, p, nr_segs, n);
1343         *iov = p == *iov ? NULL : p;
1344         return 0;
1345 }
1346 EXPORT_SYMBOL(import_iovec);
1347
1348 #ifdef CONFIG_COMPAT
1349 #include <linux/compat.h>
1350
1351 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
1352                  unsigned nr_segs, unsigned fast_segs,
1353                  struct iovec **iov, struct iov_iter *i)
1354 {
1355         ssize_t n;
1356         struct iovec *p;
1357         n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1358                                   *iov, &p);
1359         if (n < 0) {
1360                 if (p != *iov)
1361                         kfree(p);
1362                 *iov = NULL;
1363                 return n;
1364         }
1365         iov_iter_init(i, type, p, nr_segs, n);
1366         *iov = p == *iov ? NULL : p;
1367         return 0;
1368 }
1369 #endif
1370
1371 int import_single_range(int rw, void __user *buf, size_t len,
1372                  struct iovec *iov, struct iov_iter *i)
1373 {
1374         if (len > MAX_RW_COUNT)
1375                 len = MAX_RW_COUNT;
1376         if (unlikely(!access_ok(!rw, buf, len)))
1377                 return -EFAULT;
1378
1379         iov->iov_base = buf;
1380         iov->iov_len = len;
1381         iov_iter_init(i, rw, iov, 1, len);
1382         return 0;
1383 }
1384 EXPORT_SYMBOL(import_single_range);