git.rot13.org Git - linux/blob - 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 int copyout(void __user *to, const void *from, size_t n)
 134 {
 135         if (access_ok(VERIFY_WRITE, to, n)) {
 136                 kasan_check_read(from, n);
 137                 n = raw_copy_to_user(to, from, n);
 138         }
 139         return n;
 140 }
 141
 142 static int copyin(void *to, const void __user *from, size_t n)
 143 {
 144         if (access_ok(VERIFY_READ, from, n)) {
 145                 kasan_check_write(to, n);
 146                 n = raw_copy_from_user(to, from, n);
 147         }
 148         return n;
 149 }
 150
 151 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
 152                          struct iov_iter *i)
 153 {
 154         size_t skip, copy, left, wanted;
 155         const struct iovec *iov;
 156         char __user *buf;
 157         void *kaddr, *from;
 158
 159         if (unlikely(bytes > i->count))
 160                 bytes = i->count;
 161
 162         if (unlikely(!bytes))
 163                 return 0;
 164
 165         might_fault();
 166         wanted = bytes;
 167         iov = i->iov;
 168         skip = i->iov_offset;
 169         buf = iov->iov_base + skip;
 170         copy = min(bytes, iov->iov_len - skip);
 171
 172         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
 173                 kaddr = kmap_atomic(page);
 174                 from = kaddr + offset;
 175
 176                 /* first chunk, usually the only one */
 177                 left = copyout(buf, from, copy);
 178                 copy -= left;
 179                 skip += copy;
 180                 from += copy;
 181                 bytes -= copy;
 182
 183                 while (unlikely(!left && bytes)) {
 184                         iov++;
 185                         buf = iov->iov_base;
 186                         copy = min(bytes, iov->iov_len);
 187                         left = copyout(buf, from, copy);
 188                         copy -= left;
 189                         skip = copy;
 190                         from += copy;
 191                         bytes -= copy;
 192                 }
 193                 if (likely(!bytes)) {
 194                         kunmap_atomic(kaddr);
 195                         goto done;
 196                 }
 197                 offset = from - kaddr;
 198                 buf += copy;
 199                 kunmap_atomic(kaddr);
 200                 copy = min(bytes, iov->iov_len - skip);
 201         }
 202         /* Too bad - revert to non-atomic kmap */
 203
 204         kaddr = kmap(page);
 205         from = kaddr + offset;
 206         left = copyout(buf, from, copy);
 207         copy -= left;
 208         skip += copy;
 209         from += copy;
 210         bytes -= copy;
 211         while (unlikely(!left && bytes)) {
 212                 iov++;
 213                 buf = iov->iov_base;
 214                 copy = min(bytes, iov->iov_len);
 215                 left = copyout(buf, from, copy);
 216                 copy -= left;
 217                 skip = copy;
 218                 from += copy;
 219                 bytes -= copy;
 220         }
 221         kunmap(page);
 222
 223 done:
 224         if (skip == iov->iov_len) {
 225                 iov++;
 226                 skip = 0;
 227         }
 228         i->count -= wanted - bytes;
 229         i->nr_segs -= iov - i->iov;
 230         i->iov = iov;
 231         i->iov_offset = skip;
 232         return wanted - bytes;
 233 }
 234
 235 static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
 236                          struct iov_iter *i)
 237 {
 238         size_t skip, copy, left, wanted;
 239         const struct iovec *iov;
 240         char __user *buf;
 241         void *kaddr, *to;
 242
 243         if (unlikely(bytes > i->count))
 244                 bytes = i->count;
 245
 246         if (unlikely(!bytes))
 247                 return 0;
 248
 249         might_fault();
 250         wanted = bytes;
 251         iov = i->iov;
 252         skip = i->iov_offset;
 253         buf = iov->iov_base + skip;
 254         copy = min(bytes, iov->iov_len - skip);
 255
 256         if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
 257                 kaddr = kmap_atomic(page);
 258                 to = kaddr + offset;
 259
 260                 /* first chunk, usually the only one */
 261                 left = copyin(to, buf, copy);
 262                 copy -= left;
 263                 skip += copy;
 264                 to += copy;
 265                 bytes -= copy;
 266
 267                 while (unlikely(!left && bytes)) {
 268                         iov++;
 269                         buf = iov->iov_base;
 270                         copy = min(bytes, iov->iov_len);
 271                         left = copyin(to, buf, copy);
 272                         copy -= left;
 273                         skip = copy;
 274                         to += copy;
 275                         bytes -= copy;
 276                 }
 277                 if (likely(!bytes)) {
 278                         kunmap_atomic(kaddr);
 279                         goto done;
 280                 }
 281                 offset = to - kaddr;
 282                 buf += copy;
 283                 kunmap_atomic(kaddr);
 284                 copy = min(bytes, iov->iov_len - skip);
 285         }
 286         /* Too bad - revert to non-atomic kmap */
 287
 288         kaddr = kmap(page);
 289         to = kaddr + offset;
 290         left = copyin(to, buf, copy);
 291         copy -= left;
 292         skip += copy;
 293         to += copy;
 294         bytes -= copy;
 295         while (unlikely(!left && bytes)) {
 296                 iov++;
 297                 buf = iov->iov_base;
 298                 copy = min(bytes, iov->iov_len);
 299                 left = copyin(to, buf, copy);
 300                 copy -= left;
 301                 skip = copy;
 302                 to += copy;
 303                 bytes -= copy;
 304         }
 305         kunmap(page);
 306
 307 done:
 308         if (skip == iov->iov_len) {
 309                 iov++;
 310                 skip = 0;
 311         }
 312         i->count -= wanted - bytes;
 313         i->nr_segs -= iov - i->iov;
 314         i->iov = iov;
 315         i->iov_offset = skip;
 316         return wanted - bytes;
 317 }
 318
 319 #ifdef PIPE_PARANOIA
 320 static bool sanity(const struct iov_iter *i)
 321 {
 322         struct pipe_inode_info *pipe = i->pipe;
 323         int idx = i->idx;
 324         int next = pipe->curbuf + pipe->nrbufs;
 325         if (i->iov_offset) {
 326                 struct pipe_buffer *p;
 327                 if (unlikely(!pipe->nrbufs))
 328                         goto Bad;       // pipe must be non-empty
 329                 if (unlikely(idx != ((next - 1) & (pipe->buffers - 1))))
 330                         goto Bad;       // must be at the last buffer...
 331
 332                 p = &pipe->bufs[idx];
 333                 if (unlikely(p->offset + p->len != i->iov_offset))
 334                         goto Bad;       // ... at the end of segment
 335         } else {
 336                 if (idx != (next & (pipe->buffers - 1)))
 337                         goto Bad;       // must be right after the last buffer
 338         }
 339         return true;
 340 Bad:
 341         printk(KERN_ERR "idx = %d, offset = %zd\n", i->idx, i->iov_offset);
 342         printk(KERN_ERR "curbuf = %d, nrbufs = %d, buffers = %d\n",
 343                         pipe->curbuf, pipe->nrbufs, pipe->buffers);
 344         for (idx = 0; idx < pipe->buffers; idx++)
 345                 printk(KERN_ERR "[%p %p %d %d]\n",
 346                         pipe->bufs[idx].ops,
 347                         pipe->bufs[idx].page,
 348                         pipe->bufs[idx].offset,
 349                         pipe->bufs[idx].len);
 350         WARN_ON(1);
 351         return false;
 352 }
 353 #else
 354 #define sanity(i) true
 355 #endif
 356
 357 static inline int next_idx(int idx, struct pipe_inode_info *pipe)
 358 {
 359         return (idx + 1) & (pipe->buffers - 1);
 360 }
 361
 362 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
 363                          struct iov_iter *i)
 364 {
 365         struct pipe_inode_info *pipe = i->pipe;
 366         struct pipe_buffer *buf;
 367         size_t off;
 368         int idx;
 369
 370         if (unlikely(bytes > i->count))
 371                 bytes = i->count;
 372
 373         if (unlikely(!bytes))
 374                 return 0;
 375
 376         if (!sanity(i))
 377                 return 0;
 378
 379         off = i->iov_offset;
 380         idx = i->idx;
 381         buf = &pipe->bufs[idx];
 382         if (off) {
 383                 if (offset == off && buf->page == page) {
 384                         /* merge with the last one */
 385                         buf->len += bytes;
 386                         i->iov_offset += bytes;
 387                         goto out;
 388                 }
 389                 idx = next_idx(idx, pipe);
 390                 buf = &pipe->bufs[idx];
 391         }
 392         if (idx == pipe->curbuf && pipe->nrbufs)
 393                 return 0;
 394         pipe->nrbufs++;
 395         buf->ops = &page_cache_pipe_buf_ops;
 396         get_page(buf->page = page);
 397         buf->offset = offset;
 398         buf->len = bytes;
 399         i->iov_offset = offset + bytes;
 400         i->idx = idx;
 401 out:
 402         i->count -= bytes;
 403         return bytes;
 404 }
 405
 406 /*
 407  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 408  * bytes.  For each iovec, fault in each page that constitutes the iovec.
 409  *
 410  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 411  * because it is an invalid address).
 412  */
 413 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 414 {
 415         size_t skip = i->iov_offset;
 416         const struct iovec *iov;
 417         int err;
 418         struct iovec v;
 419
 420         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 421                 iterate_iovec(i, bytes, v, iov, skip, ({
 422                         err = fault_in_pages_readable(v.iov_base, v.iov_len);
 423                         if (unlikely(err))
 424                         return err;
 425                 0;}))
 426         }
 427         return 0;
 428 }
 429 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 430
 431 void iov_iter_init(struct iov_iter *i, int direction,
 432                         const struct iovec *iov, unsigned long nr_segs,
 433                         size_t count)
 434 {
 435         /* It will get better.  Eventually... */
 436         if (uaccess_kernel()) {
 437                 direction |= ITER_KVEC;
 438                 i->type = direction;
 439                 i->kvec = (struct kvec *)iov;
 440         } else {
 441                 i->type = direction;
 442                 i->iov = iov;
 443         }
 444         i->nr_segs = nr_segs;
 445         i->iov_offset = 0;
 446         i->count = count;
 447 }
 448 EXPORT_SYMBOL(iov_iter_init);
 449
 450 static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
 451 {
 452         char *from = kmap_atomic(page);
 453         memcpy(to, from + offset, len);
 454         kunmap_atomic(from);
 455 }
 456
 457 static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
 458 {
 459         char *to = kmap_atomic(page);
 460         memcpy(to + offset, from, len);
 461         kunmap_atomic(to);
 462 }
 463
 464 static void memzero_page(struct page *page, size_t offset, size_t len)
 465 {
 466         char *addr = kmap_atomic(page);
 467         memset(addr + offset, 0, len);
 468         kunmap_atomic(addr);
 469 }
 470
 471 static inline bool allocated(struct pipe_buffer *buf)
 472 {
 473         return buf->ops == &default_pipe_buf_ops;
 474 }
 475
 476 static inline void data_start(const struct iov_iter *i, int *idxp, size_t *offp)
 477 {
 478         size_t off = i->iov_offset;
 479         int idx = i->idx;
 480         if (off && (!allocated(&i->pipe->bufs[idx]) || off == PAGE_SIZE)) {
 481                 idx = next_idx(idx, i->pipe);
 482                 off = 0;
 483         }
 484         *idxp = idx;
 485         *offp = off;
 486 }
 487
 488 static size_t push_pipe(struct iov_iter *i, size_t size,
 489                         int *idxp, size_t *offp)
 490 {
 491         struct pipe_inode_info *pipe = i->pipe;
 492         size_t off;
 493         int idx;
 494         ssize_t left;
 495
 496         if (unlikely(size > i->count))
 497                 size = i->count;
 498         if (unlikely(!size))
 499                 return 0;
 500
 501         left = size;
 502         data_start(i, &idx, &off);
 503         *idxp = idx;
 504         *offp = off;
 505         if (off) {
 506                 left -= PAGE_SIZE - off;
 507                 if (left <= 0) {
 508                         pipe->bufs[idx].len += size;
 509                         return size;
 510                 }
 511                 pipe->bufs[idx].len = PAGE_SIZE;
 512                 idx = next_idx(idx, pipe);
 513         }
 514         while (idx != pipe->curbuf || !pipe->nrbufs) {
 515                 struct page *page = alloc_page(GFP_USER);
 516                 if (!page)
 517                         break;
 518                 pipe->nrbufs++;
 519                 pipe->bufs[idx].ops = &default_pipe_buf_ops;
 520                 pipe->bufs[idx].page = page;
 521                 pipe->bufs[idx].offset = 0;
 522                 if (left <= PAGE_SIZE) {
 523                         pipe->bufs[idx].len = left;
 524                         return size;
 525                 }
 526                 pipe->bufs[idx].len = PAGE_SIZE;
 527                 left -= PAGE_SIZE;
 528                 idx = next_idx(idx, pipe);
 529         }
 530         return size - left;
 531 }
 532
 533 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
 534                                 struct iov_iter *i)
 535 {
 536         struct pipe_inode_info *pipe = i->pipe;
 537         size_t n, off;
 538         int idx;
 539
 540         if (!sanity(i))
 541                 return 0;
 542
 543         bytes = n = push_pipe(i, bytes, &idx, &off);
 544         if (unlikely(!n))
 545                 return 0;
 546         for ( ; n; idx = next_idx(idx, pipe), off = 0) {
 547                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 548                 memcpy_to_page(pipe->bufs[idx].page, off, addr, chunk);
 549                 i->idx = idx;
 550                 i->iov_offset = off + chunk;
 551                 n -= chunk;
 552                 addr += chunk;
 553         }
 554         i->count -= bytes;
 555         return bytes;
 556 }
 557
 558 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 559 {
 560         const char *from = addr;
 561         if (unlikely(i->type & ITER_PIPE))
 562                 return copy_pipe_to_iter(addr, bytes, i);
 563         if (iter_is_iovec(i))
 564                 might_fault();
 565         iterate_and_advance(i, bytes, v,
 566                 copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
 567                 memcpy_to_page(v.bv_page, v.bv_offset,
 568                                (from += v.bv_len) - v.bv_len, v.bv_len),
 569                 memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
 570         )
 571
 572         return bytes;
 573 }
 574 EXPORT_SYMBOL(_copy_to_iter);
 575
 576 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 577 {
 578         char *to = addr;
 579         if (unlikely(i->type & ITER_PIPE)) {
 580                 WARN_ON(1);
 581                 return 0;
 582         }
 583         if (iter_is_iovec(i))
 584                 might_fault();
 585         iterate_and_advance(i, bytes, v,
 586                 copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 587                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 588                                  v.bv_offset, v.bv_len),
 589                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 590         )
 591
 592         return bytes;
 593 }
 594 EXPORT_SYMBOL(_copy_from_iter);
 595
 596 bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 597 {
 598         char *to = addr;
 599         if (unlikely(i->type & ITER_PIPE)) {
 600                 WARN_ON(1);
 601                 return false;
 602         }
 603         if (unlikely(i->count < bytes))
 604                 return false;
 605
 606         if (iter_is_iovec(i))
 607                 might_fault();
 608         iterate_all_kinds(i, bytes, v, ({
 609                 if (copyin((to += v.iov_len) - v.iov_len,
 610                                       v.iov_base, v.iov_len))
 611                         return false;
 612                 0;}),
 613                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 614                                  v.bv_offset, v.bv_len),
 615                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 616         )
 617
 618         iov_iter_advance(i, bytes);
 619         return true;
 620 }
 621 EXPORT_SYMBOL(_copy_from_iter_full);
 622
 623 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 624 {
 625         char *to = addr;
 626         if (unlikely(i->type & ITER_PIPE)) {
 627                 WARN_ON(1);
 628                 return 0;
 629         }
 630         iterate_and_advance(i, bytes, v,
 631                 __copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 632                                          v.iov_base, v.iov_len),
 633                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 634                                  v.bv_offset, v.bv_len),
 635                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 636         )
 637
 638         return bytes;
 639 }
 640 EXPORT_SYMBOL(_copy_from_iter_nocache);
 641
 642 bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 643 {
 644         char *to = addr;
 645         if (unlikely(i->type & ITER_PIPE)) {
 646                 WARN_ON(1);
 647                 return false;
 648         }
 649         if (unlikely(i->count < bytes))
 650                 return false;
 651         iterate_all_kinds(i, bytes, v, ({
 652                 if (__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
 653                                              v.iov_base, v.iov_len))
 654                         return false;
 655                 0;}),
 656                 memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 657                                  v.bv_offset, v.bv_len),
 658                 memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 659         )
 660
 661         iov_iter_advance(i, bytes);
 662         return true;
 663 }
 664 EXPORT_SYMBOL(_copy_from_iter_full_nocache);
 665
 666 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 667 {
 668         size_t v = n + offset;
 669         if (likely(n <= v && v <= (PAGE_SIZE << compound_order(page))))
 670                 return true;
 671         WARN_ON(1);
 672         return false;
 673 }
 674
 675 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 676                          struct iov_iter *i)
 677 {
 678         if (unlikely(!page_copy_sane(page, offset, bytes)))
 679                 return 0;
 680         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 681                 void *kaddr = kmap_atomic(page);
 682                 size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 683                 kunmap_atomic(kaddr);
 684                 return wanted;
 685         } else if (likely(!(i->type & ITER_PIPE)))
 686                 return copy_page_to_iter_iovec(page, offset, bytes, i);
 687         else
 688                 return copy_page_to_iter_pipe(page, offset, bytes, i);
 689 }
 690 EXPORT_SYMBOL(copy_page_to_iter);
 691
 692 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 693                          struct iov_iter *i)
 694 {
 695         if (unlikely(!page_copy_sane(page, offset, bytes)))
 696                 return 0;
 697         if (unlikely(i->type & ITER_PIPE)) {
 698                 WARN_ON(1);
 699                 return 0;
 700         }
 701         if (i->type & (ITER_BVEC|ITER_KVEC)) {
 702                 void *kaddr = kmap_atomic(page);
 703                 size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
 704                 kunmap_atomic(kaddr);
 705                 return wanted;
 706         } else
 707                 return copy_page_from_iter_iovec(page, offset, bytes, i);
 708 }
 709 EXPORT_SYMBOL(copy_page_from_iter);
 710
 711 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
 712 {
 713         struct pipe_inode_info *pipe = i->pipe;
 714         size_t n, off;
 715         int idx;
 716
 717         if (!sanity(i))
 718                 return 0;
 719
 720         bytes = n = push_pipe(i, bytes, &idx, &off);
 721         if (unlikely(!n))
 722                 return 0;
 723
 724         for ( ; n; idx = next_idx(idx, pipe), off = 0) {
 725                 size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
 726                 memzero_page(pipe->bufs[idx].page, off, chunk);
 727                 i->idx = idx;
 728                 i->iov_offset = off + chunk;
 729                 n -= chunk;
 730         }
 731         i->count -= bytes;
 732         return bytes;
 733 }
 734
 735 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 736 {
 737         if (unlikely(i->type & ITER_PIPE))
 738                 return pipe_zero(bytes, i);
 739         iterate_and_advance(i, bytes, v,
 740                 clear_user(v.iov_base, v.iov_len),
 741                 memzero_page(v.bv_page, v.bv_offset, v.bv_len),
 742                 memset(v.iov_base, 0, v.iov_len)
 743         )
 744
 745         return bytes;
 746 }
 747 EXPORT_SYMBOL(iov_iter_zero);
 748
 749 size_t iov_iter_copy_from_user_atomic(struct page *page,
 750                 struct iov_iter *i, unsigned long offset, size_t bytes)
 751 {
 752         char *kaddr = kmap_atomic(page), *p = kaddr + offset;
 753         if (unlikely(!page_copy_sane(page, offset, bytes))) {
 754                 kunmap_atomic(kaddr);
 755                 return 0;
 756         }
 757         if (unlikely(i->type & ITER_PIPE)) {
 758                 kunmap_atomic(kaddr);
 759                 WARN_ON(1);
 760                 return 0;
 761         }
 762         iterate_all_kinds(i, bytes, v,
 763                 copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 764                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 765                                  v.bv_offset, v.bv_len),
 766                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 767         )
 768         kunmap_atomic(kaddr);
 769         return bytes;
 770 }
 771 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 772
 773 static inline void pipe_truncate(struct iov_iter *i)
 774 {
 775         struct pipe_inode_info *pipe = i->pipe;
 776         if (pipe->nrbufs) {
 777                 size_t off = i->iov_offset;
 778                 int idx = i->idx;
 779                 int nrbufs = (idx - pipe->curbuf) & (pipe->buffers - 1);
 780                 if (off) {
 781                         pipe->bufs[idx].len = off - pipe->bufs[idx].offset;
 782                         idx = next_idx(idx, pipe);
 783                         nrbufs++;
 784                 }
 785                 while (pipe->nrbufs > nrbufs) {
 786                         pipe_buf_release(pipe, &pipe->bufs[idx]);
 787                         idx = next_idx(idx, pipe);
 788                         pipe->nrbufs--;
 789                 }
 790         }
 791 }
 792
 793 static void pipe_advance(struct iov_iter *i, size_t size)
 794 {
 795         struct pipe_inode_info *pipe = i->pipe;
 796         if (unlikely(i->count < size))
 797                 size = i->count;
 798         if (size) {
 799                 struct pipe_buffer *buf;
 800                 size_t off = i->iov_offset, left = size;
 801                 int idx = i->idx;
 802                 if (off) /* make it relative to the beginning of buffer */
 803                         left += off - pipe->bufs[idx].offset;
 804                 while (1) {
 805                         buf = &pipe->bufs[idx];
 806                         if (left <= buf->len)
 807                                 break;
 808                         left -= buf->len;
 809                         idx = next_idx(idx, pipe);
 810                 }
 811                 i->idx = idx;
 812                 i->iov_offset = buf->offset + left;
 813         }
 814         i->count -= size;
 815         /* ... and discard everything past that point */
 816         pipe_truncate(i);
 817 }
 818
 819 void iov_iter_advance(struct iov_iter *i, size_t size)
 820 {
 821         if (unlikely(i->type & ITER_PIPE)) {
 822                 pipe_advance(i, size);
 823                 return;
 824         }
 825         iterate_and_advance(i, size, v, 0, 0, 0)
 826 }
 827 EXPORT_SYMBOL(iov_iter_advance);
 828
 829 void iov_iter_revert(struct iov_iter *i, size_t unroll)
 830 {
 831         if (!unroll)
 832                 return;
 833         if (WARN_ON(unroll > MAX_RW_COUNT))
 834                 return;
 835         i->count += unroll;
 836         if (unlikely(i->type & ITER_PIPE)) {
 837                 struct pipe_inode_info *pipe = i->pipe;
 838                 int idx = i->idx;
 839                 size_t off = i->iov_offset;
 840                 while (1) {
 841                         size_t n = off - pipe->bufs[idx].offset;
 842                         if (unroll < n) {
 843                                 off -= unroll;
 844                                 break;
 845                         }
 846                         unroll -= n;
 847                         if (!unroll && idx == i->start_idx) {
 848                                 off = 0;
 849                                 break;
 850                         }
 851                         if (!idx--)
 852                                 idx = pipe->buffers - 1;
 853                         off = pipe->bufs[idx].offset + pipe->bufs[idx].len;
 854                 }
 855                 i->iov_offset = off;
 856                 i->idx = idx;
 857                 pipe_truncate(i);
 858                 return;
 859         }
 860         if (unroll <= i->iov_offset) {
 861                 i->iov_offset -= unroll;
 862                 return;
 863         }
 864         unroll -= i->iov_offset;
 865         if (i->type & ITER_BVEC) {
 866                 const struct bio_vec *bvec = i->bvec;
 867                 while (1) {
 868                         size_t n = (--bvec)->bv_len;
 869                         i->nr_segs++;
 870                         if (unroll <= n) {
 871                                 i->bvec = bvec;
 872                                 i->iov_offset = n - unroll;
 873                                 return;
 874                         }
 875                         unroll -= n;
 876                 }
 877         } else { /* same logics for iovec and kvec */
 878                 const struct iovec *iov = i->iov;
 879                 while (1) {
 880                         size_t n = (--iov)->iov_len;
 881                         i->nr_segs++;
 882                         if (unroll <= n) {
 883                                 i->iov = iov;
 884                                 i->iov_offset = n - unroll;
 885                                 return;
 886                         }
 887                         unroll -= n;
 888                 }
 889         }
 890 }
 891 EXPORT_SYMBOL(iov_iter_revert);
 892
 893 /*
 894  * Return the count of just the current iov_iter segment.
 895  */
 896 size_t iov_iter_single_seg_count(const struct iov_iter *i)
 897 {
 898         if (unlikely(i->type & ITER_PIPE))
 899                 return i->count;        // it is a silly place, anyway
 900         if (i->nr_segs == 1)
 901                 return i->count;
 902         else if (i->type & ITER_BVEC)
 903                 return min(i->count, i->bvec->bv_len - i->iov_offset);
 904         else
 905                 return min(i->count, i->iov->iov_len - i->iov_offset);
 906 }
 907 EXPORT_SYMBOL(iov_iter_single_seg_count);
 908
 909 void iov_iter_kvec(struct iov_iter *i, int direction,
 910                         const struct kvec *kvec, unsigned long nr_segs,
 911                         size_t count)
 912 {
 913         BUG_ON(!(direction & ITER_KVEC));
 914         i->type = direction;
 915         i->kvec = kvec;
 916         i->nr_segs = nr_segs;
 917         i->iov_offset = 0;
 918         i->count = count;
 919 }
 920 EXPORT_SYMBOL(iov_iter_kvec);
 921
 922 void iov_iter_bvec(struct iov_iter *i, int direction,
 923                         const struct bio_vec *bvec, unsigned long nr_segs,
 924                         size_t count)
 925 {
 926         BUG_ON(!(direction & ITER_BVEC));
 927         i->type = direction;
 928         i->bvec = bvec;
 929         i->nr_segs = nr_segs;
 930         i->iov_offset = 0;
 931         i->count = count;
 932 }
 933 EXPORT_SYMBOL(iov_iter_bvec);
 934
 935 void iov_iter_pipe(struct iov_iter *i, int direction,
 936                         struct pipe_inode_info *pipe,
 937                         size_t count)
 938 {
 939         BUG_ON(direction != ITER_PIPE);
 940         WARN_ON(pipe->nrbufs == pipe->buffers);
 941         i->type = direction;
 942         i->pipe = pipe;
 943         i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 944         i->iov_offset = 0;
 945         i->count = count;
 946         i->start_idx = i->idx;
 947 }
 948 EXPORT_SYMBOL(iov_iter_pipe);
 949
 950 unsigned long iov_iter_alignment(const struct iov_iter *i)
 951 {
 952         unsigned long res = 0;
 953         size_t size = i->count;
 954
 955         if (unlikely(i->type & ITER_PIPE)) {
 956                 if (size && i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
 957                         return size | i->iov_offset;
 958                 return size;
 959         }
 960         iterate_all_kinds(i, size, v,
 961                 (res |= (unsigned long)v.iov_base | v.iov_len, 0),
 962                 res |= v.bv_offset | v.bv_len,
 963                 res |= (unsigned long)v.iov_base | v.iov_len
 964         )
 965         return res;
 966 }
 967 EXPORT_SYMBOL(iov_iter_alignment);
 968
 969 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 970 {
 971         unsigned long res = 0;
 972         size_t size = i->count;
 973
 974         if (unlikely(i->type & ITER_PIPE)) {
 975                 WARN_ON(1);
 976                 return ~0U;
 977         }
 978
 979         iterate_all_kinds(i, size, v,
 980                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
 981                         (size != v.iov_len ? size : 0), 0),
 982                 (res |= (!res ? 0 : (unsigned long)v.bv_offset) |
 983                         (size != v.bv_len ? size : 0)),
 984                 (res |= (!res ? 0 : (unsigned long)v.iov_base) |
 985                         (size != v.iov_len ? size : 0))
 986                 );
 987         return res;
 988 }
 989 EXPORT_SYMBOL(iov_iter_gap_alignment);
 990
 991 static inline size_t __pipe_get_pages(struct iov_iter *i,
 992                                 size_t maxsize,
 993                                 struct page **pages,
 994                                 int idx,
 995                                 size_t *start)
 996 {
 997         struct pipe_inode_info *pipe = i->pipe;
 998         ssize_t n = push_pipe(i, maxsize, &idx, start);
 999         if (!n)
1000                 return -EFAULT;
1001
1002         maxsize = n;
1003         n += *start;
1004         while (n > 0) {
1005                 get_page(*pages++ = pipe->bufs[idx].page);
1006                 idx = next_idx(idx, pipe);
1007                 n -= PAGE_SIZE;
1008         }
1009
1010         return maxsize;
1011 }
1012
1013 static ssize_t pipe_get_pages(struct iov_iter *i,
1014                    struct page **pages, size_t maxsize, unsigned maxpages,
1015                    size_t *start)
1016 {
1017         unsigned npages;
1018         size_t capacity;
1019         int idx;
1020
1021         if (!maxsize)
1022                 return 0;
1023
1024         if (!sanity(i))
1025                 return -EFAULT;
1026
1027         data_start(i, &idx, start);
1028         /* some of this one + all after this one */
1029         npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
1030         capacity = min(npages,maxpages) * PAGE_SIZE - *start;
1031
1032         return __pipe_get_pages(i, min(maxsize, capacity), pages, idx, start);
1033 }
1034
1035 ssize_t iov_iter_get_pages(struct iov_iter *i,
1036                    struct page **pages, size_t maxsize, unsigned maxpages,
1037                    size_t *start)
1038 {
1039         if (maxsize > i->count)
1040                 maxsize = i->count;
1041
1042         if (unlikely(i->type & ITER_PIPE))
1043                 return pipe_get_pages(i, pages, maxsize, maxpages, start);
1044         iterate_all_kinds(i, maxsize, v, ({
1045                 unsigned long addr = (unsigned long)v.iov_base;
1046                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1047                 int n;
1048                 int res;
1049
1050                 if (len > maxpages * PAGE_SIZE)
1051                         len = maxpages * PAGE_SIZE;
1052                 addr &= ~(PAGE_SIZE - 1);
1053                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1054                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
1055                 if (unlikely(res < 0))
1056                         return res;
1057                 return (res == n ? len : res * PAGE_SIZE) - *start;
1058         0;}),({
1059                 /* can't be more than PAGE_SIZE */
1060                 *start = v.bv_offset;
1061                 get_page(*pages = v.bv_page);
1062                 return v.bv_len;
1063         }),({
1064                 return -EFAULT;
1065         })
1066         )
1067         return 0;
1068 }
1069 EXPORT_SYMBOL(iov_iter_get_pages);
1070
1071 static struct page **get_pages_array(size_t n)
1072 {
1073         return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
1074 }
1075
1076 static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
1077                    struct page ***pages, size_t maxsize,
1078                    size_t *start)
1079 {
1080         struct page **p;
1081         size_t n;
1082         int idx;
1083         int npages;
1084
1085         if (!maxsize)
1086                 return 0;
1087
1088         if (!sanity(i))
1089                 return -EFAULT;
1090
1091         data_start(i, &idx, start);
1092         /* some of this one + all after this one */
1093         npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
1094         n = npages * PAGE_SIZE - *start;
1095         if (maxsize > n)
1096                 maxsize = n;
1097         else
1098                 npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
1099         p = get_pages_array(npages);
1100         if (!p)
1101                 return -ENOMEM;
1102         n = __pipe_get_pages(i, maxsize, p, idx, start);
1103         if (n > 0)
1104                 *pages = p;
1105         else
1106                 kvfree(p);
1107         return n;
1108 }
1109
1110 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
1111                    struct page ***pages, size_t maxsize,
1112                    size_t *start)
1113 {
1114         struct page **p;
1115
1116         if (maxsize > i->count)
1117                 maxsize = i->count;
1118
1119         if (unlikely(i->type & ITER_PIPE))
1120                 return pipe_get_pages_alloc(i, pages, maxsize, start);
1121         iterate_all_kinds(i, maxsize, v, ({
1122                 unsigned long addr = (unsigned long)v.iov_base;
1123                 size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
1124                 int n;
1125                 int res;
1126
1127                 addr &= ~(PAGE_SIZE - 1);
1128                 n = DIV_ROUND_UP(len, PAGE_SIZE);
1129                 p = get_pages_array(n);
1130                 if (!p)
1131                         return -ENOMEM;
1132                 res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
1133                 if (unlikely(res < 0)) {
1134                         kvfree(p);
1135                         return res;
1136                 }
1137                 *pages = p;
1138                 return (res == n ? len : res * PAGE_SIZE) - *start;
1139         0;}),({
1140                 /* can't be more than PAGE_SIZE */
1141                 *start = v.bv_offset;
1142                 *pages = p = get_pages_array(1);
1143                 if (!p)
1144                         return -ENOMEM;
1145                 get_page(*p = v.bv_page);
1146                 return v.bv_len;
1147         }),({
1148                 return -EFAULT;
1149         })
1150         )
1151         return 0;
1152 }
1153 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
1154
1155 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1156                                struct iov_iter *i)
1157 {
1158         char *to = addr;
1159         __wsum sum, next;
1160         size_t off = 0;
1161         sum = *csum;
1162         if (unlikely(i->type & ITER_PIPE)) {
1163                 WARN_ON(1);
1164                 return 0;
1165         }
1166         iterate_and_advance(i, bytes, v, ({
1167                 int err = 0;
1168                 next = csum_and_copy_from_user(v.iov_base,
1169                                                (to += v.iov_len) - v.iov_len,
1170                                                v.iov_len, 0, &err);
1171                 if (!err) {
1172                         sum = csum_block_add(sum, next, off);
1173                         off += v.iov_len;
1174                 }
1175                 err ? v.iov_len : 0;
1176         }), ({
1177                 char *p = kmap_atomic(v.bv_page);
1178                 next = csum_partial_copy_nocheck(p + v.bv_offset,
1179                                                  (to += v.bv_len) - v.bv_len,
1180                                                  v.bv_len, 0);
1181                 kunmap_atomic(p);
1182                 sum = csum_block_add(sum, next, off);
1183                 off += v.bv_len;
1184         }),({
1185                 next = csum_partial_copy_nocheck(v.iov_base,
1186                                                  (to += v.iov_len) - v.iov_len,
1187                                                  v.iov_len, 0);
1188                 sum = csum_block_add(sum, next, off);
1189                 off += v.iov_len;
1190         })
1191         )
1192         *csum = sum;
1193         return bytes;
1194 }
1195 EXPORT_SYMBOL(csum_and_copy_from_iter);
1196
1197 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
1198                                struct iov_iter *i)
1199 {
1200         char *to = addr;
1201         __wsum sum, next;
1202         size_t off = 0;
1203         sum = *csum;
1204         if (unlikely(i->type & ITER_PIPE)) {
1205                 WARN_ON(1);
1206                 return false;
1207         }
1208         if (unlikely(i->count < bytes))
1209                 return false;
1210         iterate_all_kinds(i, bytes, v, ({
1211                 int err = 0;
1212                 next = csum_and_copy_from_user(v.iov_base,
1213                                                (to += v.iov_len) - v.iov_len,
1214                                                v.iov_len, 0, &err);
1215                 if (err)
1216                         return false;
1217                 sum = csum_block_add(sum, next, off);
1218                 off += v.iov_len;
1219                 0;
1220         }), ({
1221                 char *p = kmap_atomic(v.bv_page);
1222                 next = csum_partial_copy_nocheck(p + v.bv_offset,
1223                                                  (to += v.bv_len) - v.bv_len,
1224                                                  v.bv_len, 0);
1225                 kunmap_atomic(p);
1226                 sum = csum_block_add(sum, next, off);
1227                 off += v.bv_len;
1228         }),({
1229                 next = csum_partial_copy_nocheck(v.iov_base,
1230                                                  (to += v.iov_len) - v.iov_len,
1231                                                  v.iov_len, 0);
1232                 sum = csum_block_add(sum, next, off);
1233                 off += v.iov_len;
1234         })
1235         )
1236         *csum = sum;
1237         iov_iter_advance(i, bytes);
1238         return true;
1239 }
1240 EXPORT_SYMBOL(csum_and_copy_from_iter_full);
1241
1242 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
1243                              struct iov_iter *i)
1244 {
1245         const char *from = addr;
1246         __wsum sum, next;
1247         size_t off = 0;
1248         sum = *csum;
1249         if (unlikely(i->type & ITER_PIPE)) {
1250                 WARN_ON(1);     /* for now */
1251                 return 0;
1252         }
1253         iterate_and_advance(i, bytes, v, ({
1254                 int err = 0;
1255                 next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
1256                                              v.iov_base,
1257                                              v.iov_len, 0, &err);
1258                 if (!err) {
1259                         sum = csum_block_add(sum, next, off);
1260                         off += v.iov_len;
1261                 }
1262                 err ? v.iov_len : 0;
1263         }), ({
1264                 char *p = kmap_atomic(v.bv_page);
1265                 next = csum_partial_copy_nocheck((from += v.bv_len) - v.bv_len,
1266                                                  p + v.bv_offset,
1267                                                  v.bv_len, 0);
1268                 kunmap_atomic(p);
1269                 sum = csum_block_add(sum, next, off);
1270                 off += v.bv_len;
1271         }),({
1272                 next = csum_partial_copy_nocheck((from += v.iov_len) - v.iov_len,
1273                                                  v.iov_base,
1274                                                  v.iov_len, 0);
1275                 sum = csum_block_add(sum, next, off);
1276                 off += v.iov_len;
1277         })
1278         )
1279         *csum = sum;
1280         return bytes;
1281 }
1282 EXPORT_SYMBOL(csum_and_copy_to_iter);
1283
1284 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1285 {
1286         size_t size = i->count;
1287         int npages = 0;
1288
1289         if (!size)
1290                 return 0;
1291
1292         if (unlikely(i->type & ITER_PIPE)) {
1293                 struct pipe_inode_info *pipe = i->pipe;
1294                 size_t off;
1295                 int idx;
1296
1297                 if (!sanity(i))
1298                         return 0;
1299
1300                 data_start(i, &idx, &off);
1301                 /* some of this one + all after this one */
1302                 npages = ((pipe->curbuf - idx - 1) & (pipe->buffers - 1)) + 1;
1303                 if (npages >= maxpages)
1304                         return maxpages;
1305         } else iterate_all_kinds(i, size, v, ({
1306                 unsigned long p = (unsigned long)v.iov_base;
1307                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1308                         - p / PAGE_SIZE;
1309                 if (npages >= maxpages)
1310                         return maxpages;
1311         0;}),({
1312                 npages++;
1313                 if (npages >= maxpages)
1314                         return maxpages;
1315         }),({
1316                 unsigned long p = (unsigned long)v.iov_base;
1317                 npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
1318                         - p / PAGE_SIZE;
1319                 if (npages >= maxpages)
1320                         return maxpages;
1321         })
1322         )
1323         return npages;
1324 }
1325 EXPORT_SYMBOL(iov_iter_npages);
1326
1327 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1328 {
1329         *new = *old;
1330         if (unlikely(new->type & ITER_PIPE)) {
1331                 WARN_ON(1);
1332                 return NULL;
1333         }
1334         if (new->type & ITER_BVEC)
1335                 return new->bvec = kmemdup(new->bvec,
1336                                     new->nr_segs * sizeof(struct bio_vec),
1337                                     flags);
1338         else
1339                 /* iovec and kvec have identical layout */
1340                 return new->iov = kmemdup(new->iov,
1341                                    new->nr_segs * sizeof(struct iovec),
1342                                    flags);
1343 }
1344 EXPORT_SYMBOL(dup_iter);
1345
1346 /**
1347  * import_iovec() - Copy an array of &struct iovec from userspace
1348  *     into the kernel, check that it is valid, and initialize a new
1349  *     &struct iov_iter iterator to access it.
1350  *
1351  * @type: One of %READ or %WRITE.
1352  * @uvector: Pointer to the userspace array.
1353  * @nr_segs: Number of elements in userspace array.
1354  * @fast_segs: Number of elements in @iov.
1355  * @iov: (input and output parameter) Pointer to pointer to (usually small
1356  *     on-stack) kernel array.
1357  * @i: Pointer to iterator that will be initialized on success.
1358  *
1359  * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1360  * then this function places %NULL in *@iov on return. Otherwise, a new
1361  * array will be allocated and the result placed in *@iov. This means that
1362  * the caller may call kfree() on *@iov regardless of whether the small
1363  * on-stack array was used or not (and regardless of whether this function
1364  * returns an error or not).
1365  *
1366  * Return: 0 on success or negative error code on error.
1367  */
1368 int import_iovec(int type, const struct iovec __user * uvector,
1369                  unsigned nr_segs, unsigned fast_segs,
1370                  struct iovec **iov, struct iov_iter *i)
1371 {
1372         ssize_t n;
1373         struct iovec *p;
1374         n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1375                                   *iov, &p);
1376         if (n < 0) {
1377                 if (p != *iov)
1378                         kfree(p);
1379                 *iov = NULL;
1380                 return n;
1381         }
1382         iov_iter_init(i, type, p, nr_segs, n);
1383         *iov = p == *iov ? NULL : p;
1384         return 0;
1385 }
1386 EXPORT_SYMBOL(import_iovec);
1387
1388 #ifdef CONFIG_COMPAT
1389 #include <linux/compat.h>
1390
1391 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
1392                  unsigned nr_segs, unsigned fast_segs,
1393                  struct iovec **iov, struct iov_iter *i)
1394 {
1395         ssize_t n;
1396         struct iovec *p;
1397         n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
1398                                   *iov, &p);
1399         if (n < 0) {
1400                 if (p != *iov)
1401                         kfree(p);
1402                 *iov = NULL;
1403                 return n;
1404         }
1405         iov_iter_init(i, type, p, nr_segs, n);
1406         *iov = p == *iov ? NULL : p;
1407         return 0;
1408 }
1409 #endif
1410
1411 int import_single_range(int rw, void __user *buf, size_t len,
1412                  struct iovec *iov, struct iov_iter *i)
1413 {
1414         if (len > MAX_RW_COUNT)
1415                 len = MAX_RW_COUNT;
1416         if (unlikely(!access_ok(!rw, buf, len)))
1417                 return -EFAULT;
1418
1419         iov->iov_base = buf;
1420         iov->iov_len = len;
1421         iov_iter_init(i, rw, iov, 1, len);
1422         return 0;
1423 }
1424 EXPORT_SYMBOL(import_single_range);