1 /*- 2 * Copyright (c) 2008 Yahoo!, Inc. 3 * All rights reserved. 4 * Written by: John Baldwin <jhb@FreeBSD.org> 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the author nor the names of any co-contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #include <sys/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include <sys/param.h> 35 #include <sys/kernel.h> 36 #include <sys/bio.h> 37 #include <sys/malloc.h> 38 #include <sys/mbuf.h> 39 #include <sys/proc.h> 40 #include <sys/sglist.h> 41 #include <sys/uio.h> 42 43 #include <vm/vm.h> 44 #include <vm/vm_page.h> 45 #include <vm/pmap.h> 46 #include <vm/vm_map.h> 47 48 #include <sys/ktr.h> 49 50 static MALLOC_DEFINE(M_SGLIST, "sglist", "scatter/gather lists"); 51 52 /* 53 * Convenience macros to save the state of an sglist so it can be restored 54 * if an append attempt fails. Since sglist's only grow we only need to 55 * save the current count of segments and the length of the ending segment. 56 * Earlier segments will not be changed by an append, and the only change 57 * that can occur to the ending segment is that it can be extended. 58 */ 59 struct sgsave { 60 u_short sg_nseg; 61 size_t ss_len; 62 }; 63 64 #define SGLIST_SAVE(sg, sgsave) do { \ 65 (sgsave).sg_nseg = (sg)->sg_nseg; \ 66 if ((sgsave).sg_nseg > 0) \ 67 (sgsave).ss_len = (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len; \ 68 else \ 69 (sgsave).ss_len = 0; \ 70 } while (0) 71 72 #define SGLIST_RESTORE(sg, sgsave) do { \ 73 (sg)->sg_nseg = (sgsave).sg_nseg; \ 74 if ((sgsave).sg_nseg > 0) \ 75 (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len = (sgsave).ss_len; \ 76 } while (0) 77 78 /* 79 * Append a single (paddr, len) to a sglist. sg is the list and ss is 80 * the current segment in the list. If we run out of segments then 81 * EFBIG will be returned. 82 */ 83 static __inline int 84 _sglist_append_range(struct sglist *sg, struct sglist_seg **ssp, 85 vm_paddr_t paddr, size_t len) 86 { 87 struct sglist_seg *ss; 88 89 ss = *ssp; 90 if (ss->ss_paddr + ss->ss_len == paddr) 91 ss->ss_len += len; 92 else { 93 if (sg->sg_nseg == sg->sg_maxseg) 94 return (EFBIG); 95 ss++; 96 ss->ss_paddr = paddr; 97 ss->ss_len = len; 98 sg->sg_nseg++; 99 *ssp = ss; 100 } 101 return (0); 102 } 103 104 /* 105 * Worker routine to append a virtual address range (either kernel or 106 * user) to a scatter/gather list. 107 */ 108 static __inline int 109 _sglist_append_buf(struct sglist *sg, void *buf, size_t len, pmap_t pmap, 110 size_t *donep) 111 { 112 struct sglist_seg *ss; 113 vm_offset_t vaddr, offset; 114 vm_paddr_t paddr; 115 size_t seglen; 116 int error; 117 118 if (donep) 119 *donep = 0; 120 if (len == 0) 121 return (0); 122 123 /* Do the first page. It may have an offset. */ 124 vaddr = (vm_offset_t)buf; 125 offset = vaddr & PAGE_MASK; 126 if (pmap != NULL) 127 paddr = pmap_extract(pmap, vaddr); 128 else 129 paddr = pmap_kextract(vaddr); 130 seglen = MIN(len, PAGE_SIZE - offset); 131 if (sg->sg_nseg == 0) { 132 ss = sg->sg_segs; 133 ss->ss_paddr = paddr; 134 ss->ss_len = seglen; 135 sg->sg_nseg = 1; 136 } else { 137 ss = &sg->sg_segs[sg->sg_nseg - 1]; 138 error = _sglist_append_range(sg, &ss, paddr, seglen); 139 if (error) 140 return (error); 141 } 142 vaddr += seglen; 143 len -= seglen; 144 if (donep) 145 *donep += seglen; 146 147 while (len > 0) { 148 seglen = MIN(len, PAGE_SIZE); 149 if (pmap != NULL) 150 paddr = pmap_extract(pmap, vaddr); 151 else 152 paddr = pmap_kextract(vaddr); 153 error = _sglist_append_range(sg, &ss, paddr, seglen); 154 if (error) 155 return (error); 156 vaddr += seglen; 157 len -= seglen; 158 if (donep) 159 *donep += seglen; 160 } 161 162 return (0); 163 } 164 165 /* 166 * Determine the number of scatter/gather list elements needed to 167 * describe a kernel virtual address range. 168 */ 169 int 170 sglist_count(void *buf, size_t len) 171 { 172 vm_offset_t vaddr, vendaddr; 173 vm_paddr_t lastaddr, paddr; 174 int nsegs; 175 176 if (len == 0) 177 return (0); 178 179 vaddr = trunc_page((vm_offset_t)buf); 180 vendaddr = (vm_offset_t)buf + len; 181 nsegs = 1; 182 lastaddr = pmap_kextract(vaddr); 183 vaddr += PAGE_SIZE; 184 while (vaddr < vendaddr) { 185 paddr = pmap_kextract(vaddr); 186 if (lastaddr + PAGE_SIZE != paddr) 187 nsegs++; 188 lastaddr = paddr; 189 vaddr += PAGE_SIZE; 190 } 191 return (nsegs); 192 } 193 194 /* 195 * Determine the number of scatter/gather list elements needed to 196 * describe a buffer backed by an array of VM pages. 197 */ 198 int 199 sglist_count_vmpages(vm_page_t *m, size_t pgoff, size_t len) 200 { 201 vm_paddr_t lastaddr, paddr; 202 int i, nsegs; 203 204 if (len == 0) 205 return (0); 206 207 len += pgoff; 208 nsegs = 1; 209 lastaddr = VM_PAGE_TO_PHYS(m[0]); 210 for (i = 1; len > PAGE_SIZE; len -= PAGE_SIZE, i++) { 211 paddr = VM_PAGE_TO_PHYS(m[i]); 212 if (lastaddr + PAGE_SIZE != paddr) 213 nsegs++; 214 lastaddr = paddr; 215 } 216 return (nsegs); 217 } 218 219 /* 220 * Allocate a scatter/gather list along with 'nsegs' segments. The 221 * 'mflags' parameters are the same as passed to malloc(9). The caller 222 * should use sglist_free() to free this list. 223 */ 224 struct sglist * 225 sglist_alloc(int nsegs, int mflags) 226 { 227 struct sglist *sg; 228 229 sg = malloc(sizeof(struct sglist) + nsegs * sizeof(struct sglist_seg), 230 M_SGLIST, mflags); 231 if (sg == NULL) 232 return (NULL); 233 sglist_init(sg, nsegs, (struct sglist_seg *)(sg + 1)); 234 return (sg); 235 } 236 237 /* 238 * Free a scatter/gather list allocated via sglist_allc(). 239 */ 240 void 241 sglist_free(struct sglist *sg) 242 { 243 244 if (sg == NULL) 245 return; 246 247 if (refcount_release(&sg->sg_refs)) 248 free(sg, M_SGLIST); 249 } 250 251 /* 252 * Append the segments to describe a single kernel virtual address 253 * range to a scatter/gather list. If there are insufficient 254 * segments, then this fails with EFBIG. 255 */ 256 int 257 sglist_append(struct sglist *sg, void *buf, size_t len) 258 { 259 struct sgsave save; 260 int error; 261 262 if (sg->sg_maxseg == 0) 263 return (EINVAL); 264 SGLIST_SAVE(sg, save); 265 error = _sglist_append_buf(sg, buf, len, NULL, NULL); 266 if (error) 267 SGLIST_RESTORE(sg, save); 268 return (error); 269 } 270 271 /* 272 * Append the segments to describe a bio's data to a scatter/gather list. 273 * If there are insufficient segments, then this fails with EFBIG. 274 * 275 * NOTE: This function expects bio_bcount to be initialized. 276 */ 277 int 278 sglist_append_bio(struct sglist *sg, struct bio *bp) 279 { 280 int error; 281 282 if ((bp->bio_flags & BIO_UNMAPPED) == 0) 283 error = sglist_append(sg, bp->bio_data, bp->bio_bcount); 284 else 285 error = sglist_append_vmpages(sg, bp->bio_ma, 286 bp->bio_ma_offset, bp->bio_bcount); 287 return (error); 288 } 289 290 /* 291 * Append a single physical address range to a scatter/gather list. 292 * If there are insufficient segments, then this fails with EFBIG. 293 */ 294 int 295 sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len) 296 { 297 struct sglist_seg *ss; 298 struct sgsave save; 299 int error; 300 301 if (sg->sg_maxseg == 0) 302 return (EINVAL); 303 if (len == 0) 304 return (0); 305 306 if (sg->sg_nseg == 0) { 307 sg->sg_segs[0].ss_paddr = paddr; 308 sg->sg_segs[0].ss_len = len; 309 sg->sg_nseg = 1; 310 return (0); 311 } 312 ss = &sg->sg_segs[sg->sg_nseg - 1]; 313 SGLIST_SAVE(sg, save); 314 error = _sglist_append_range(sg, &ss, paddr, len); 315 if (error) 316 SGLIST_RESTORE(sg, save); 317 return (error); 318 } 319 320 /* 321 * Append the segments that describe a single mbuf chain to a 322 * scatter/gather list. If there are insufficient segments, then this 323 * fails with EFBIG. 324 */ 325 int 326 sglist_append_mbuf(struct sglist *sg, struct mbuf *m0) 327 { 328 struct sgsave save; 329 struct mbuf *m; 330 int error; 331 332 if (sg->sg_maxseg == 0) 333 return (EINVAL); 334 335 error = 0; 336 SGLIST_SAVE(sg, save); 337 for (m = m0; m != NULL; m = m->m_next) { 338 if (m->m_len > 0) { 339 error = sglist_append(sg, m->m_data, m->m_len); 340 if (error) { 341 SGLIST_RESTORE(sg, save); 342 return (error); 343 } 344 } 345 } 346 return (0); 347 } 348 349 /* 350 * Append the segments that describe a buffer spanning an array of VM 351 * pages. The buffer begins at an offset of 'pgoff' in the first 352 * page. 353 */ 354 int 355 sglist_append_vmpages(struct sglist *sg, vm_page_t *m, size_t pgoff, 356 size_t len) 357 { 358 struct sgsave save; 359 struct sglist_seg *ss; 360 vm_paddr_t paddr; 361 size_t seglen; 362 int error, i; 363 364 if (sg->sg_maxseg == 0) 365 return (EINVAL); 366 if (len == 0) 367 return (0); 368 369 SGLIST_SAVE(sg, save); 370 i = 0; 371 if (sg->sg_nseg == 0) { 372 seglen = min(PAGE_SIZE - pgoff, len); 373 sg->sg_segs[0].ss_paddr = VM_PAGE_TO_PHYS(m[0]) + pgoff; 374 sg->sg_segs[0].ss_len = seglen; 375 sg->sg_nseg = 1; 376 pgoff = 0; 377 len -= seglen; 378 i++; 379 } 380 ss = &sg->sg_segs[sg->sg_nseg - 1]; 381 for (; len > 0; i++, len -= seglen) { 382 seglen = min(PAGE_SIZE - pgoff, len); 383 paddr = VM_PAGE_TO_PHYS(m[i]) + pgoff; 384 error = _sglist_append_range(sg, &ss, paddr, seglen); 385 if (error) { 386 SGLIST_RESTORE(sg, save); 387 return (error); 388 } 389 pgoff = 0; 390 } 391 return (0); 392 } 393 394 /* 395 * Append the segments that describe a single user address range to a 396 * scatter/gather list. If there are insufficient segments, then this 397 * fails with EFBIG. 398 */ 399 int 400 sglist_append_user(struct sglist *sg, void *buf, size_t len, struct thread *td) 401 { 402 struct sgsave save; 403 int error; 404 405 if (sg->sg_maxseg == 0) 406 return (EINVAL); 407 SGLIST_SAVE(sg, save); 408 error = _sglist_append_buf(sg, buf, len, 409 vmspace_pmap(td->td_proc->p_vmspace), NULL); 410 if (error) 411 SGLIST_RESTORE(sg, save); 412 return (error); 413 } 414 415 /* 416 * Append the segments that describe a single uio to a scatter/gather 417 * list. If there are insufficient segments, then this fails with 418 * EFBIG. 419 */ 420 int 421 sglist_append_uio(struct sglist *sg, struct uio *uio) 422 { 423 struct iovec *iov; 424 struct sgsave save; 425 size_t resid, minlen; 426 pmap_t pmap; 427 int error, i; 428 429 if (sg->sg_maxseg == 0) 430 return (EINVAL); 431 432 resid = uio->uio_resid; 433 iov = uio->uio_iov; 434 435 if (uio->uio_segflg == UIO_USERSPACE) { 436 KASSERT(uio->uio_td != NULL, 437 ("sglist_append_uio: USERSPACE but no thread")); 438 pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace); 439 } else 440 pmap = NULL; 441 442 error = 0; 443 SGLIST_SAVE(sg, save); 444 for (i = 0; i < uio->uio_iovcnt && resid != 0; i++) { 445 /* 446 * Now at the first iovec to load. Load each iovec 447 * until we have exhausted the residual count. 448 */ 449 minlen = MIN(resid, iov[i].iov_len); 450 if (minlen > 0) { 451 error = _sglist_append_buf(sg, iov[i].iov_base, minlen, 452 pmap, NULL); 453 if (error) { 454 SGLIST_RESTORE(sg, save); 455 return (error); 456 } 457 resid -= minlen; 458 } 459 } 460 return (0); 461 } 462 463 /* 464 * Append the segments that describe at most 'resid' bytes from a 465 * single uio to a scatter/gather list. If there are insufficient 466 * segments, then only the amount that fits is appended. 467 */ 468 int 469 sglist_consume_uio(struct sglist *sg, struct uio *uio, size_t resid) 470 { 471 struct iovec *iov; 472 size_t done; 473 pmap_t pmap; 474 int error, len; 475 476 if (sg->sg_maxseg == 0) 477 return (EINVAL); 478 479 if (uio->uio_segflg == UIO_USERSPACE) { 480 KASSERT(uio->uio_td != NULL, 481 ("sglist_consume_uio: USERSPACE but no thread")); 482 pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace); 483 } else 484 pmap = NULL; 485 486 error = 0; 487 while (resid > 0 && uio->uio_resid) { 488 iov = uio->uio_iov; 489 len = iov->iov_len; 490 if (len == 0) { 491 uio->uio_iov++; 492 uio->uio_iovcnt--; 493 continue; 494 } 495 if (len > resid) 496 len = resid; 497 498 /* 499 * Try to append this iovec. If we run out of room, 500 * then break out of the loop. 501 */ 502 error = _sglist_append_buf(sg, iov->iov_base, len, pmap, &done); 503 iov->iov_base = (char *)iov->iov_base + done; 504 iov->iov_len -= done; 505 uio->uio_resid -= done; 506 uio->uio_offset += done; 507 resid -= done; 508 if (error) 509 break; 510 } 511 return (0); 512 } 513 514 /* 515 * Allocate and populate a scatter/gather list to describe a single 516 * kernel virtual address range. 517 */ 518 struct sglist * 519 sglist_build(void *buf, size_t len, int mflags) 520 { 521 struct sglist *sg; 522 int nsegs; 523 524 if (len == 0) 525 return (NULL); 526 527 nsegs = sglist_count(buf, len); 528 sg = sglist_alloc(nsegs, mflags); 529 if (sg == NULL) 530 return (NULL); 531 if (sglist_append(sg, buf, len) != 0) { 532 sglist_free(sg); 533 return (NULL); 534 } 535 return (sg); 536 } 537 538 /* 539 * Clone a new copy of a scatter/gather list. 540 */ 541 struct sglist * 542 sglist_clone(struct sglist *sg, int mflags) 543 { 544 struct sglist *new; 545 546 if (sg == NULL) 547 return (NULL); 548 new = sglist_alloc(sg->sg_maxseg, mflags); 549 if (new == NULL) 550 return (NULL); 551 new->sg_nseg = sg->sg_nseg; 552 bcopy(sg->sg_segs, new->sg_segs, sizeof(struct sglist_seg) * 553 sg->sg_nseg); 554 return (new); 555 } 556 557 /* 558 * Calculate the total length of the segments described in a 559 * scatter/gather list. 560 */ 561 size_t 562 sglist_length(struct sglist *sg) 563 { 564 size_t space; 565 int i; 566 567 space = 0; 568 for (i = 0; i < sg->sg_nseg; i++) 569 space += sg->sg_segs[i].ss_len; 570 return (space); 571 } 572 573 /* 574 * Split a scatter/gather list into two lists. The scatter/gather 575 * entries for the first 'length' bytes of the 'original' list are 576 * stored in the '*head' list and are removed from 'original'. 577 * 578 * If '*head' is NULL, then a new list will be allocated using 579 * 'mflags'. If M_NOWAIT is specified and the allocation fails, 580 * ENOMEM will be returned. 581 * 582 * If '*head' is not NULL, it should point to an empty sglist. If it 583 * does not have enough room for the remaining space, then EFBIG will 584 * be returned. If '*head' is not empty, then EINVAL will be 585 * returned. 586 * 587 * If 'original' is shared (refcount > 1), then EDOOFUS will be 588 * returned. 589 */ 590 int 591 sglist_split(struct sglist *original, struct sglist **head, size_t length, 592 int mflags) 593 { 594 struct sglist *sg; 595 size_t space, split; 596 int count, i; 597 598 if (original->sg_refs > 1) 599 return (EDOOFUS); 600 601 /* Figure out how big of a sglist '*head' has to hold. */ 602 count = 0; 603 space = 0; 604 split = 0; 605 for (i = 0; i < original->sg_nseg; i++) { 606 space += original->sg_segs[i].ss_len; 607 count++; 608 if (space >= length) { 609 /* 610 * If 'length' falls in the middle of a 611 * scatter/gather list entry, then 'split' 612 * holds how much of that entry will remain in 613 * 'original'. 614 */ 615 split = space - length; 616 break; 617 } 618 } 619 620 /* Nothing to do, so leave head empty. */ 621 if (count == 0) 622 return (0); 623 624 if (*head == NULL) { 625 sg = sglist_alloc(count, mflags); 626 if (sg == NULL) 627 return (ENOMEM); 628 *head = sg; 629 } else { 630 sg = *head; 631 if (sg->sg_maxseg < count) 632 return (EFBIG); 633 if (sg->sg_nseg != 0) 634 return (EINVAL); 635 } 636 637 /* Copy 'count' entries to 'sg' from 'original'. */ 638 bcopy(original->sg_segs, sg->sg_segs, count * 639 sizeof(struct sglist_seg)); 640 sg->sg_nseg = count; 641 642 /* 643 * If we had to split a list entry, fixup the last entry in 644 * 'sg' and the new first entry in 'original'. We also 645 * decrement 'count' by 1 since we will only be removing 646 * 'count - 1' segments from 'original' now. 647 */ 648 if (split != 0) { 649 count--; 650 sg->sg_segs[count].ss_len -= split; 651 original->sg_segs[count].ss_paddr = 652 sg->sg_segs[count].ss_paddr + split; 653 original->sg_segs[count].ss_len = split; 654 } 655 656 /* Trim 'count' entries from the front of 'original'. */ 657 original->sg_nseg -= count; 658 bcopy(original->sg_segs + count, original->sg_segs, count * 659 sizeof(struct sglist_seg)); 660 return (0); 661 } 662 663 /* 664 * Append the scatter/gather list elements in 'second' to the 665 * scatter/gather list 'first'. If there is not enough space in 666 * 'first', EFBIG is returned. 667 */ 668 int 669 sglist_join(struct sglist *first, struct sglist *second) 670 { 671 struct sglist_seg *flast, *sfirst; 672 int append; 673 674 /* If 'second' is empty, there is nothing to do. */ 675 if (second->sg_nseg == 0) 676 return (0); 677 678 /* 679 * If the first entry in 'second' can be appended to the last entry 680 * in 'first' then set append to '1'. 681 */ 682 append = 0; 683 flast = &first->sg_segs[first->sg_nseg - 1]; 684 sfirst = &second->sg_segs[0]; 685 if (first->sg_nseg != 0 && 686 flast->ss_paddr + flast->ss_len == sfirst->ss_paddr) 687 append = 1; 688 689 /* Make sure 'first' has enough room. */ 690 if (first->sg_nseg + second->sg_nseg - append > first->sg_maxseg) 691 return (EFBIG); 692 693 /* Merge last in 'first' and first in 'second' if needed. */ 694 if (append) 695 flast->ss_len += sfirst->ss_len; 696 697 /* Append new segments from 'second' to 'first'. */ 698 bcopy(first->sg_segs + first->sg_nseg, second->sg_segs + append, 699 (second->sg_nseg - append) * sizeof(struct sglist_seg)); 700 first->sg_nseg += second->sg_nseg - append; 701 sglist_reset(second); 702 return (0); 703 } 704 705 /* 706 * Generate a new scatter/gather list from a range of an existing 707 * scatter/gather list. The 'offset' and 'length' parameters specify 708 * the logical range of the 'original' list to extract. If that range 709 * is not a subset of the length of 'original', then EINVAL is 710 * returned. The new scatter/gather list is stored in '*slice'. 711 * 712 * If '*slice' is NULL, then a new list will be allocated using 713 * 'mflags'. If M_NOWAIT is specified and the allocation fails, 714 * ENOMEM will be returned. 715 * 716 * If '*slice' is not NULL, it should point to an empty sglist. If it 717 * does not have enough room for the remaining space, then EFBIG will 718 * be returned. If '*slice' is not empty, then EINVAL will be 719 * returned. 720 */ 721 int 722 sglist_slice(struct sglist *original, struct sglist **slice, size_t offset, 723 size_t length, int mflags) 724 { 725 struct sglist *sg; 726 size_t space, end, foffs, loffs; 727 int count, i, fseg; 728 729 /* Nothing to do. */ 730 if (length == 0) 731 return (0); 732 733 /* Figure out how many segments '*slice' needs to have. */ 734 end = offset + length; 735 space = 0; 736 count = 0; 737 fseg = 0; 738 foffs = loffs = 0; 739 for (i = 0; i < original->sg_nseg; i++) { 740 space += original->sg_segs[i].ss_len; 741 if (space > offset) { 742 /* 743 * When we hit the first segment, store its index 744 * in 'fseg' and the offset into the first segment 745 * of 'offset' in 'foffs'. 746 */ 747 if (count == 0) { 748 fseg = i; 749 foffs = offset - (space - 750 original->sg_segs[i].ss_len); 751 CTR1(KTR_DEV, "sglist_slice: foffs = %08lx", 752 foffs); 753 } 754 count++; 755 756 /* 757 * When we hit the last segment, break out of 758 * the loop. Store the amount of extra space 759 * at the end of this segment in 'loffs'. 760 */ 761 if (space >= end) { 762 loffs = space - end; 763 CTR1(KTR_DEV, "sglist_slice: loffs = %08lx", 764 loffs); 765 break; 766 } 767 } 768 } 769 770 /* If we never hit 'end', then 'length' ran off the end, so fail. */ 771 if (space < end) 772 return (EINVAL); 773 774 if (*slice == NULL) { 775 sg = sglist_alloc(count, mflags); 776 if (sg == NULL) 777 return (ENOMEM); 778 *slice = sg; 779 } else { 780 sg = *slice; 781 if (sg->sg_maxseg < count) 782 return (EFBIG); 783 if (sg->sg_nseg != 0) 784 return (EINVAL); 785 } 786 787 /* 788 * Copy over 'count' segments from 'original' starting at 789 * 'fseg' to 'sg'. 790 */ 791 bcopy(original->sg_segs + fseg, sg->sg_segs, 792 count * sizeof(struct sglist_seg)); 793 sg->sg_nseg = count; 794 795 /* Fixup first and last segments if needed. */ 796 if (foffs != 0) { 797 sg->sg_segs[0].ss_paddr += foffs; 798 sg->sg_segs[0].ss_len -= foffs; 799 CTR2(KTR_DEV, "sglist_slice seg[0]: %08lx:%08lx", 800 (long)sg->sg_segs[0].ss_paddr, sg->sg_segs[0].ss_len); 801 } 802 if (loffs != 0) { 803 sg->sg_segs[count - 1].ss_len -= loffs; 804 CTR2(KTR_DEV, "sglist_slice seg[%d]: len %08x", count - 1, 805 sg->sg_segs[count - 1].ss_len); 806 } 807 return (0); 808 } 809