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 * Allocate a scatter/gather list along with 'nsegs' segments. The 196 * 'mflags' parameters are the same as passed to malloc(9). The caller 197 * should use sglist_free() to free this list. 198 */ 199 struct sglist * 200 sglist_alloc(int nsegs, int mflags) 201 { 202 struct sglist *sg; 203 204 sg = malloc(sizeof(struct sglist) + nsegs * sizeof(struct sglist_seg), 205 M_SGLIST, mflags); 206 if (sg == NULL) 207 return (NULL); 208 sglist_init(sg, nsegs, (struct sglist_seg *)(sg + 1)); 209 return (sg); 210 } 211 212 /* 213 * Free a scatter/gather list allocated via sglist_allc(). 214 */ 215 void 216 sglist_free(struct sglist *sg) 217 { 218 219 if (sg == NULL) 220 return; 221 222 if (refcount_release(&sg->sg_refs)) 223 free(sg, M_SGLIST); 224 } 225 226 /* 227 * Append the segments to describe a single kernel virtual address 228 * range to a scatter/gather list. If there are insufficient 229 * segments, then this fails with EFBIG. 230 */ 231 int 232 sglist_append(struct sglist *sg, void *buf, size_t len) 233 { 234 struct sgsave save; 235 int error; 236 237 if (sg->sg_maxseg == 0) 238 return (EINVAL); 239 SGLIST_SAVE(sg, save); 240 error = _sglist_append_buf(sg, buf, len, NULL, NULL); 241 if (error) 242 SGLIST_RESTORE(sg, save); 243 return (error); 244 } 245 246 /* 247 * Append the segments to describe a bio's data to a scatter/gather list. 248 * If there are insufficient segments, then this fails with EFBIG. 249 * 250 * NOTE: This function expects bio_bcount to be initialized. 251 */ 252 int 253 sglist_append_bio(struct sglist *sg, struct bio *bp) 254 { 255 struct sgsave save; 256 vm_paddr_t paddr; 257 size_t len, tlen; 258 int error, i, ma_offs; 259 260 if ((bp->bio_flags & BIO_UNMAPPED) == 0) { 261 error = sglist_append(sg, bp->bio_data, bp->bio_bcount); 262 return (error); 263 } 264 265 if (sg->sg_maxseg == 0) 266 return (EINVAL); 267 268 SGLIST_SAVE(sg, save); 269 tlen = bp->bio_bcount; 270 ma_offs = bp->bio_ma_offset; 271 for (i = 0; tlen > 0; i++, tlen -= len) { 272 len = min(PAGE_SIZE - ma_offs, tlen); 273 paddr = VM_PAGE_TO_PHYS(bp->bio_ma[i]) + ma_offs; 274 error = sglist_append_phys(sg, paddr, len); 275 if (error) { 276 SGLIST_RESTORE(sg, save); 277 return (error); 278 } 279 ma_offs = 0; 280 } 281 return (0); 282 } 283 284 /* 285 * Append a single physical address range to a scatter/gather list. 286 * If there are insufficient segments, then this fails with EFBIG. 287 */ 288 int 289 sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len) 290 { 291 struct sglist_seg *ss; 292 struct sgsave save; 293 int error; 294 295 if (sg->sg_maxseg == 0) 296 return (EINVAL); 297 if (len == 0) 298 return (0); 299 300 if (sg->sg_nseg == 0) { 301 sg->sg_segs[0].ss_paddr = paddr; 302 sg->sg_segs[0].ss_len = len; 303 sg->sg_nseg = 1; 304 return (0); 305 } 306 ss = &sg->sg_segs[sg->sg_nseg - 1]; 307 SGLIST_SAVE(sg, save); 308 error = _sglist_append_range(sg, &ss, paddr, len); 309 if (error) 310 SGLIST_RESTORE(sg, save); 311 return (error); 312 } 313 314 /* 315 * Append the segments that describe a single mbuf chain to a 316 * scatter/gather list. If there are insufficient segments, then this 317 * fails with EFBIG. 318 */ 319 int 320 sglist_append_mbuf(struct sglist *sg, struct mbuf *m0) 321 { 322 struct sgsave save; 323 struct mbuf *m; 324 int error; 325 326 if (sg->sg_maxseg == 0) 327 return (EINVAL); 328 329 error = 0; 330 SGLIST_SAVE(sg, save); 331 for (m = m0; m != NULL; m = m->m_next) { 332 if (m->m_len > 0) { 333 error = sglist_append(sg, m->m_data, m->m_len); 334 if (error) { 335 SGLIST_RESTORE(sg, save); 336 return (error); 337 } 338 } 339 } 340 return (0); 341 } 342 343 /* 344 * Append the segments that describe a single user address range to a 345 * scatter/gather list. If there are insufficient segments, then this 346 * fails with EFBIG. 347 */ 348 int 349 sglist_append_user(struct sglist *sg, void *buf, size_t len, struct thread *td) 350 { 351 struct sgsave save; 352 int error; 353 354 if (sg->sg_maxseg == 0) 355 return (EINVAL); 356 SGLIST_SAVE(sg, save); 357 error = _sglist_append_buf(sg, buf, len, 358 vmspace_pmap(td->td_proc->p_vmspace), NULL); 359 if (error) 360 SGLIST_RESTORE(sg, save); 361 return (error); 362 } 363 364 /* 365 * Append the segments that describe a single uio to a scatter/gather 366 * list. If there are insufficient segments, then this fails with 367 * EFBIG. 368 */ 369 int 370 sglist_append_uio(struct sglist *sg, struct uio *uio) 371 { 372 struct iovec *iov; 373 struct sgsave save; 374 size_t resid, minlen; 375 pmap_t pmap; 376 int error, i; 377 378 if (sg->sg_maxseg == 0) 379 return (EINVAL); 380 381 resid = uio->uio_resid; 382 iov = uio->uio_iov; 383 384 if (uio->uio_segflg == UIO_USERSPACE) { 385 KASSERT(uio->uio_td != NULL, 386 ("sglist_append_uio: USERSPACE but no thread")); 387 pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace); 388 } else 389 pmap = NULL; 390 391 error = 0; 392 SGLIST_SAVE(sg, save); 393 for (i = 0; i < uio->uio_iovcnt && resid != 0; i++) { 394 /* 395 * Now at the first iovec to load. Load each iovec 396 * until we have exhausted the residual count. 397 */ 398 minlen = MIN(resid, iov[i].iov_len); 399 if (minlen > 0) { 400 error = _sglist_append_buf(sg, iov[i].iov_base, minlen, 401 pmap, NULL); 402 if (error) { 403 SGLIST_RESTORE(sg, save); 404 return (error); 405 } 406 resid -= minlen; 407 } 408 } 409 return (0); 410 } 411 412 /* 413 * Append the segments that describe at most 'resid' bytes from a 414 * single uio to a scatter/gather list. If there are insufficient 415 * segments, then only the amount that fits is appended. 416 */ 417 int 418 sglist_consume_uio(struct sglist *sg, struct uio *uio, size_t resid) 419 { 420 struct iovec *iov; 421 size_t done; 422 pmap_t pmap; 423 int error, len; 424 425 if (sg->sg_maxseg == 0) 426 return (EINVAL); 427 428 if (uio->uio_segflg == UIO_USERSPACE) { 429 KASSERT(uio->uio_td != NULL, 430 ("sglist_consume_uio: USERSPACE but no thread")); 431 pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace); 432 } else 433 pmap = NULL; 434 435 error = 0; 436 while (resid > 0 && uio->uio_resid) { 437 iov = uio->uio_iov; 438 len = iov->iov_len; 439 if (len == 0) { 440 uio->uio_iov++; 441 uio->uio_iovcnt--; 442 continue; 443 } 444 if (len > resid) 445 len = resid; 446 447 /* 448 * Try to append this iovec. If we run out of room, 449 * then break out of the loop. 450 */ 451 error = _sglist_append_buf(sg, iov->iov_base, len, pmap, &done); 452 iov->iov_base = (char *)iov->iov_base + done; 453 iov->iov_len -= done; 454 uio->uio_resid -= done; 455 uio->uio_offset += done; 456 resid -= done; 457 if (error) 458 break; 459 } 460 return (0); 461 } 462 463 /* 464 * Allocate and populate a scatter/gather list to describe a single 465 * kernel virtual address range. 466 */ 467 struct sglist * 468 sglist_build(void *buf, size_t len, int mflags) 469 { 470 struct sglist *sg; 471 int nsegs; 472 473 if (len == 0) 474 return (NULL); 475 476 nsegs = sglist_count(buf, len); 477 sg = sglist_alloc(nsegs, mflags); 478 if (sg == NULL) 479 return (NULL); 480 if (sglist_append(sg, buf, len) != 0) { 481 sglist_free(sg); 482 return (NULL); 483 } 484 return (sg); 485 } 486 487 /* 488 * Clone a new copy of a scatter/gather list. 489 */ 490 struct sglist * 491 sglist_clone(struct sglist *sg, int mflags) 492 { 493 struct sglist *new; 494 495 if (sg == NULL) 496 return (NULL); 497 new = sglist_alloc(sg->sg_maxseg, mflags); 498 if (new == NULL) 499 return (NULL); 500 new->sg_nseg = sg->sg_nseg; 501 bcopy(sg->sg_segs, new->sg_segs, sizeof(struct sglist_seg) * 502 sg->sg_nseg); 503 return (new); 504 } 505 506 /* 507 * Calculate the total length of the segments described in a 508 * scatter/gather list. 509 */ 510 size_t 511 sglist_length(struct sglist *sg) 512 { 513 size_t space; 514 int i; 515 516 space = 0; 517 for (i = 0; i < sg->sg_nseg; i++) 518 space += sg->sg_segs[i].ss_len; 519 return (space); 520 } 521 522 /* 523 * Split a scatter/gather list into two lists. The scatter/gather 524 * entries for the first 'length' bytes of the 'original' list are 525 * stored in the '*head' list and are removed from 'original'. 526 * 527 * If '*head' is NULL, then a new list will be allocated using 528 * 'mflags'. If M_NOWAIT is specified and the allocation fails, 529 * ENOMEM will be returned. 530 * 531 * If '*head' is not NULL, it should point to an empty sglist. If it 532 * does not have enough room for the remaining space, then EFBIG will 533 * be returned. If '*head' is not empty, then EINVAL will be 534 * returned. 535 * 536 * If 'original' is shared (refcount > 1), then EDOOFUS will be 537 * returned. 538 */ 539 int 540 sglist_split(struct sglist *original, struct sglist **head, size_t length, 541 int mflags) 542 { 543 struct sglist *sg; 544 size_t space, split; 545 int count, i; 546 547 if (original->sg_refs > 1) 548 return (EDOOFUS); 549 550 /* Figure out how big of a sglist '*head' has to hold. */ 551 count = 0; 552 space = 0; 553 split = 0; 554 for (i = 0; i < original->sg_nseg; i++) { 555 space += original->sg_segs[i].ss_len; 556 count++; 557 if (space >= length) { 558 /* 559 * If 'length' falls in the middle of a 560 * scatter/gather list entry, then 'split' 561 * holds how much of that entry will remain in 562 * 'original'. 563 */ 564 split = space - length; 565 break; 566 } 567 } 568 569 /* Nothing to do, so leave head empty. */ 570 if (count == 0) 571 return (0); 572 573 if (*head == NULL) { 574 sg = sglist_alloc(count, mflags); 575 if (sg == NULL) 576 return (ENOMEM); 577 *head = sg; 578 } else { 579 sg = *head; 580 if (sg->sg_maxseg < count) 581 return (EFBIG); 582 if (sg->sg_nseg != 0) 583 return (EINVAL); 584 } 585 586 /* Copy 'count' entries to 'sg' from 'original'. */ 587 bcopy(original->sg_segs, sg->sg_segs, count * 588 sizeof(struct sglist_seg)); 589 sg->sg_nseg = count; 590 591 /* 592 * If we had to split a list entry, fixup the last entry in 593 * 'sg' and the new first entry in 'original'. We also 594 * decrement 'count' by 1 since we will only be removing 595 * 'count - 1' segments from 'original' now. 596 */ 597 if (split != 0) { 598 count--; 599 sg->sg_segs[count].ss_len -= split; 600 original->sg_segs[count].ss_paddr = 601 sg->sg_segs[count].ss_paddr + split; 602 original->sg_segs[count].ss_len = split; 603 } 604 605 /* Trim 'count' entries from the front of 'original'. */ 606 original->sg_nseg -= count; 607 bcopy(original->sg_segs + count, original->sg_segs, count * 608 sizeof(struct sglist_seg)); 609 return (0); 610 } 611 612 /* 613 * Append the scatter/gather list elements in 'second' to the 614 * scatter/gather list 'first'. If there is not enough space in 615 * 'first', EFBIG is returned. 616 */ 617 int 618 sglist_join(struct sglist *first, struct sglist *second) 619 { 620 struct sglist_seg *flast, *sfirst; 621 int append; 622 623 /* If 'second' is empty, there is nothing to do. */ 624 if (second->sg_nseg == 0) 625 return (0); 626 627 /* 628 * If the first entry in 'second' can be appended to the last entry 629 * in 'first' then set append to '1'. 630 */ 631 append = 0; 632 flast = &first->sg_segs[first->sg_nseg - 1]; 633 sfirst = &second->sg_segs[0]; 634 if (first->sg_nseg != 0 && 635 flast->ss_paddr + flast->ss_len == sfirst->ss_paddr) 636 append = 1; 637 638 /* Make sure 'first' has enough room. */ 639 if (first->sg_nseg + second->sg_nseg - append > first->sg_maxseg) 640 return (EFBIG); 641 642 /* Merge last in 'first' and first in 'second' if needed. */ 643 if (append) 644 flast->ss_len += sfirst->ss_len; 645 646 /* Append new segments from 'second' to 'first'. */ 647 bcopy(first->sg_segs + first->sg_nseg, second->sg_segs + append, 648 (second->sg_nseg - append) * sizeof(struct sglist_seg)); 649 first->sg_nseg += second->sg_nseg - append; 650 sglist_reset(second); 651 return (0); 652 } 653 654 /* 655 * Generate a new scatter/gather list from a range of an existing 656 * scatter/gather list. The 'offset' and 'length' parameters specify 657 * the logical range of the 'original' list to extract. If that range 658 * is not a subset of the length of 'original', then EINVAL is 659 * returned. The new scatter/gather list is stored in '*slice'. 660 * 661 * If '*slice' is NULL, then a new list will be allocated using 662 * 'mflags'. If M_NOWAIT is specified and the allocation fails, 663 * ENOMEM will be returned. 664 * 665 * If '*slice' is not NULL, it should point to an empty sglist. If it 666 * does not have enough room for the remaining space, then EFBIG will 667 * be returned. If '*slice' is not empty, then EINVAL will be 668 * returned. 669 */ 670 int 671 sglist_slice(struct sglist *original, struct sglist **slice, size_t offset, 672 size_t length, int mflags) 673 { 674 struct sglist *sg; 675 size_t space, end, foffs, loffs; 676 int count, i, fseg; 677 678 /* Nothing to do. */ 679 if (length == 0) 680 return (0); 681 682 /* Figure out how many segments '*slice' needs to have. */ 683 end = offset + length; 684 space = 0; 685 count = 0; 686 fseg = 0; 687 foffs = loffs = 0; 688 for (i = 0; i < original->sg_nseg; i++) { 689 space += original->sg_segs[i].ss_len; 690 if (space > offset) { 691 /* 692 * When we hit the first segment, store its index 693 * in 'fseg' and the offset into the first segment 694 * of 'offset' in 'foffs'. 695 */ 696 if (count == 0) { 697 fseg = i; 698 foffs = offset - (space - 699 original->sg_segs[i].ss_len); 700 CTR1(KTR_DEV, "sglist_slice: foffs = %08lx", 701 foffs); 702 } 703 count++; 704 705 /* 706 * When we hit the last segment, break out of 707 * the loop. Store the amount of extra space 708 * at the end of this segment in 'loffs'. 709 */ 710 if (space >= end) { 711 loffs = space - end; 712 CTR1(KTR_DEV, "sglist_slice: loffs = %08lx", 713 loffs); 714 break; 715 } 716 } 717 } 718 719 /* If we never hit 'end', then 'length' ran off the end, so fail. */ 720 if (space < end) 721 return (EINVAL); 722 723 if (*slice == NULL) { 724 sg = sglist_alloc(count, mflags); 725 if (sg == NULL) 726 return (ENOMEM); 727 *slice = sg; 728 } else { 729 sg = *slice; 730 if (sg->sg_maxseg < count) 731 return (EFBIG); 732 if (sg->sg_nseg != 0) 733 return (EINVAL); 734 } 735 736 /* 737 * Copy over 'count' segments from 'original' starting at 738 * 'fseg' to 'sg'. 739 */ 740 bcopy(original->sg_segs + fseg, sg->sg_segs, 741 count * sizeof(struct sglist_seg)); 742 sg->sg_nseg = count; 743 744 /* Fixup first and last segments if needed. */ 745 if (foffs != 0) { 746 sg->sg_segs[0].ss_paddr += foffs; 747 sg->sg_segs[0].ss_len -= foffs; 748 CTR2(KTR_DEV, "sglist_slice seg[0]: %08lx:%08lx", 749 (long)sg->sg_segs[0].ss_paddr, sg->sg_segs[0].ss_len); 750 } 751 if (loffs != 0) { 752 sg->sg_segs[count - 1].ss_len -= loffs; 753 CTR2(KTR_DEV, "sglist_slice seg[%d]: len %08x", count - 1, 754 sg->sg_segs[count - 1].ss_len); 755 } 756 return (0); 757 } 758