1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 1991, 1992 Linus Torvalds 4 * Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE 5 * Copyright (C) 2016 - 2020 Christoph Hellwig 6 */ 7 #include <linux/init.h> 8 #include <linux/mm.h> 9 #include <linux/blkdev.h> 10 #include <linux/buffer_head.h> 11 #include <linux/mpage.h> 12 #include <linux/uio.h> 13 #include <linux/namei.h> 14 #include <linux/task_io_accounting_ops.h> 15 #include <linux/falloc.h> 16 #include <linux/suspend.h> 17 #include <linux/fs.h> 18 #include <linux/module.h> 19 #include "blk.h" 20 21 static inline struct inode *bdev_file_inode(struct file *file) 22 { 23 return file->f_mapping->host; 24 } 25 26 static int blkdev_get_block(struct inode *inode, sector_t iblock, 27 struct buffer_head *bh, int create) 28 { 29 bh->b_bdev = I_BDEV(inode); 30 bh->b_blocknr = iblock; 31 set_buffer_mapped(bh); 32 return 0; 33 } 34 35 static blk_opf_t dio_bio_write_op(struct kiocb *iocb) 36 { 37 blk_opf_t opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; 38 39 /* avoid the need for a I/O completion work item */ 40 if (iocb_is_dsync(iocb)) 41 opf |= REQ_FUA; 42 return opf; 43 } 44 45 static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos, 46 struct iov_iter *iter) 47 { 48 return pos & (bdev_logical_block_size(bdev) - 1) || 49 !bdev_iter_is_aligned(bdev, iter); 50 } 51 52 #define DIO_INLINE_BIO_VECS 4 53 54 static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb, 55 struct iov_iter *iter, unsigned int nr_pages) 56 { 57 struct block_device *bdev = iocb->ki_filp->private_data; 58 struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs; 59 loff_t pos = iocb->ki_pos; 60 bool should_dirty = false; 61 struct bio bio; 62 ssize_t ret; 63 64 if (blkdev_dio_unaligned(bdev, pos, iter)) 65 return -EINVAL; 66 67 if (nr_pages <= DIO_INLINE_BIO_VECS) 68 vecs = inline_vecs; 69 else { 70 vecs = kmalloc_array(nr_pages, sizeof(struct bio_vec), 71 GFP_KERNEL); 72 if (!vecs) 73 return -ENOMEM; 74 } 75 76 if (iov_iter_rw(iter) == READ) { 77 bio_init(&bio, bdev, vecs, nr_pages, REQ_OP_READ); 78 if (user_backed_iter(iter)) 79 should_dirty = true; 80 } else { 81 bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb)); 82 } 83 bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT; 84 bio.bi_ioprio = iocb->ki_ioprio; 85 86 ret = bio_iov_iter_get_pages(&bio, iter); 87 if (unlikely(ret)) 88 goto out; 89 ret = bio.bi_iter.bi_size; 90 91 if (iov_iter_rw(iter) == WRITE) 92 task_io_account_write(ret); 93 94 if (iocb->ki_flags & IOCB_NOWAIT) 95 bio.bi_opf |= REQ_NOWAIT; 96 97 submit_bio_wait(&bio); 98 99 bio_release_pages(&bio, should_dirty); 100 if (unlikely(bio.bi_status)) 101 ret = blk_status_to_errno(bio.bi_status); 102 103 out: 104 if (vecs != inline_vecs) 105 kfree(vecs); 106 107 bio_uninit(&bio); 108 109 return ret; 110 } 111 112 enum { 113 DIO_SHOULD_DIRTY = 1, 114 DIO_IS_SYNC = 2, 115 }; 116 117 struct blkdev_dio { 118 union { 119 struct kiocb *iocb; 120 struct task_struct *waiter; 121 }; 122 size_t size; 123 atomic_t ref; 124 unsigned int flags; 125 struct bio bio ____cacheline_aligned_in_smp; 126 }; 127 128 static struct bio_set blkdev_dio_pool; 129 130 static void blkdev_bio_end_io(struct bio *bio) 131 { 132 struct blkdev_dio *dio = bio->bi_private; 133 bool should_dirty = dio->flags & DIO_SHOULD_DIRTY; 134 135 if (bio->bi_status && !dio->bio.bi_status) 136 dio->bio.bi_status = bio->bi_status; 137 138 if (atomic_dec_and_test(&dio->ref)) { 139 if (!(dio->flags & DIO_IS_SYNC)) { 140 struct kiocb *iocb = dio->iocb; 141 ssize_t ret; 142 143 WRITE_ONCE(iocb->private, NULL); 144 145 if (likely(!dio->bio.bi_status)) { 146 ret = dio->size; 147 iocb->ki_pos += ret; 148 } else { 149 ret = blk_status_to_errno(dio->bio.bi_status); 150 } 151 152 dio->iocb->ki_complete(iocb, ret); 153 bio_put(&dio->bio); 154 } else { 155 struct task_struct *waiter = dio->waiter; 156 157 WRITE_ONCE(dio->waiter, NULL); 158 blk_wake_io_task(waiter); 159 } 160 } 161 162 if (should_dirty) { 163 bio_check_pages_dirty(bio); 164 } else { 165 bio_release_pages(bio, false); 166 bio_put(bio); 167 } 168 } 169 170 static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, 171 unsigned int nr_pages) 172 { 173 struct block_device *bdev = iocb->ki_filp->private_data; 174 struct blk_plug plug; 175 struct blkdev_dio *dio; 176 struct bio *bio; 177 bool is_read = (iov_iter_rw(iter) == READ), is_sync; 178 blk_opf_t opf = is_read ? REQ_OP_READ : dio_bio_write_op(iocb); 179 loff_t pos = iocb->ki_pos; 180 int ret = 0; 181 182 if (blkdev_dio_unaligned(bdev, pos, iter)) 183 return -EINVAL; 184 185 if (iocb->ki_flags & IOCB_ALLOC_CACHE) 186 opf |= REQ_ALLOC_CACHE; 187 bio = bio_alloc_bioset(bdev, nr_pages, opf, GFP_KERNEL, 188 &blkdev_dio_pool); 189 dio = container_of(bio, struct blkdev_dio, bio); 190 atomic_set(&dio->ref, 1); 191 /* 192 * Grab an extra reference to ensure the dio structure which is embedded 193 * into the first bio stays around. 194 */ 195 bio_get(bio); 196 197 is_sync = is_sync_kiocb(iocb); 198 if (is_sync) { 199 dio->flags = DIO_IS_SYNC; 200 dio->waiter = current; 201 } else { 202 dio->flags = 0; 203 dio->iocb = iocb; 204 } 205 206 dio->size = 0; 207 if (is_read && user_backed_iter(iter)) 208 dio->flags |= DIO_SHOULD_DIRTY; 209 210 blk_start_plug(&plug); 211 212 for (;;) { 213 bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT; 214 bio->bi_private = dio; 215 bio->bi_end_io = blkdev_bio_end_io; 216 bio->bi_ioprio = iocb->ki_ioprio; 217 218 ret = bio_iov_iter_get_pages(bio, iter); 219 if (unlikely(ret)) { 220 bio->bi_status = BLK_STS_IOERR; 221 bio_endio(bio); 222 break; 223 } 224 225 if (is_read) { 226 if (dio->flags & DIO_SHOULD_DIRTY) 227 bio_set_pages_dirty(bio); 228 } else { 229 task_io_account_write(bio->bi_iter.bi_size); 230 } 231 if (iocb->ki_flags & IOCB_NOWAIT) 232 bio->bi_opf |= REQ_NOWAIT; 233 234 dio->size += bio->bi_iter.bi_size; 235 pos += bio->bi_iter.bi_size; 236 237 nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS); 238 if (!nr_pages) { 239 submit_bio(bio); 240 break; 241 } 242 atomic_inc(&dio->ref); 243 submit_bio(bio); 244 bio = bio_alloc(bdev, nr_pages, opf, GFP_KERNEL); 245 } 246 247 blk_finish_plug(&plug); 248 249 if (!is_sync) 250 return -EIOCBQUEUED; 251 252 for (;;) { 253 set_current_state(TASK_UNINTERRUPTIBLE); 254 if (!READ_ONCE(dio->waiter)) 255 break; 256 blk_io_schedule(); 257 } 258 __set_current_state(TASK_RUNNING); 259 260 if (!ret) 261 ret = blk_status_to_errno(dio->bio.bi_status); 262 if (likely(!ret)) 263 ret = dio->size; 264 265 bio_put(&dio->bio); 266 return ret; 267 } 268 269 static void blkdev_bio_end_io_async(struct bio *bio) 270 { 271 struct blkdev_dio *dio = container_of(bio, struct blkdev_dio, bio); 272 struct kiocb *iocb = dio->iocb; 273 ssize_t ret; 274 275 WRITE_ONCE(iocb->private, NULL); 276 277 if (likely(!bio->bi_status)) { 278 ret = dio->size; 279 iocb->ki_pos += ret; 280 } else { 281 ret = blk_status_to_errno(bio->bi_status); 282 } 283 284 iocb->ki_complete(iocb, ret); 285 286 if (dio->flags & DIO_SHOULD_DIRTY) { 287 bio_check_pages_dirty(bio); 288 } else { 289 bio_release_pages(bio, false); 290 bio_put(bio); 291 } 292 } 293 294 static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb, 295 struct iov_iter *iter, 296 unsigned int nr_pages) 297 { 298 struct block_device *bdev = iocb->ki_filp->private_data; 299 bool is_read = iov_iter_rw(iter) == READ; 300 blk_opf_t opf = is_read ? REQ_OP_READ : dio_bio_write_op(iocb); 301 struct blkdev_dio *dio; 302 struct bio *bio; 303 loff_t pos = iocb->ki_pos; 304 int ret = 0; 305 306 if (blkdev_dio_unaligned(bdev, pos, iter)) 307 return -EINVAL; 308 309 if (iocb->ki_flags & IOCB_ALLOC_CACHE) 310 opf |= REQ_ALLOC_CACHE; 311 bio = bio_alloc_bioset(bdev, nr_pages, opf, GFP_KERNEL, 312 &blkdev_dio_pool); 313 dio = container_of(bio, struct blkdev_dio, bio); 314 dio->flags = 0; 315 dio->iocb = iocb; 316 bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT; 317 bio->bi_end_io = blkdev_bio_end_io_async; 318 bio->bi_ioprio = iocb->ki_ioprio; 319 320 if (iov_iter_is_bvec(iter)) { 321 /* 322 * Users don't rely on the iterator being in any particular 323 * state for async I/O returning -EIOCBQUEUED, hence we can 324 * avoid expensive iov_iter_advance(). Bypass 325 * bio_iov_iter_get_pages() and set the bvec directly. 326 */ 327 bio_iov_bvec_set(bio, iter); 328 } else { 329 ret = bio_iov_iter_get_pages(bio, iter); 330 if (unlikely(ret)) { 331 bio_put(bio); 332 return ret; 333 } 334 } 335 dio->size = bio->bi_iter.bi_size; 336 337 if (is_read) { 338 if (user_backed_iter(iter)) { 339 dio->flags |= DIO_SHOULD_DIRTY; 340 bio_set_pages_dirty(bio); 341 } 342 } else { 343 task_io_account_write(bio->bi_iter.bi_size); 344 } 345 346 if (iocb->ki_flags & IOCB_HIPRI) { 347 bio->bi_opf |= REQ_POLLED | REQ_NOWAIT; 348 submit_bio(bio); 349 WRITE_ONCE(iocb->private, bio); 350 } else { 351 if (iocb->ki_flags & IOCB_NOWAIT) 352 bio->bi_opf |= REQ_NOWAIT; 353 submit_bio(bio); 354 } 355 return -EIOCBQUEUED; 356 } 357 358 static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 359 { 360 unsigned int nr_pages; 361 362 if (!iov_iter_count(iter)) 363 return 0; 364 365 nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS + 1); 366 if (likely(nr_pages <= BIO_MAX_VECS)) { 367 if (is_sync_kiocb(iocb)) 368 return __blkdev_direct_IO_simple(iocb, iter, nr_pages); 369 return __blkdev_direct_IO_async(iocb, iter, nr_pages); 370 } 371 return __blkdev_direct_IO(iocb, iter, bio_max_segs(nr_pages)); 372 } 373 374 static int blkdev_writepage(struct page *page, struct writeback_control *wbc) 375 { 376 return block_write_full_page(page, blkdev_get_block, wbc); 377 } 378 379 static int blkdev_read_folio(struct file *file, struct folio *folio) 380 { 381 return block_read_full_folio(folio, blkdev_get_block); 382 } 383 384 static void blkdev_readahead(struct readahead_control *rac) 385 { 386 mpage_readahead(rac, blkdev_get_block); 387 } 388 389 static int blkdev_write_begin(struct file *file, struct address_space *mapping, 390 loff_t pos, unsigned len, struct page **pagep, void **fsdata) 391 { 392 return block_write_begin(mapping, pos, len, pagep, blkdev_get_block); 393 } 394 395 static int blkdev_write_end(struct file *file, struct address_space *mapping, 396 loff_t pos, unsigned len, unsigned copied, struct page *page, 397 void *fsdata) 398 { 399 int ret; 400 ret = block_write_end(file, mapping, pos, len, copied, page, fsdata); 401 402 unlock_page(page); 403 put_page(page); 404 405 return ret; 406 } 407 408 static int blkdev_writepages(struct address_space *mapping, 409 struct writeback_control *wbc) 410 { 411 return generic_writepages(mapping, wbc); 412 } 413 414 const struct address_space_operations def_blk_aops = { 415 .dirty_folio = block_dirty_folio, 416 .invalidate_folio = block_invalidate_folio, 417 .read_folio = blkdev_read_folio, 418 .readahead = blkdev_readahead, 419 .writepage = blkdev_writepage, 420 .write_begin = blkdev_write_begin, 421 .write_end = blkdev_write_end, 422 .writepages = blkdev_writepages, 423 .direct_IO = blkdev_direct_IO, 424 .migrate_folio = buffer_migrate_folio_norefs, 425 .is_dirty_writeback = buffer_check_dirty_writeback, 426 }; 427 428 /* 429 * for a block special file file_inode(file)->i_size is zero 430 * so we compute the size by hand (just as in block_read/write above) 431 */ 432 static loff_t blkdev_llseek(struct file *file, loff_t offset, int whence) 433 { 434 struct inode *bd_inode = bdev_file_inode(file); 435 loff_t retval; 436 437 inode_lock(bd_inode); 438 retval = fixed_size_llseek(file, offset, whence, i_size_read(bd_inode)); 439 inode_unlock(bd_inode); 440 return retval; 441 } 442 443 static int blkdev_fsync(struct file *filp, loff_t start, loff_t end, 444 int datasync) 445 { 446 struct block_device *bdev = filp->private_data; 447 int error; 448 449 error = file_write_and_wait_range(filp, start, end); 450 if (error) 451 return error; 452 453 /* 454 * There is no need to serialise calls to blkdev_issue_flush with 455 * i_mutex and doing so causes performance issues with concurrent 456 * O_SYNC writers to a block device. 457 */ 458 error = blkdev_issue_flush(bdev); 459 if (error == -EOPNOTSUPP) 460 error = 0; 461 462 return error; 463 } 464 465 static int blkdev_open(struct inode *inode, struct file *filp) 466 { 467 struct block_device *bdev; 468 469 /* 470 * Preserve backwards compatibility and allow large file access 471 * even if userspace doesn't ask for it explicitly. Some mkfs 472 * binary needs it. We might want to drop this workaround 473 * during an unstable branch. 474 */ 475 filp->f_flags |= O_LARGEFILE; 476 filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC; 477 478 if (filp->f_flags & O_NDELAY) 479 filp->f_mode |= FMODE_NDELAY; 480 if (filp->f_flags & O_EXCL) 481 filp->f_mode |= FMODE_EXCL; 482 if ((filp->f_flags & O_ACCMODE) == 3) 483 filp->f_mode |= FMODE_WRITE_IOCTL; 484 485 bdev = blkdev_get_by_dev(inode->i_rdev, filp->f_mode, filp); 486 if (IS_ERR(bdev)) 487 return PTR_ERR(bdev); 488 489 filp->private_data = bdev; 490 filp->f_mapping = bdev->bd_inode->i_mapping; 491 filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping); 492 return 0; 493 } 494 495 static int blkdev_close(struct inode *inode, struct file *filp) 496 { 497 struct block_device *bdev = filp->private_data; 498 499 blkdev_put(bdev, filp->f_mode); 500 return 0; 501 } 502 503 /* 504 * Write data to the block device. Only intended for the block device itself 505 * and the raw driver which basically is a fake block device. 506 * 507 * Does not take i_mutex for the write and thus is not for general purpose 508 * use. 509 */ 510 static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from) 511 { 512 struct block_device *bdev = iocb->ki_filp->private_data; 513 struct inode *bd_inode = bdev->bd_inode; 514 loff_t size = bdev_nr_bytes(bdev); 515 struct blk_plug plug; 516 size_t shorted = 0; 517 ssize_t ret; 518 519 if (bdev_read_only(bdev)) 520 return -EPERM; 521 522 if (IS_SWAPFILE(bd_inode) && !is_hibernate_resume_dev(bd_inode->i_rdev)) 523 return -ETXTBSY; 524 525 if (!iov_iter_count(from)) 526 return 0; 527 528 if (iocb->ki_pos >= size) 529 return -ENOSPC; 530 531 if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT) 532 return -EOPNOTSUPP; 533 534 size -= iocb->ki_pos; 535 if (iov_iter_count(from) > size) { 536 shorted = iov_iter_count(from) - size; 537 iov_iter_truncate(from, size); 538 } 539 540 blk_start_plug(&plug); 541 ret = __generic_file_write_iter(iocb, from); 542 if (ret > 0) 543 ret = generic_write_sync(iocb, ret); 544 iov_iter_reexpand(from, iov_iter_count(from) + shorted); 545 blk_finish_plug(&plug); 546 return ret; 547 } 548 549 static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) 550 { 551 struct block_device *bdev = iocb->ki_filp->private_data; 552 loff_t size = bdev_nr_bytes(bdev); 553 loff_t pos = iocb->ki_pos; 554 size_t shorted = 0; 555 ssize_t ret = 0; 556 size_t count; 557 558 if (unlikely(pos + iov_iter_count(to) > size)) { 559 if (pos >= size) 560 return 0; 561 size -= pos; 562 shorted = iov_iter_count(to) - size; 563 iov_iter_truncate(to, size); 564 } 565 566 count = iov_iter_count(to); 567 if (!count) 568 goto reexpand; /* skip atime */ 569 570 if (iocb->ki_flags & IOCB_DIRECT) { 571 struct address_space *mapping = iocb->ki_filp->f_mapping; 572 573 if (iocb->ki_flags & IOCB_NOWAIT) { 574 if (filemap_range_needs_writeback(mapping, pos, 575 pos + count - 1)) { 576 ret = -EAGAIN; 577 goto reexpand; 578 } 579 } else { 580 ret = filemap_write_and_wait_range(mapping, pos, 581 pos + count - 1); 582 if (ret < 0) 583 goto reexpand; 584 } 585 586 file_accessed(iocb->ki_filp); 587 588 ret = blkdev_direct_IO(iocb, to); 589 if (ret >= 0) { 590 iocb->ki_pos += ret; 591 count -= ret; 592 } 593 iov_iter_revert(to, count - iov_iter_count(to)); 594 if (ret < 0 || !count) 595 goto reexpand; 596 } 597 598 ret = filemap_read(iocb, to, ret); 599 600 reexpand: 601 if (unlikely(shorted)) 602 iov_iter_reexpand(to, iov_iter_count(to) + shorted); 603 return ret; 604 } 605 606 #define BLKDEV_FALLOC_FL_SUPPORTED \ 607 (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \ 608 FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE) 609 610 static long blkdev_fallocate(struct file *file, int mode, loff_t start, 611 loff_t len) 612 { 613 struct inode *inode = bdev_file_inode(file); 614 struct block_device *bdev = I_BDEV(inode); 615 loff_t end = start + len - 1; 616 loff_t isize; 617 int error; 618 619 /* Fail if we don't recognize the flags. */ 620 if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED) 621 return -EOPNOTSUPP; 622 623 /* Don't go off the end of the device. */ 624 isize = bdev_nr_bytes(bdev); 625 if (start >= isize) 626 return -EINVAL; 627 if (end >= isize) { 628 if (mode & FALLOC_FL_KEEP_SIZE) { 629 len = isize - start; 630 end = start + len - 1; 631 } else 632 return -EINVAL; 633 } 634 635 /* 636 * Don't allow IO that isn't aligned to logical block size. 637 */ 638 if ((start | len) & (bdev_logical_block_size(bdev) - 1)) 639 return -EINVAL; 640 641 filemap_invalidate_lock(inode->i_mapping); 642 643 /* Invalidate the page cache, including dirty pages. */ 644 error = truncate_bdev_range(bdev, file->f_mode, start, end); 645 if (error) 646 goto fail; 647 648 switch (mode) { 649 case FALLOC_FL_ZERO_RANGE: 650 case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE: 651 error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT, 652 len >> SECTOR_SHIFT, GFP_KERNEL, 653 BLKDEV_ZERO_NOUNMAP); 654 break; 655 case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE: 656 error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT, 657 len >> SECTOR_SHIFT, GFP_KERNEL, 658 BLKDEV_ZERO_NOFALLBACK); 659 break; 660 case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE: 661 error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT, 662 len >> SECTOR_SHIFT, GFP_KERNEL); 663 break; 664 default: 665 error = -EOPNOTSUPP; 666 } 667 668 fail: 669 filemap_invalidate_unlock(inode->i_mapping); 670 return error; 671 } 672 673 const struct file_operations def_blk_fops = { 674 .open = blkdev_open, 675 .release = blkdev_close, 676 .llseek = blkdev_llseek, 677 .read_iter = blkdev_read_iter, 678 .write_iter = blkdev_write_iter, 679 .iopoll = iocb_bio_iopoll, 680 .mmap = generic_file_mmap, 681 .fsync = blkdev_fsync, 682 .unlocked_ioctl = blkdev_ioctl, 683 #ifdef CONFIG_COMPAT 684 .compat_ioctl = compat_blkdev_ioctl, 685 #endif 686 .splice_read = generic_file_splice_read, 687 .splice_write = iter_file_splice_write, 688 .fallocate = blkdev_fallocate, 689 }; 690 691 static __init int blkdev_init(void) 692 { 693 return bioset_init(&blkdev_dio_pool, 4, 694 offsetof(struct blkdev_dio, bio), 695 BIOSET_NEED_BVECS|BIOSET_PERCPU_CACHE); 696 } 697 module_init(blkdev_init); 698