1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * fs/direct-io.c 4 * 5 * Copyright (C) 2002, Linus Torvalds. 6 * 7 * O_DIRECT 8 * 9 * 04Jul2002 Andrew Morton 10 * Initial version 11 * 11Sep2002 janetinc@us.ibm.com 12 * added readv/writev support. 13 * 29Oct2002 Andrew Morton 14 * rewrote bio_add_page() support. 15 * 30Oct2002 pbadari@us.ibm.com 16 * added support for non-aligned IO. 17 * 06Nov2002 pbadari@us.ibm.com 18 * added asynchronous IO support. 19 * 21Jul2003 nathans@sgi.com 20 * added IO completion notifier. 21 */ 22 23#include <linux/kernel.h> 24#include <linux/module.h> 25#include <linux/types.h> 26#include <linux/fs.h> 27#include <linux/mm.h> 28#include <linux/slab.h> 29#include <linux/highmem.h> 30#include <linux/pagemap.h> 31#include <linux/task_io_accounting_ops.h> 32#include <linux/bio.h> 33#include <linux/wait.h> 34#include <linux/err.h> 35#include <linux/blkdev.h> 36#include <linux/buffer_head.h> 37#include <linux/rwsem.h> 38#include <linux/uio.h> 39#include <linux/atomic.h> 40#include <linux/prefetch.h> 41 42#include "internal.h" 43 44/* 45 * How many user pages to map in one call to iov_iter_extract_pages(). This 46 * determines the size of a structure in the slab cache 47 */ 48#define DIO_PAGES 64 49 50/* 51 * Flags for dio_complete() 52 */ 53#define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */ 54#define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */ 55 56/* 57 * This code generally works in units of "dio_blocks". A dio_block is 58 * somewhere between the hard sector size and the filesystem block size. it 59 * is determined on a per-invocation basis. When talking to the filesystem 60 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity 61 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted 62 * to bio_block quantities by shifting left by blkfactor. 63 * 64 * If blkfactor is zero then the user's request was aligned to the filesystem's 65 * blocksize. 66 */ 67 68/* dio_state only used in the submission path */ 69 70struct dio_submit { 71 struct bio *bio; /* bio under assembly */ 72 unsigned blkbits; /* doesn't change */ 73 unsigned blkfactor; /* When we're using an alignment which 74 is finer than the filesystem's soft 75 blocksize, this specifies how much 76 finer. blkfactor=2 means 1/4-block 77 alignment. Does not change */ 78 unsigned start_zero_done; /* flag: sub-blocksize zeroing has 79 been performed at the start of a 80 write */ 81 int pages_in_io; /* approximate total IO pages */ 82 sector_t block_in_file; /* Current offset into the underlying 83 file in dio_block units. */ 84 unsigned blocks_available; /* At block_in_file. changes */ 85 int reap_counter; /* rate limit reaping */ 86 sector_t final_block_in_request;/* doesn't change */ 87 int boundary; /* prev block is at a boundary */ 88 get_block_t *get_block; /* block mapping function */ 89 90 loff_t logical_offset_in_bio; /* current first logical block in bio */ 91 sector_t final_block_in_bio; /* current final block in bio + 1 */ 92 sector_t next_block_for_io; /* next block to be put under IO, 93 in dio_blocks units */ 94 95 /* 96 * Deferred addition of a page to the dio. These variables are 97 * private to dio_send_cur_page(), submit_page_section() and 98 * dio_bio_add_page(). 99 */ 100 struct page *cur_page; /* The page */ 101 unsigned cur_page_offset; /* Offset into it, in bytes */ 102 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ 103 sector_t cur_page_block; /* Where it starts */ 104 loff_t cur_page_fs_offset; /* Offset in file */ 105 106 struct iov_iter *iter; 107 /* 108 * Page queue. These variables belong to dio_refill_pages() and 109 * dio_get_page(). 110 */ 111 unsigned head; /* next page to process */ 112 unsigned tail; /* last valid page + 1 */ 113 size_t from, to; 114}; 115 116/* dio_state communicated between submission path and end_io */ 117struct dio { 118 int flags; /* doesn't change */ 119 blk_opf_t opf; /* request operation type and flags */ 120 struct gendisk *bio_disk; 121 struct inode *inode; 122 loff_t i_size; /* i_size when submitted */ 123 dio_iodone_t *end_io; /* IO completion function */ 124 bool is_pinned; /* T if we have pins on the pages */ 125 126 void *private; /* copy from map_bh.b_private */ 127 128 /* BIO completion state */ 129 spinlock_t bio_lock; /* protects BIO fields below */ 130 int page_errors; /* err from iov_iter_extract_pages() */ 131 int is_async; /* is IO async ? */ 132 bool defer_completion; /* defer AIO completion to workqueue? */ 133 bool should_dirty; /* if pages should be dirtied */ 134 int io_error; /* IO error in completion path */ 135 unsigned long refcount; /* direct_io_worker() and bios */ 136 struct bio *bio_list; /* singly linked via bi_private */ 137 struct task_struct *waiter; /* waiting task (NULL if none) */ 138 139 /* AIO related stuff */ 140 struct kiocb *iocb; /* kiocb */ 141 ssize_t result; /* IO result */ 142 143 /* 144 * pages[] (and any fields placed after it) are not zeroed out at 145 * allocation time. Don't add new fields after pages[] unless you 146 * wish that they not be zeroed. 147 */ 148 union { 149 struct page *pages[DIO_PAGES]; /* page buffer */ 150 struct work_struct complete_work;/* deferred AIO completion */ 151 }; 152} ____cacheline_aligned_in_smp; 153 154static struct kmem_cache *dio_cache __read_mostly; 155 156/* 157 * How many pages are in the queue? 158 */ 159static inline unsigned dio_pages_present(struct dio_submit *sdio) 160{ 161 return sdio->tail - sdio->head; 162} 163 164/* 165 * Go grab and pin some userspace pages. Typically we'll get 64 at a time. 166 */ 167static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) 168{ 169 struct page **pages = dio->pages; 170 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 171 ssize_t ret; 172 173 ret = iov_iter_extract_pages(sdio->iter, &pages, LONG_MAX, 174 DIO_PAGES, 0, &sdio->from); 175 176 if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) { 177 /* 178 * A memory fault, but the filesystem has some outstanding 179 * mapped blocks. We need to use those blocks up to avoid 180 * leaking stale data in the file. 181 */ 182 if (dio->page_errors == 0) 183 dio->page_errors = ret; 184 dio->pages[0] = ZERO_PAGE(0); 185 sdio->head = 0; 186 sdio->tail = 1; 187 sdio->from = 0; 188 sdio->to = PAGE_SIZE; 189 return 0; 190 } 191 192 if (ret >= 0) { 193 ret += sdio->from; 194 sdio->head = 0; 195 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE; 196 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1; 197 return 0; 198 } 199 return ret; 200} 201 202/* 203 * Get another userspace page. Returns an ERR_PTR on error. Pages are 204 * buffered inside the dio so that we can call iov_iter_extract_pages() 205 * against a decent number of pages, less frequently. To provide nicer use of 206 * the L1 cache. 207 */ 208static inline struct page *dio_get_page(struct dio *dio, 209 struct dio_submit *sdio) 210{ 211 if (dio_pages_present(sdio) == 0) { 212 int ret; 213 214 ret = dio_refill_pages(dio, sdio); 215 if (ret) 216 return ERR_PTR(ret); 217 BUG_ON(dio_pages_present(sdio) == 0); 218 } 219 return dio->pages[sdio->head]; 220} 221 222static void dio_pin_page(struct dio *dio, struct page *page) 223{ 224 if (dio->is_pinned) 225 folio_add_pin(page_folio(page)); 226} 227 228static void dio_unpin_page(struct dio *dio, struct page *page) 229{ 230 if (dio->is_pinned) 231 unpin_user_page(page); 232} 233 234/* 235 * dio_complete() - called when all DIO BIO I/O has been completed 236 * 237 * This drops i_dio_count, lets interested parties know that a DIO operation 238 * has completed, and calculates the resulting return code for the operation. 239 * 240 * It lets the filesystem know if it registered an interest earlier via 241 * get_block. Pass the private field of the map buffer_head so that 242 * filesystems can use it to hold additional state between get_block calls and 243 * dio_complete. 244 */ 245static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags) 246{ 247 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 248 loff_t offset = dio->iocb->ki_pos; 249 ssize_t transferred = 0; 250 int err; 251 252 /* 253 * AIO submission can race with bio completion to get here while 254 * expecting to have the last io completed by bio completion. 255 * In that case -EIOCBQUEUED is in fact not an error we want 256 * to preserve through this call. 257 */ 258 if (ret == -EIOCBQUEUED) 259 ret = 0; 260 261 if (dio->result) { 262 transferred = dio->result; 263 264 /* Check for short read case */ 265 if (dio_op == REQ_OP_READ && 266 ((offset + transferred) > dio->i_size)) 267 transferred = dio->i_size - offset; 268 /* ignore EFAULT if some IO has been done */ 269 if (unlikely(ret == -EFAULT) && transferred) 270 ret = 0; 271 } 272 273 if (ret == 0) 274 ret = dio->page_errors; 275 if (ret == 0) 276 ret = dio->io_error; 277 if (ret == 0) 278 ret = transferred; 279 280 if (dio->end_io) { 281 // XXX: ki_pos?? 282 err = dio->end_io(dio->iocb, offset, ret, dio->private); 283 if (err) 284 ret = err; 285 } 286 287 /* 288 * Try again to invalidate clean pages which might have been cached by 289 * non-direct readahead, or faulted in by get_user_pages() if the source 290 * of the write was an mmap'ed region of the file we're writing. Either 291 * one is a pretty crazy thing to do, so we don't support it 100%. If 292 * this invalidation fails, tough, the write still worked... 293 * 294 * And this page cache invalidation has to be after dio->end_io(), as 295 * some filesystems convert unwritten extents to real allocations in 296 * end_io() when necessary, otherwise a racing buffer read would cache 297 * zeros from unwritten extents. 298 */ 299 if (flags & DIO_COMPLETE_INVALIDATE && 300 ret > 0 && dio_op == REQ_OP_WRITE) 301 kiocb_invalidate_post_direct_write(dio->iocb, ret); 302 303 inode_dio_end(dio->inode); 304 305 if (flags & DIO_COMPLETE_ASYNC) { 306 /* 307 * generic_write_sync expects ki_pos to have been updated 308 * already, but the submission path only does this for 309 * synchronous I/O. 310 */ 311 dio->iocb->ki_pos += transferred; 312 313 if (ret > 0 && dio_op == REQ_OP_WRITE) 314 ret = generic_write_sync(dio->iocb, ret); 315 dio->iocb->ki_complete(dio->iocb, ret); 316 } 317 318 kmem_cache_free(dio_cache, dio); 319 return ret; 320} 321 322static void dio_aio_complete_work(struct work_struct *work) 323{ 324 struct dio *dio = container_of(work, struct dio, complete_work); 325 326 dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE); 327} 328 329static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio); 330 331/* 332 * Asynchronous IO callback. 333 */ 334static void dio_bio_end_aio(struct bio *bio) 335{ 336 struct dio *dio = bio->bi_private; 337 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 338 unsigned long remaining; 339 unsigned long flags; 340 bool defer_completion = false; 341 342 /* cleanup the bio */ 343 dio_bio_complete(dio, bio); 344 345 spin_lock_irqsave(&dio->bio_lock, flags); 346 remaining = --dio->refcount; 347 if (remaining == 1 && dio->waiter) 348 wake_up_process(dio->waiter); 349 spin_unlock_irqrestore(&dio->bio_lock, flags); 350 351 if (remaining == 0) { 352 /* 353 * Defer completion when defer_completion is set or 354 * when the inode has pages mapped and this is AIO write. 355 * We need to invalidate those pages because there is a 356 * chance they contain stale data in the case buffered IO 357 * went in between AIO submission and completion into the 358 * same region. 359 */ 360 if (dio->result) 361 defer_completion = dio->defer_completion || 362 (dio_op == REQ_OP_WRITE && 363 dio->inode->i_mapping->nrpages); 364 if (defer_completion) { 365 INIT_WORK(&dio->complete_work, dio_aio_complete_work); 366 queue_work(dio->inode->i_sb->s_dio_done_wq, 367 &dio->complete_work); 368 } else { 369 dio_complete(dio, 0, DIO_COMPLETE_ASYNC); 370 } 371 } 372} 373 374/* 375 * The BIO completion handler simply queues the BIO up for the process-context 376 * handler. 377 * 378 * During I/O bi_private points at the dio. After I/O, bi_private is used to 379 * implement a singly-linked list of completed BIOs, at dio->bio_list. 380 */ 381static void dio_bio_end_io(struct bio *bio) 382{ 383 struct dio *dio = bio->bi_private; 384 unsigned long flags; 385 386 spin_lock_irqsave(&dio->bio_lock, flags); 387 bio->bi_private = dio->bio_list; 388 dio->bio_list = bio; 389 if (--dio->refcount == 1 && dio->waiter) 390 wake_up_process(dio->waiter); 391 spin_unlock_irqrestore(&dio->bio_lock, flags); 392} 393 394static inline void 395dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, 396 struct block_device *bdev, 397 sector_t first_sector, int nr_vecs) 398{ 399 struct bio *bio; 400 401 /* 402 * bio_alloc() is guaranteed to return a bio when allowed to sleep and 403 * we request a valid number of vectors. 404 */ 405 bio = bio_alloc(bdev, nr_vecs, dio->opf, GFP_KERNEL); 406 bio->bi_iter.bi_sector = first_sector; 407 if (dio->is_async) 408 bio->bi_end_io = dio_bio_end_aio; 409 else 410 bio->bi_end_io = dio_bio_end_io; 411 if (dio->is_pinned) 412 bio_set_flag(bio, BIO_PAGE_PINNED); 413 sdio->bio = bio; 414 sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; 415} 416 417/* 418 * In the AIO read case we speculatively dirty the pages before starting IO. 419 * During IO completion, any of these pages which happen to have been written 420 * back will be redirtied by bio_check_pages_dirty(). 421 * 422 * bios hold a dio reference between submit_bio and ->end_io. 423 */ 424static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) 425{ 426 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 427 struct bio *bio = sdio->bio; 428 unsigned long flags; 429 430 bio->bi_private = dio; 431 432 spin_lock_irqsave(&dio->bio_lock, flags); 433 dio->refcount++; 434 spin_unlock_irqrestore(&dio->bio_lock, flags); 435 436 if (dio->is_async && dio_op == REQ_OP_READ && dio->should_dirty) 437 bio_set_pages_dirty(bio); 438 439 dio->bio_disk = bio->bi_bdev->bd_disk; 440 441 submit_bio(bio); 442 443 sdio->bio = NULL; 444 sdio->boundary = 0; 445 sdio->logical_offset_in_bio = 0; 446} 447 448/* 449 * Release any resources in case of a failure 450 */ 451static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio) 452{ 453 if (dio->is_pinned) 454 unpin_user_pages(dio->pages + sdio->head, 455 sdio->tail - sdio->head); 456 sdio->head = sdio->tail; 457} 458 459/* 460 * Wait for the next BIO to complete. Remove it and return it. NULL is 461 * returned once all BIOs have been completed. This must only be called once 462 * all bios have been issued so that dio->refcount can only decrease. This 463 * requires that the caller hold a reference on the dio. 464 */ 465static struct bio *dio_await_one(struct dio *dio) 466{ 467 unsigned long flags; 468 struct bio *bio = NULL; 469 470 spin_lock_irqsave(&dio->bio_lock, flags); 471 472 /* 473 * Wait as long as the list is empty and there are bios in flight. bio 474 * completion drops the count, maybe adds to the list, and wakes while 475 * holding the bio_lock so we don't need set_current_state()'s barrier 476 * and can call it after testing our condition. 477 */ 478 while (dio->refcount > 1 && dio->bio_list == NULL) { 479 __set_current_state(TASK_UNINTERRUPTIBLE); 480 dio->waiter = current; 481 spin_unlock_irqrestore(&dio->bio_lock, flags); 482 blk_io_schedule(); 483 /* wake up sets us TASK_RUNNING */ 484 spin_lock_irqsave(&dio->bio_lock, flags); 485 dio->waiter = NULL; 486 } 487 if (dio->bio_list) { 488 bio = dio->bio_list; 489 dio->bio_list = bio->bi_private; 490 } 491 spin_unlock_irqrestore(&dio->bio_lock, flags); 492 return bio; 493} 494 495/* 496 * Process one completed BIO. No locks are held. 497 */ 498static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio) 499{ 500 blk_status_t err = bio->bi_status; 501 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 502 bool should_dirty = dio_op == REQ_OP_READ && dio->should_dirty; 503 504 if (err) { 505 if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) 506 dio->io_error = -EAGAIN; 507 else 508 dio->io_error = -EIO; 509 } 510 511 if (dio->is_async && should_dirty) { 512 bio_check_pages_dirty(bio); /* transfers ownership */ 513 } else { 514 bio_release_pages(bio, should_dirty); 515 bio_put(bio); 516 } 517 return err; 518} 519 520/* 521 * Wait on and process all in-flight BIOs. This must only be called once 522 * all bios have been issued so that the refcount can only decrease. 523 * This just waits for all bios to make it through dio_bio_complete. IO 524 * errors are propagated through dio->io_error and should be propagated via 525 * dio_complete(). 526 */ 527static void dio_await_completion(struct dio *dio) 528{ 529 struct bio *bio; 530 do { 531 bio = dio_await_one(dio); 532 if (bio) 533 dio_bio_complete(dio, bio); 534 } while (bio); 535} 536 537/* 538 * A really large O_DIRECT read or write can generate a lot of BIOs. So 539 * to keep the memory consumption sane we periodically reap any completed BIOs 540 * during the BIO generation phase. 541 * 542 * This also helps to limit the peak amount of pinned userspace memory. 543 */ 544static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) 545{ 546 int ret = 0; 547 548 if (sdio->reap_counter++ >= 64) { 549 while (dio->bio_list) { 550 unsigned long flags; 551 struct bio *bio; 552 int ret2; 553 554 spin_lock_irqsave(&dio->bio_lock, flags); 555 bio = dio->bio_list; 556 dio->bio_list = bio->bi_private; 557 spin_unlock_irqrestore(&dio->bio_lock, flags); 558 ret2 = blk_status_to_errno(dio_bio_complete(dio, bio)); 559 if (ret == 0) 560 ret = ret2; 561 } 562 sdio->reap_counter = 0; 563 } 564 return ret; 565} 566 567static int dio_set_defer_completion(struct dio *dio) 568{ 569 struct super_block *sb = dio->inode->i_sb; 570 571 if (dio->defer_completion) 572 return 0; 573 dio->defer_completion = true; 574 if (!sb->s_dio_done_wq) 575 return sb_init_dio_done_wq(sb); 576 return 0; 577} 578 579/* 580 * Call into the fs to map some more disk blocks. We record the current number 581 * of available blocks at sdio->blocks_available. These are in units of the 582 * fs blocksize, i_blocksize(inode). 583 * 584 * The fs is allowed to map lots of blocks at once. If it wants to do that, 585 * it uses the passed inode-relative block number as the file offset, as usual. 586 * 587 * get_block() is passed the number of i_blkbits-sized blocks which direct_io 588 * has remaining to do. The fs should not map more than this number of blocks. 589 * 590 * If the fs has mapped a lot of blocks, it should populate bh->b_size to 591 * indicate how much contiguous disk space has been made available at 592 * bh->b_blocknr. 593 * 594 * If *any* of the mapped blocks are new, then the fs must set buffer_new(). 595 * This isn't very efficient... 596 * 597 * In the case of filesystem holes: the fs may return an arbitrarily-large 598 * hole by returning an appropriate value in b_size and by clearing 599 * buffer_mapped(). However the direct-io code will only process holes one 600 * block at a time - it will repeatedly call get_block() as it walks the hole. 601 */ 602static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, 603 struct buffer_head *map_bh) 604{ 605 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 606 int ret; 607 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ 608 sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ 609 unsigned long fs_count; /* Number of filesystem-sized blocks */ 610 int create; 611 unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; 612 loff_t i_size; 613 614 /* 615 * If there was a memory error and we've overwritten all the 616 * mapped blocks then we can now return that memory error 617 */ 618 ret = dio->page_errors; 619 if (ret == 0) { 620 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); 621 fs_startblk = sdio->block_in_file >> sdio->blkfactor; 622 fs_endblk = (sdio->final_block_in_request - 1) >> 623 sdio->blkfactor; 624 fs_count = fs_endblk - fs_startblk + 1; 625 626 map_bh->b_state = 0; 627 map_bh->b_size = fs_count << i_blkbits; 628 629 /* 630 * For writes that could fill holes inside i_size on a 631 * DIO_SKIP_HOLES filesystem we forbid block creations: only 632 * overwrites are permitted. We will return early to the caller 633 * once we see an unmapped buffer head returned, and the caller 634 * will fall back to buffered I/O. 635 * 636 * Otherwise the decision is left to the get_blocks method, 637 * which may decide to handle it or also return an unmapped 638 * buffer head. 639 */ 640 create = dio_op == REQ_OP_WRITE; 641 if (dio->flags & DIO_SKIP_HOLES) { 642 i_size = i_size_read(dio->inode); 643 if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits) 644 create = 0; 645 } 646 647 ret = (*sdio->get_block)(dio->inode, fs_startblk, 648 map_bh, create); 649 650 /* Store for completion */ 651 dio->private = map_bh->b_private; 652 653 if (ret == 0 && buffer_defer_completion(map_bh)) 654 ret = dio_set_defer_completion(dio); 655 } 656 return ret; 657} 658 659/* 660 * There is no bio. Make one now. 661 */ 662static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, 663 sector_t start_sector, struct buffer_head *map_bh) 664{ 665 sector_t sector; 666 int ret, nr_pages; 667 668 ret = dio_bio_reap(dio, sdio); 669 if (ret) 670 goto out; 671 sector = start_sector << (sdio->blkbits - 9); 672 nr_pages = bio_max_segs(sdio->pages_in_io); 673 BUG_ON(nr_pages <= 0); 674 dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); 675 sdio->boundary = 0; 676out: 677 return ret; 678} 679 680/* 681 * Attempt to put the current chunk of 'cur_page' into the current BIO. If 682 * that was successful then update final_block_in_bio and take a ref against 683 * the just-added page. 684 * 685 * Return zero on success. Non-zero means the caller needs to start a new BIO. 686 */ 687static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio) 688{ 689 int ret; 690 691 ret = bio_add_page(sdio->bio, sdio->cur_page, 692 sdio->cur_page_len, sdio->cur_page_offset); 693 if (ret == sdio->cur_page_len) { 694 /* 695 * Decrement count only, if we are done with this page 696 */ 697 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) 698 sdio->pages_in_io--; 699 dio_pin_page(dio, sdio->cur_page); 700 sdio->final_block_in_bio = sdio->cur_page_block + 701 (sdio->cur_page_len >> sdio->blkbits); 702 ret = 0; 703 } else { 704 ret = 1; 705 } 706 return ret; 707} 708 709/* 710 * Put cur_page under IO. The section of cur_page which is described by 711 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page 712 * starts on-disk at cur_page_block. 713 * 714 * We take a ref against the page here (on behalf of its presence in the bio). 715 * 716 * The caller of this function is responsible for removing cur_page from the 717 * dio, and for dropping the refcount which came from that presence. 718 */ 719static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, 720 struct buffer_head *map_bh) 721{ 722 int ret = 0; 723 724 if (sdio->bio) { 725 loff_t cur_offset = sdio->cur_page_fs_offset; 726 loff_t bio_next_offset = sdio->logical_offset_in_bio + 727 sdio->bio->bi_iter.bi_size; 728 729 /* 730 * See whether this new request is contiguous with the old. 731 * 732 * Btrfs cannot handle having logically non-contiguous requests 733 * submitted. For example if you have 734 * 735 * Logical: [0-4095][HOLE][8192-12287] 736 * Physical: [0-4095] [4096-8191] 737 * 738 * We cannot submit those pages together as one BIO. So if our 739 * current logical offset in the file does not equal what would 740 * be the next logical offset in the bio, submit the bio we 741 * have. 742 */ 743 if (sdio->final_block_in_bio != sdio->cur_page_block || 744 cur_offset != bio_next_offset) 745 dio_bio_submit(dio, sdio); 746 } 747 748 if (sdio->bio == NULL) { 749 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); 750 if (ret) 751 goto out; 752 } 753 754 if (dio_bio_add_page(dio, sdio) != 0) { 755 dio_bio_submit(dio, sdio); 756 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); 757 if (ret == 0) { 758 ret = dio_bio_add_page(dio, sdio); 759 BUG_ON(ret != 0); 760 } 761 } 762out: 763 return ret; 764} 765 766/* 767 * An autonomous function to put a chunk of a page under deferred IO. 768 * 769 * The caller doesn't actually know (or care) whether this piece of page is in 770 * a BIO, or is under IO or whatever. We just take care of all possible 771 * situations here. The separation between the logic of do_direct_IO() and 772 * that of submit_page_section() is important for clarity. Please don't break. 773 * 774 * The chunk of page starts on-disk at blocknr. 775 * 776 * We perform deferred IO, by recording the last-submitted page inside our 777 * private part of the dio structure. If possible, we just expand the IO 778 * across that page here. 779 * 780 * If that doesn't work out then we put the old page into the bio and add this 781 * page to the dio instead. 782 */ 783static inline int 784submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, 785 unsigned offset, unsigned len, sector_t blocknr, 786 struct buffer_head *map_bh) 787{ 788 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 789 int ret = 0; 790 int boundary = sdio->boundary; /* dio_send_cur_page may clear it */ 791 792 if (dio_op == REQ_OP_WRITE) { 793 /* 794 * Read accounting is performed in submit_bio() 795 */ 796 task_io_account_write(len); 797 } 798 799 /* 800 * Can we just grow the current page's presence in the dio? 801 */ 802 if (sdio->cur_page == page && 803 sdio->cur_page_offset + sdio->cur_page_len == offset && 804 sdio->cur_page_block + 805 (sdio->cur_page_len >> sdio->blkbits) == blocknr) { 806 sdio->cur_page_len += len; 807 goto out; 808 } 809 810 /* 811 * If there's a deferred page already there then send it. 812 */ 813 if (sdio->cur_page) { 814 ret = dio_send_cur_page(dio, sdio, map_bh); 815 dio_unpin_page(dio, sdio->cur_page); 816 sdio->cur_page = NULL; 817 if (ret) 818 return ret; 819 } 820 821 dio_pin_page(dio, page); /* It is in dio */ 822 sdio->cur_page = page; 823 sdio->cur_page_offset = offset; 824 sdio->cur_page_len = len; 825 sdio->cur_page_block = blocknr; 826 sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; 827out: 828 /* 829 * If boundary then we want to schedule the IO now to 830 * avoid metadata seeks. 831 */ 832 if (boundary) { 833 ret = dio_send_cur_page(dio, sdio, map_bh); 834 if (sdio->bio) 835 dio_bio_submit(dio, sdio); 836 dio_unpin_page(dio, sdio->cur_page); 837 sdio->cur_page = NULL; 838 } 839 return ret; 840} 841 842/* 843 * If we are not writing the entire block and get_block() allocated 844 * the block for us, we need to fill-in the unused portion of the 845 * block with zeros. This happens only if user-buffer, fileoffset or 846 * io length is not filesystem block-size multiple. 847 * 848 * `end' is zero if we're doing the start of the IO, 1 at the end of the 849 * IO. 850 */ 851static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, 852 int end, struct buffer_head *map_bh) 853{ 854 unsigned dio_blocks_per_fs_block; 855 unsigned this_chunk_blocks; /* In dio_blocks */ 856 unsigned this_chunk_bytes; 857 struct page *page; 858 859 sdio->start_zero_done = 1; 860 if (!sdio->blkfactor || !buffer_new(map_bh)) 861 return; 862 863 dio_blocks_per_fs_block = 1 << sdio->blkfactor; 864 this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); 865 866 if (!this_chunk_blocks) 867 return; 868 869 /* 870 * We need to zero out part of an fs block. It is either at the 871 * beginning or the end of the fs block. 872 */ 873 if (end) 874 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; 875 876 this_chunk_bytes = this_chunk_blocks << sdio->blkbits; 877 878 page = ZERO_PAGE(0); 879 if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, 880 sdio->next_block_for_io, map_bh)) 881 return; 882 883 sdio->next_block_for_io += this_chunk_blocks; 884} 885 886/* 887 * Walk the user pages, and the file, mapping blocks to disk and generating 888 * a sequence of (page,offset,len,block) mappings. These mappings are injected 889 * into submit_page_section(), which takes care of the next stage of submission 890 * 891 * Direct IO against a blockdev is different from a file. Because we can 892 * happily perform page-sized but 512-byte aligned IOs. It is important that 893 * blockdev IO be able to have fine alignment and large sizes. 894 * 895 * So what we do is to permit the ->get_block function to populate bh.b_size 896 * with the size of IO which is permitted at this offset and this i_blkbits. 897 * 898 * For best results, the blockdev should be set up with 512-byte i_blkbits and 899 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives 900 * fine alignment but still allows this function to work in PAGE_SIZE units. 901 */ 902static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, 903 struct buffer_head *map_bh) 904{ 905 const enum req_op dio_op = dio->opf & REQ_OP_MASK; 906 const unsigned blkbits = sdio->blkbits; 907 const unsigned i_blkbits = blkbits + sdio->blkfactor; 908 int ret = 0; 909 910 while (sdio->block_in_file < sdio->final_block_in_request) { 911 struct page *page; 912 size_t from, to; 913 914 page = dio_get_page(dio, sdio); 915 if (IS_ERR(page)) { 916 ret = PTR_ERR(page); 917 goto out; 918 } 919 from = sdio->head ? 0 : sdio->from; 920 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; 921 sdio->head++; 922 923 while (from < to) { 924 unsigned this_chunk_bytes; /* # of bytes mapped */ 925 unsigned this_chunk_blocks; /* # of blocks */ 926 unsigned u; 927 928 if (sdio->blocks_available == 0) { 929 /* 930 * Need to go and map some more disk 931 */ 932 unsigned long blkmask; 933 unsigned long dio_remainder; 934 935 ret = get_more_blocks(dio, sdio, map_bh); 936 if (ret) { 937 dio_unpin_page(dio, page); 938 goto out; 939 } 940 if (!buffer_mapped(map_bh)) 941 goto do_holes; 942 943 sdio->blocks_available = 944 map_bh->b_size >> blkbits; 945 sdio->next_block_for_io = 946 map_bh->b_blocknr << sdio->blkfactor; 947 if (buffer_new(map_bh)) { 948 clean_bdev_aliases( 949 map_bh->b_bdev, 950 map_bh->b_blocknr, 951 map_bh->b_size >> i_blkbits); 952 } 953 954 if (!sdio->blkfactor) 955 goto do_holes; 956 957 blkmask = (1 << sdio->blkfactor) - 1; 958 dio_remainder = (sdio->block_in_file & blkmask); 959 960 /* 961 * If we are at the start of IO and that IO 962 * starts partway into a fs-block, 963 * dio_remainder will be non-zero. If the IO 964 * is a read then we can simply advance the IO 965 * cursor to the first block which is to be 966 * read. But if the IO is a write and the 967 * block was newly allocated we cannot do that; 968 * the start of the fs block must be zeroed out 969 * on-disk 970 */ 971 if (!buffer_new(map_bh)) 972 sdio->next_block_for_io += dio_remainder; 973 sdio->blocks_available -= dio_remainder; 974 } 975do_holes: 976 /* Handle holes */ 977 if (!buffer_mapped(map_bh)) { 978 loff_t i_size_aligned; 979 980 /* AKPM: eargh, -ENOTBLK is a hack */ 981 if (dio_op == REQ_OP_WRITE) { 982 dio_unpin_page(dio, page); 983 return -ENOTBLK; 984 } 985 986 /* 987 * Be sure to account for a partial block as the 988 * last block in the file 989 */ 990 i_size_aligned = ALIGN(i_size_read(dio->inode), 991 1 << blkbits); 992 if (sdio->block_in_file >= 993 i_size_aligned >> blkbits) { 994 /* We hit eof */ 995 dio_unpin_page(dio, page); 996 goto out; 997 } 998 zero_user(page, from, 1 << blkbits); 999 sdio->block_in_file++; 1000 from += 1 << blkbits; 1001 dio->result += 1 << blkbits; 1002 goto next_block; 1003 } 1004 1005 /* 1006 * If we're performing IO which has an alignment which 1007 * is finer than the underlying fs, go check to see if 1008 * we must zero out the start of this block. 1009 */ 1010 if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) 1011 dio_zero_block(dio, sdio, 0, map_bh); 1012 1013 /* 1014 * Work out, in this_chunk_blocks, how much disk we 1015 * can add to this page 1016 */ 1017 this_chunk_blocks = sdio->blocks_available; 1018 u = (to - from) >> blkbits; 1019 if (this_chunk_blocks > u) 1020 this_chunk_blocks = u; 1021 u = sdio->final_block_in_request - sdio->block_in_file; 1022 if (this_chunk_blocks > u) 1023 this_chunk_blocks = u; 1024 this_chunk_bytes = this_chunk_blocks << blkbits; 1025 BUG_ON(this_chunk_bytes == 0); 1026 1027 if (this_chunk_blocks == sdio->blocks_available) 1028 sdio->boundary = buffer_boundary(map_bh); 1029 ret = submit_page_section(dio, sdio, page, 1030 from, 1031 this_chunk_bytes, 1032 sdio->next_block_for_io, 1033 map_bh); 1034 if (ret) { 1035 dio_unpin_page(dio, page); 1036 goto out; 1037 } 1038 sdio->next_block_for_io += this_chunk_blocks; 1039 1040 sdio->block_in_file += this_chunk_blocks; 1041 from += this_chunk_bytes; 1042 dio->result += this_chunk_bytes; 1043 sdio->blocks_available -= this_chunk_blocks; 1044next_block: 1045 BUG_ON(sdio->block_in_file > sdio->final_block_in_request); 1046 if (sdio->block_in_file == sdio->final_block_in_request) 1047 break; 1048 } 1049 1050 /* Drop the pin which was taken in get_user_pages() */ 1051 dio_unpin_page(dio, page); 1052 } 1053out: 1054 return ret; 1055} 1056 1057static inline int drop_refcount(struct dio *dio) 1058{ 1059 int ret2; 1060 unsigned long flags; 1061 1062 /* 1063 * Sync will always be dropping the final ref and completing the 1064 * operation. AIO can if it was a broken operation described above or 1065 * in fact if all the bios race to complete before we get here. In 1066 * that case dio_complete() translates the EIOCBQUEUED into the proper 1067 * return code that the caller will hand to ->complete(). 1068 * 1069 * This is managed by the bio_lock instead of being an atomic_t so that 1070 * completion paths can drop their ref and use the remaining count to 1071 * decide to wake the submission path atomically. 1072 */ 1073 spin_lock_irqsave(&dio->bio_lock, flags); 1074 ret2 = --dio->refcount; 1075 spin_unlock_irqrestore(&dio->bio_lock, flags); 1076 return ret2; 1077} 1078 1079/* 1080 * This is a library function for use by filesystem drivers. 1081 * 1082 * The locking rules are governed by the flags parameter: 1083 * - if the flags value contains DIO_LOCKING we use a fancy locking 1084 * scheme for dumb filesystems. 1085 * For writes this function is called under i_mutex and returns with 1086 * i_mutex held, for reads, i_mutex is not held on entry, but it is 1087 * taken and dropped again before returning. 1088 * - if the flags value does NOT contain DIO_LOCKING we don't use any 1089 * internal locking but rather rely on the filesystem to synchronize 1090 * direct I/O reads/writes versus each other and truncate. 1091 * 1092 * To help with locking against truncate we incremented the i_dio_count 1093 * counter before starting direct I/O, and decrement it once we are done. 1094 * Truncate can wait for it to reach zero to provide exclusion. It is 1095 * expected that filesystem provide exclusion between new direct I/O 1096 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, 1097 * but other filesystems need to take care of this on their own. 1098 * 1099 * NOTE: if you pass "sdio" to anything by pointer make sure that function 1100 * is always inlined. Otherwise gcc is unable to split the structure into 1101 * individual fields and will generate much worse code. This is important 1102 * for the whole file. 1103 */ 1104ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, 1105 struct block_device *bdev, struct iov_iter *iter, 1106 get_block_t get_block, dio_iodone_t end_io, 1107 int flags) 1108{ 1109 unsigned i_blkbits = READ_ONCE(inode->i_blkbits); 1110 unsigned blkbits = i_blkbits; 1111 unsigned blocksize_mask = (1 << blkbits) - 1; 1112 ssize_t retval = -EINVAL; 1113 const size_t count = iov_iter_count(iter); 1114 loff_t offset = iocb->ki_pos; 1115 const loff_t end = offset + count; 1116 struct dio *dio; 1117 struct dio_submit sdio = { 0, }; 1118 struct buffer_head map_bh = { 0, }; 1119 struct blk_plug plug; 1120 unsigned long align = offset | iov_iter_alignment(iter); 1121 1122 /* 1123 * Avoid references to bdev if not absolutely needed to give 1124 * the early prefetch in the caller enough time. 1125 */ 1126 1127 /* watch out for a 0 len io from a tricksy fs */ 1128 if (iov_iter_rw(iter) == READ && !count) 1129 return 0; 1130 1131 dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); 1132 if (!dio) 1133 return -ENOMEM; 1134 /* 1135 * Believe it or not, zeroing out the page array caused a .5% 1136 * performance regression in a database benchmark. So, we take 1137 * care to only zero out what's needed. 1138 */ 1139 memset(dio, 0, offsetof(struct dio, pages)); 1140 1141 dio->flags = flags; 1142 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { 1143 /* will be released by direct_io_worker */ 1144 inode_lock(inode); 1145 } 1146 dio->is_pinned = iov_iter_extract_will_pin(iter); 1147 1148 /* Once we sampled i_size check for reads beyond EOF */ 1149 dio->i_size = i_size_read(inode); 1150 if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { 1151 retval = 0; 1152 goto fail_dio; 1153 } 1154 1155 if (align & blocksize_mask) { 1156 if (bdev) 1157 blkbits = blksize_bits(bdev_logical_block_size(bdev)); 1158 blocksize_mask = (1 << blkbits) - 1; 1159 if (align & blocksize_mask) 1160 goto fail_dio; 1161 } 1162 1163 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { 1164 struct address_space *mapping = iocb->ki_filp->f_mapping; 1165 1166 retval = filemap_write_and_wait_range(mapping, offset, end - 1); 1167 if (retval) 1168 goto fail_dio; 1169 } 1170 1171 /* 1172 * For file extending writes updating i_size before data writeouts 1173 * complete can expose uninitialized blocks in dumb filesystems. 1174 * In that case we need to wait for I/O completion even if asked 1175 * for an asynchronous write. 1176 */ 1177 if (is_sync_kiocb(iocb)) 1178 dio->is_async = false; 1179 else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode)) 1180 dio->is_async = false; 1181 else 1182 dio->is_async = true; 1183 1184 dio->inode = inode; 1185 if (iov_iter_rw(iter) == WRITE) { 1186 dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; 1187 if (iocb->ki_flags & IOCB_NOWAIT) 1188 dio->opf |= REQ_NOWAIT; 1189 } else { 1190 dio->opf = REQ_OP_READ; 1191 } 1192 1193 /* 1194 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue 1195 * so that we can call ->fsync. 1196 */ 1197 if (dio->is_async && iov_iter_rw(iter) == WRITE) { 1198 retval = 0; 1199 if (iocb_is_dsync(iocb)) 1200 retval = dio_set_defer_completion(dio); 1201 else if (!dio->inode->i_sb->s_dio_done_wq) { 1202 /* 1203 * In case of AIO write racing with buffered read we 1204 * need to defer completion. We can't decide this now, 1205 * however the workqueue needs to be initialized here. 1206 */ 1207 retval = sb_init_dio_done_wq(dio->inode->i_sb); 1208 } 1209 if (retval) 1210 goto fail_dio; 1211 } 1212 1213 /* 1214 * Will be decremented at I/O completion time. 1215 */ 1216 inode_dio_begin(inode); 1217 1218 retval = 0; 1219 sdio.blkbits = blkbits; 1220 sdio.blkfactor = i_blkbits - blkbits; 1221 sdio.block_in_file = offset >> blkbits; 1222 1223 sdio.get_block = get_block; 1224 dio->end_io = end_io; 1225 sdio.final_block_in_bio = -1; 1226 sdio.next_block_for_io = -1; 1227 1228 dio->iocb = iocb; 1229 1230 spin_lock_init(&dio->bio_lock); 1231 dio->refcount = 1; 1232 1233 dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ; 1234 sdio.iter = iter; 1235 sdio.final_block_in_request = end >> blkbits; 1236 1237 /* 1238 * In case of non-aligned buffers, we may need 2 more 1239 * pages since we need to zero out first and last block. 1240 */ 1241 if (unlikely(sdio.blkfactor)) 1242 sdio.pages_in_io = 2; 1243 1244 sdio.pages_in_io += iov_iter_npages(iter, INT_MAX); 1245 1246 blk_start_plug(&plug); 1247 1248 retval = do_direct_IO(dio, &sdio, &map_bh); 1249 if (retval) 1250 dio_cleanup(dio, &sdio); 1251 1252 if (retval == -ENOTBLK) { 1253 /* 1254 * The remaining part of the request will be 1255 * handled by buffered I/O when we return 1256 */ 1257 retval = 0; 1258 } 1259 /* 1260 * There may be some unwritten disk at the end of a part-written 1261 * fs-block-sized block. Go zero that now. 1262 */ 1263 dio_zero_block(dio, &sdio, 1, &map_bh); 1264 1265 if (sdio.cur_page) { 1266 ssize_t ret2; 1267 1268 ret2 = dio_send_cur_page(dio, &sdio, &map_bh); 1269 if (retval == 0) 1270 retval = ret2; 1271 dio_unpin_page(dio, sdio.cur_page); 1272 sdio.cur_page = NULL; 1273 } 1274 if (sdio.bio) 1275 dio_bio_submit(dio, &sdio); 1276 1277 blk_finish_plug(&plug); 1278 1279 /* 1280 * It is possible that, we return short IO due to end of file. 1281 * In that case, we need to release all the pages we got hold on. 1282 */ 1283 dio_cleanup(dio, &sdio); 1284 1285 /* 1286 * All block lookups have been performed. For READ requests 1287 * we can let i_mutex go now that its achieved its purpose 1288 * of protecting us from looking up uninitialized blocks. 1289 */ 1290 if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING)) 1291 inode_unlock(dio->inode); 1292 1293 /* 1294 * The only time we want to leave bios in flight is when a successful 1295 * partial aio read or full aio write have been setup. In that case 1296 * bio completion will call aio_complete. The only time it's safe to 1297 * call aio_complete is when we return -EIOCBQUEUED, so we key on that. 1298 * This had *better* be the only place that raises -EIOCBQUEUED. 1299 */ 1300 BUG_ON(retval == -EIOCBQUEUED); 1301 if (dio->is_async && retval == 0 && dio->result && 1302 (iov_iter_rw(iter) == READ || dio->result == count)) 1303 retval = -EIOCBQUEUED; 1304 else 1305 dio_await_completion(dio); 1306 1307 if (drop_refcount(dio) == 0) { 1308 retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE); 1309 } else 1310 BUG_ON(retval != -EIOCBQUEUED); 1311 1312 return retval; 1313 1314fail_dio: 1315 if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) 1316 inode_unlock(inode); 1317 1318 kmem_cache_free(dio_cache, dio); 1319 return retval; 1320} 1321EXPORT_SYMBOL(__blockdev_direct_IO); 1322 1323static __init int dio_init(void) 1324{ 1325 dio_cache = KMEM_CACHE(dio, SLAB_PANIC); 1326 return 0; 1327} 1328module_init(dio_init) 1329