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