| 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 | |
| 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 /* This is async IO */ |
| 53 | #define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */ |
| 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 | /* dio_state only used in the submission path */ |
| 68 | |
| 69 | struct dio_submit { |
| 70 | struct bio *bio; /* bio under assembly */ |
| 71 | unsigned blkbits; /* doesn't change */ |
| 72 | unsigned blkfactor; /* When we're using an alignment which |
| 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; /* flag: sub-blocksize zeroing has |
| 78 | been performed at the start of a |
| 79 | write */ |
| 80 | int pages_in_io; /* approximate total IO pages */ |
| 81 | sector_t block_in_file; /* Current offset into the underlying |
| 82 | file in dio_block units. */ |
| 83 | unsigned blocks_available; /* At block_in_file. changes */ |
| 84 | int reap_counter; /* rate limit reaping */ |
| 85 | sector_t final_block_in_request;/* doesn't change */ |
| 86 | int boundary; /* prev block is at a boundary */ |
| 87 | get_block_t *get_block; /* block mapping function */ |
| 88 | |
| 89 | loff_t logical_offset_in_bio; /* current first logical block in bio */ |
| 90 | sector_t final_block_in_bio; /* current final block in bio + 1 */ |
| 91 | sector_t next_block_for_io; /* next block to be put under 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; /* The page */ |
| 100 | unsigned cur_page_offset; /* Offset into it, in bytes */ |
| 101 | unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ |
| 102 | sector_t cur_page_block; /* Where it starts */ |
| 103 | loff_t cur_page_fs_offset; /* Offset in file */ |
| 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; /* next page to process */ |
| 111 | unsigned tail; /* last valid page + 1 */ |
| 112 | size_t from, to; |
| 113 | }; |
| 114 | |
| 115 | /* dio_state communicated between submission path and end_io */ |
| 116 | struct dio { |
| 117 | int flags; /* doesn't change */ |
| 118 | blk_opf_t opf; /* request operation type and flags */ |
| 119 | struct gendisk *bio_disk; |
| 120 | struct inode *inode; |
| 121 | loff_t i_size; /* i_size when submitted */ |
| 122 | dio_iodone_t *end_io; /* IO completion function */ |
| 123 | bool is_pinned; /* T if we have pins on the pages */ |
| 124 | |
| 125 | void *private; /* copy from map_bh.b_private */ |
| 126 | |
| 127 | /* BIO completion state */ |
| 128 | spinlock_t bio_lock; /* protects BIO fields below */ |
| 129 | int page_errors; /* err from iov_iter_extract_pages() */ |
| 130 | int is_async; /* is IO async ? */ |
| 131 | bool defer_completion; /* defer AIO completion to workqueue? */ |
| 132 | bool should_dirty; /* if pages should be dirtied */ |
| 133 | int io_error; /* IO error in completion path */ |
| 134 | unsigned long refcount; /* direct_io_worker() and bios */ |
| 135 | struct bio *bio_list; /* singly linked via bi_private */ |
| 136 | struct task_struct *waiter; /* waiting task (NULL if none) */ |
| 137 | |
| 138 | /* AIO related stuff */ |
| 139 | struct kiocb *iocb; /* kiocb */ |
| 140 | ssize_t result; /* IO 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]; /* page buffer */ |
| 149 | struct work_struct complete_work;/* deferred AIO completion */ |
| 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) |
| 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 | * |
| 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) |
| 258 | ret = 0; |
| 259 | |
| 260 | if (dio->result) { |
| 261 | transferred = dio->result; |
| 262 | |
| 263 | /* Check for short read case */ |
| 264 | if (dio_op == REQ_OP_READ && |
| 265 | ((offset + transferred) > dio->i_size)) |
| 266 | transferred = dio->i_size - offset; |
| 267 | /* ignore EFAULT if some IO has been done */ |
| 268 | if (unlikely(ret == -EFAULT) && transferred) |
| 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 | // XXX: ki_pos?? |
| 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); |
| 301 | |
| 302 | inode_dio_end(dio->inode); |
| 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 | /* cleanup the bio */ |
| 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 | /* wake up sets us TASK_RUNNING */ |
| 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 | if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) |
| 507 | dio->io_error = -EAGAIN; |
| 508 | else |
| 509 | dio->io_error = -EIO; |
| 510 | } |
| 511 | |
| 512 | if (dio->is_async && should_dirty) { |
| 513 | bio_check_pages_dirty(bio); /* transfers ownership */ |
| 514 | } else { |
| 515 | bio_release_pages(bio, should_dirty); |
| 516 | bio_put(bio); |
| 517 | } |
| 518 | return err; |
| 519 | } |
| 520 | |
| 521 | /* |
| 522 | * Wait on and process all in-flight BIOs. This must only be called once |
| 523 | * all bios have been issued so that the refcount can only decrease. |
| 524 | * This just waits for all bios to make it through dio_bio_complete. IO |
| 525 | * errors are propagated through dio->io_error and should be propagated via |
| 526 | * dio_complete(). |
| 527 | */ |
| 528 | static void dio_await_completion(struct dio *dio) |
| 529 | { |
| 530 | struct bio *bio; |
| 531 | do { |
| 532 | bio = dio_await_one(dio); |
| 533 | if (bio) |
| 534 | dio_bio_complete(dio, bio); |
| 535 | } while (bio); |
| 536 | } |
| 537 | |
| 538 | /* |
| 539 | * A really large O_DIRECT read or write can generate a lot of BIOs. So |
| 540 | * to keep the memory consumption sane we periodically reap any completed BIOs |
| 541 | * during the BIO generation phase. |
| 542 | * |
| 543 | * This also helps to limit the peak amount of pinned userspace memory. |
| 544 | */ |
| 545 | static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) |
| 546 | { |
| 547 | int ret = 0; |
| 548 | |
| 549 | if (sdio->reap_counter++ >= 64) { |
| 550 | while (dio->bio_list) { |
| 551 | unsigned long flags; |
| 552 | struct bio *bio; |
| 553 | int ret2; |
| 554 | |
| 555 | spin_lock_irqsave(&dio->bio_lock, flags); |
| 556 | bio = dio->bio_list; |
| 557 | dio->bio_list = bio->bi_private; |
| 558 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
| 559 | ret2 = blk_status_to_errno(dio_bio_complete(dio, bio)); |
| 560 | if (ret == 0) |
| 561 | ret = ret2; |
| 562 | } |
| 563 | sdio->reap_counter = 0; |
| 564 | } |
| 565 | return ret; |
| 566 | } |
| 567 | |
| 568 | static int dio_set_defer_completion(struct dio *dio) |
| 569 | { |
| 570 | struct super_block *sb = dio->inode->i_sb; |
| 571 | |
| 572 | if (dio->defer_completion) |
| 573 | return 0; |
| 574 | dio->defer_completion = true; |
| 575 | if (!sb->s_dio_done_wq) |
| 576 | return sb_init_dio_done_wq(sb); |
| 577 | return 0; |
| 578 | } |
| 579 | |
| 580 | /* |
| 581 | * Call into the fs to map some more disk blocks. We record the current number |
| 582 | * of available blocks at sdio->blocks_available. These are in units of the |
| 583 | * fs blocksize, i_blocksize(inode). |
| 584 | * |
| 585 | * The fs is allowed to map lots of blocks at once. If it wants to do that, |
| 586 | * it uses the passed inode-relative block number as the file offset, as usual. |
| 587 | * |
| 588 | * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
| 589 | * has remaining to do. The fs should not map more than this number of blocks. |
| 590 | * |
| 591 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to |
| 592 | * indicate how much contiguous disk space has been made available at |
| 593 | * bh->b_blocknr. |
| 594 | * |
| 595 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). |
| 596 | * This isn't very efficient... |
| 597 | * |
| 598 | * In the case of filesystem holes: the fs may return an arbitrarily-large |
| 599 | * hole by returning an appropriate value in b_size and by clearing |
| 600 | * buffer_mapped(). However the direct-io code will only process holes one |
| 601 | * block at a time - it will repeatedly call get_block() as it walks the hole. |
| 602 | */ |
| 603 | static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, |
| 604 | struct buffer_head *map_bh) |
| 605 | { |
| 606 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
| 607 | int ret; |
| 608 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ |
| 609 | sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ |
| 610 | unsigned long fs_count; /* Number of filesystem-sized blocks */ |
| 611 | int create; |
| 612 | unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; |
| 613 | loff_t i_size; |
| 614 | |
| 615 | /* |
| 616 | * If there was a memory error and we've overwritten all the |
| 617 | * mapped blocks then we can now return that memory error |
| 618 | */ |
| 619 | ret = dio->page_errors; |
| 620 | if (ret == 0) { |
| 621 | BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); |
| 622 | fs_startblk = sdio->block_in_file >> sdio->blkfactor; |
| 623 | fs_endblk = (sdio->final_block_in_request - 1) >> |
| 624 | sdio->blkfactor; |
| 625 | fs_count = fs_endblk - fs_startblk + 1; |
| 626 | |
| 627 | map_bh->b_state = 0; |
| 628 | map_bh->b_size = fs_count << i_blkbits; |
| 629 | |
| 630 | /* |
| 631 | * For writes that could fill holes inside i_size on a |
| 632 | * DIO_SKIP_HOLES filesystem we forbid block creations: only |
| 633 | * overwrites are permitted. We will return early to the caller |
| 634 | * once we see an unmapped buffer head returned, and the caller |
| 635 | * will fall back to buffered I/O. |
| 636 | * |
| 637 | * Otherwise the decision is left to the get_blocks method, |
| 638 | * which may decide to handle it or also return an unmapped |
| 639 | * buffer head. |
| 640 | */ |
| 641 | create = dio_op == REQ_OP_WRITE; |
| 642 | if (dio->flags & DIO_SKIP_HOLES) { |
| 643 | i_size = i_size_read(dio->inode); |
| 644 | if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits) |
| 645 | create = 0; |
| 646 | } |
| 647 | |
| 648 | ret = (*sdio->get_block)(dio->inode, fs_startblk, |
| 649 | map_bh, create); |
| 650 | |
| 651 | /* Store for completion */ |
| 652 | dio->private = map_bh->b_private; |
| 653 | |
| 654 | if (ret == 0 && buffer_defer_completion(map_bh)) |
| 655 | ret = dio_set_defer_completion(dio); |
| 656 | } |
| 657 | return ret; |
| 658 | } |
| 659 | |
| 660 | /* |
| 661 | * There is no bio. Make one now. |
| 662 | */ |
| 663 | static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, |
| 664 | sector_t start_sector, struct buffer_head *map_bh) |
| 665 | { |
| 666 | sector_t sector; |
| 667 | int ret, nr_pages; |
| 668 | |
| 669 | ret = dio_bio_reap(dio, sdio); |
| 670 | if (ret) |
| 671 | goto out; |
| 672 | sector = start_sector << (sdio->blkbits - 9); |
| 673 | nr_pages = bio_max_segs(sdio->pages_in_io); |
| 674 | BUG_ON(nr_pages <= 0); |
| 675 | dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); |
| 676 | sdio->boundary = 0; |
| 677 | out: |
| 678 | return ret; |
| 679 | } |
| 680 | |
| 681 | /* |
| 682 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If |
| 683 | * that was successful then update final_block_in_bio and take a ref against |
| 684 | * the just-added page. |
| 685 | * |
| 686 | * Return zero on success. Non-zero means the caller needs to start a new BIO. |
| 687 | */ |
| 688 | static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio) |
| 689 | { |
| 690 | int ret; |
| 691 | |
| 692 | ret = bio_add_page(sdio->bio, sdio->cur_page, |
| 693 | sdio->cur_page_len, sdio->cur_page_offset); |
| 694 | if (ret == sdio->cur_page_len) { |
| 695 | /* |
| 696 | * Decrement count only, if we are done with this page |
| 697 | */ |
| 698 | if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) |
| 699 | sdio->pages_in_io--; |
| 700 | dio_pin_page(dio, sdio->cur_page); |
| 701 | sdio->final_block_in_bio = sdio->cur_page_block + |
| 702 | (sdio->cur_page_len >> sdio->blkbits); |
| 703 | ret = 0; |
| 704 | } else { |
| 705 | ret = 1; |
| 706 | } |
| 707 | return ret; |
| 708 | } |
| 709 | |
| 710 | /* |
| 711 | * Put cur_page under IO. The section of cur_page which is described by |
| 712 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page |
| 713 | * starts on-disk at cur_page_block. |
| 714 | * |
| 715 | * We take a ref against the page here (on behalf of its presence in the bio). |
| 716 | * |
| 717 | * The caller of this function is responsible for removing cur_page from the |
| 718 | * dio, and for dropping the refcount which came from that presence. |
| 719 | */ |
| 720 | static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, |
| 721 | struct buffer_head *map_bh) |
| 722 | { |
| 723 | int ret = 0; |
| 724 | |
| 725 | if (sdio->bio) { |
| 726 | loff_t cur_offset = sdio->cur_page_fs_offset; |
| 727 | loff_t bio_next_offset = sdio->logical_offset_in_bio + |
| 728 | sdio->bio->bi_iter.bi_size; |
| 729 | |
| 730 | /* |
| 731 | * See whether this new request is contiguous with the old. |
| 732 | * |
| 733 | * Btrfs cannot handle having logically non-contiguous requests |
| 734 | * submitted. For example if you have |
| 735 | * |
| 736 | * Logical: [0-4095][HOLE][8192-12287] |
| 737 | * Physical: [0-4095] [4096-8191] |
| 738 | * |
| 739 | * We cannot submit those pages together as one BIO. So if our |
| 740 | * current logical offset in the file does not equal what would |
| 741 | * be the next logical offset in the bio, submit the bio we |
| 742 | * have. |
| 743 | */ |
| 744 | if (sdio->final_block_in_bio != sdio->cur_page_block || |
| 745 | cur_offset != bio_next_offset) |
| 746 | dio_bio_submit(dio, sdio); |
| 747 | } |
| 748 | |
| 749 | if (sdio->bio == NULL) { |
| 750 | ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
| 751 | if (ret) |
| 752 | goto out; |
| 753 | } |
| 754 | |
| 755 | if (dio_bio_add_page(dio, sdio) != 0) { |
| 756 | dio_bio_submit(dio, sdio); |
| 757 | ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); |
| 758 | if (ret == 0) { |
| 759 | ret = dio_bio_add_page(dio, sdio); |
| 760 | BUG_ON(ret != 0); |
| 761 | } |
| 762 | } |
| 763 | out: |
| 764 | return ret; |
| 765 | } |
| 766 | |
| 767 | /* |
| 768 | * An autonomous function to put a chunk of a page under deferred IO. |
| 769 | * |
| 770 | * The caller doesn't actually know (or care) whether this piece of page is in |
| 771 | * a BIO, or is under IO or whatever. We just take care of all possible |
| 772 | * situations here. The separation between the logic of do_direct_IO() and |
| 773 | * that of submit_page_section() is important for clarity. Please don't break. |
| 774 | * |
| 775 | * The chunk of page starts on-disk at blocknr. |
| 776 | * |
| 777 | * We perform deferred IO, by recording the last-submitted page inside our |
| 778 | * private part of the dio structure. If possible, we just expand the IO |
| 779 | * across that page here. |
| 780 | * |
| 781 | * If that doesn't work out then we put the old page into the bio and add this |
| 782 | * page to the dio instead. |
| 783 | */ |
| 784 | static inline int |
| 785 | submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, |
| 786 | unsigned offset, unsigned len, sector_t blocknr, |
| 787 | struct buffer_head *map_bh) |
| 788 | { |
| 789 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
| 790 | int ret = 0; |
| 791 | int boundary = sdio->boundary; /* dio_send_cur_page may clear it */ |
| 792 | |
| 793 | if (dio_op == REQ_OP_WRITE) { |
| 794 | /* |
| 795 | * Read accounting is performed in submit_bio() |
| 796 | */ |
| 797 | task_io_account_write(len); |
| 798 | } |
| 799 | |
| 800 | /* |
| 801 | * Can we just grow the current page's presence in the dio? |
| 802 | */ |
| 803 | if (sdio->cur_page == page && |
| 804 | sdio->cur_page_offset + sdio->cur_page_len == offset && |
| 805 | sdio->cur_page_block + |
| 806 | (sdio->cur_page_len >> sdio->blkbits) == blocknr) { |
| 807 | sdio->cur_page_len += len; |
| 808 | goto out; |
| 809 | } |
| 810 | |
| 811 | /* |
| 812 | * If there's a deferred page already there then send it. |
| 813 | */ |
| 814 | if (sdio->cur_page) { |
| 815 | ret = dio_send_cur_page(dio, sdio, map_bh); |
| 816 | dio_unpin_page(dio, sdio->cur_page); |
| 817 | sdio->cur_page = NULL; |
| 818 | if (ret) |
| 819 | return ret; |
| 820 | } |
| 821 | |
| 822 | dio_pin_page(dio, page); /* It is in dio */ |
| 823 | sdio->cur_page = page; |
| 824 | sdio->cur_page_offset = offset; |
| 825 | sdio->cur_page_len = len; |
| 826 | sdio->cur_page_block = blocknr; |
| 827 | sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; |
| 828 | out: |
| 829 | /* |
| 830 | * If boundary then we want to schedule the IO now to |
| 831 | * avoid metadata seeks. |
| 832 | */ |
| 833 | if (boundary) { |
| 834 | ret = dio_send_cur_page(dio, sdio, map_bh); |
| 835 | if (sdio->bio) |
| 836 | dio_bio_submit(dio, sdio); |
| 837 | dio_unpin_page(dio, sdio->cur_page); |
| 838 | sdio->cur_page = NULL; |
| 839 | } |
| 840 | return ret; |
| 841 | } |
| 842 | |
| 843 | /* |
| 844 | * If we are not writing the entire block and get_block() allocated |
| 845 | * the block for us, we need to fill-in the unused portion of the |
| 846 | * block with zeros. This happens only if user-buffer, fileoffset or |
| 847 | * io length is not filesystem block-size multiple. |
| 848 | * |
| 849 | * `end' is zero if we're doing the start of the IO, 1 at the end of the |
| 850 | * IO. |
| 851 | */ |
| 852 | static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, |
| 853 | int end, struct buffer_head *map_bh) |
| 854 | { |
| 855 | unsigned dio_blocks_per_fs_block; |
| 856 | unsigned this_chunk_blocks; /* In dio_blocks */ |
| 857 | unsigned this_chunk_bytes; |
| 858 | struct page *page; |
| 859 | |
| 860 | sdio->start_zero_done = 1; |
| 861 | if (!sdio->blkfactor || !buffer_new(map_bh)) |
| 862 | return; |
| 863 | |
| 864 | dio_blocks_per_fs_block = 1 << sdio->blkfactor; |
| 865 | this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); |
| 866 | |
| 867 | if (!this_chunk_blocks) |
| 868 | return; |
| 869 | |
| 870 | /* |
| 871 | * We need to zero out part of an fs block. It is either at the |
| 872 | * beginning or the end of the fs block. |
| 873 | */ |
| 874 | if (end) |
| 875 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; |
| 876 | |
| 877 | this_chunk_bytes = this_chunk_blocks << sdio->blkbits; |
| 878 | |
| 879 | page = ZERO_PAGE(0); |
| 880 | if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, |
| 881 | sdio->next_block_for_io, map_bh)) |
| 882 | return; |
| 883 | |
| 884 | sdio->next_block_for_io += this_chunk_blocks; |
| 885 | } |
| 886 | |
| 887 | /* |
| 888 | * Walk the user pages, and the file, mapping blocks to disk and generating |
| 889 | * a sequence of (page,offset,len,block) mappings. These mappings are injected |
| 890 | * into submit_page_section(), which takes care of the next stage of submission |
| 891 | * |
| 892 | * Direct IO against a blockdev is different from a file. Because we can |
| 893 | * happily perform page-sized but 512-byte aligned IOs. It is important that |
| 894 | * blockdev IO be able to have fine alignment and large sizes. |
| 895 | * |
| 896 | * So what we do is to permit the ->get_block function to populate bh.b_size |
| 897 | * with the size of IO which is permitted at this offset and this i_blkbits. |
| 898 | * |
| 899 | * For best results, the blockdev should be set up with 512-byte i_blkbits and |
| 900 | * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
| 901 | * fine alignment but still allows this function to work in PAGE_SIZE units. |
| 902 | */ |
| 903 | static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, |
| 904 | struct buffer_head *map_bh) |
| 905 | { |
| 906 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
| 907 | const unsigned blkbits = sdio->blkbits; |
| 908 | const unsigned i_blkbits = blkbits + sdio->blkfactor; |
| 909 | int ret = 0; |
| 910 | |
| 911 | while (sdio->block_in_file < sdio->final_block_in_request) { |
| 912 | struct page *page; |
| 913 | size_t from, to; |
| 914 | |
| 915 | page = dio_get_page(dio, sdio); |
| 916 | if (IS_ERR(page)) { |
| 917 | ret = PTR_ERR(page); |
| 918 | goto out; |
| 919 | } |
| 920 | from = sdio->head ? 0 : sdio->from; |
| 921 | to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; |
| 922 | sdio->head++; |
| 923 | |
| 924 | while (from < to) { |
| 925 | unsigned this_chunk_bytes; /* # of bytes mapped */ |
| 926 | unsigned this_chunk_blocks; /* # of blocks */ |
| 927 | unsigned u; |
| 928 | |
| 929 | if (sdio->blocks_available == 0) { |
| 930 | /* |
| 931 | * Need to go and map some more disk |
| 932 | */ |
| 933 | unsigned long blkmask; |
| 934 | unsigned long dio_remainder; |
| 935 | |
| 936 | ret = get_more_blocks(dio, sdio, map_bh); |
| 937 | if (ret) { |
| 938 | dio_unpin_page(dio, page); |
| 939 | goto out; |
| 940 | } |
| 941 | if (!buffer_mapped(map_bh)) |
| 942 | goto do_holes; |
| 943 | |
| 944 | sdio->blocks_available = |
| 945 | map_bh->b_size >> blkbits; |
| 946 | sdio->next_block_for_io = |
| 947 | map_bh->b_blocknr << sdio->blkfactor; |
| 948 | if (buffer_new(map_bh)) { |
| 949 | clean_bdev_aliases( |
| 950 | map_bh->b_bdev, |
| 951 | map_bh->b_blocknr, |
| 952 | map_bh->b_size >> i_blkbits); |
| 953 | } |
| 954 | |
| 955 | if (!sdio->blkfactor) |
| 956 | goto do_holes; |
| 957 | |
| 958 | blkmask = (1 << sdio->blkfactor) - 1; |
| 959 | dio_remainder = (sdio->block_in_file & blkmask); |
| 960 | |
| 961 | /* |
| 962 | * If we are at the start of IO and that IO |
| 963 | * starts partway into a fs-block, |
| 964 | * dio_remainder will be non-zero. If the IO |
| 965 | * is a read then we can simply advance the IO |
| 966 | * cursor to the first block which is to be |
| 967 | * read. But if the IO is a write and the |
| 968 | * block was newly allocated we cannot do that; |
| 969 | * the start of the fs block must be zeroed out |
| 970 | * on-disk |
| 971 | */ |
| 972 | if (!buffer_new(map_bh)) |
| 973 | sdio->next_block_for_io += dio_remainder; |
| 974 | sdio->blocks_available -= dio_remainder; |
| 975 | } |
| 976 | do_holes: |
| 977 | /* Handle holes */ |
| 978 | if (!buffer_mapped(map_bh)) { |
| 979 | loff_t i_size_aligned; |
| 980 | |
| 981 | /* AKPM: eargh, -ENOTBLK is a hack */ |
| 982 | if (dio_op == REQ_OP_WRITE) { |
| 983 | dio_unpin_page(dio, page); |
| 984 | return -ENOTBLK; |
| 985 | } |
| 986 | |
| 987 | /* |
| 988 | * Be sure to account for a partial block as the |
| 989 | * last block in the file |
| 990 | */ |
| 991 | i_size_aligned = ALIGN(i_size_read(dio->inode), |
| 992 | 1 << blkbits); |
| 993 | if (sdio->block_in_file >= |
| 994 | i_size_aligned >> blkbits) { |
| 995 | /* We hit eof */ |
| 996 | dio_unpin_page(dio, page); |
| 997 | goto out; |
| 998 | } |
| 999 | zero_user(page, from, 1 << blkbits); |
| 1000 | sdio->block_in_file++; |
| 1001 | from += 1 << blkbits; |
| 1002 | dio->result += 1 << blkbits; |
| 1003 | goto next_block; |
| 1004 | } |
| 1005 | |
| 1006 | /* |
| 1007 | * If we're performing IO which has an alignment which |
| 1008 | * is finer than the underlying fs, go check to see if |
| 1009 | * we must zero out the start of this block. |
| 1010 | */ |
| 1011 | if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) |
| 1012 | dio_zero_block(dio, sdio, 0, map_bh); |
| 1013 | |
| 1014 | /* |
| 1015 | * Work out, in this_chunk_blocks, how much disk we |
| 1016 | * can add to this page |
| 1017 | */ |
| 1018 | this_chunk_blocks = sdio->blocks_available; |
| 1019 | u = (to - from) >> blkbits; |
| 1020 | if (this_chunk_blocks > u) |
| 1021 | this_chunk_blocks = u; |
| 1022 | u = sdio->final_block_in_request - sdio->block_in_file; |
| 1023 | if (this_chunk_blocks > u) |
| 1024 | this_chunk_blocks = u; |
| 1025 | this_chunk_bytes = this_chunk_blocks << blkbits; |
| 1026 | BUG_ON(this_chunk_bytes == 0); |
| 1027 | |
| 1028 | if (this_chunk_blocks == sdio->blocks_available) |
| 1029 | sdio->boundary = buffer_boundary(map_bh); |
| 1030 | ret = submit_page_section(dio, sdio, page, |
| 1031 | from, |
| 1032 | this_chunk_bytes, |
| 1033 | sdio->next_block_for_io, |
| 1034 | map_bh); |
| 1035 | if (ret) { |
| 1036 | dio_unpin_page(dio, page); |
| 1037 | goto out; |
| 1038 | } |
| 1039 | sdio->next_block_for_io += this_chunk_blocks; |
| 1040 | |
| 1041 | sdio->block_in_file += this_chunk_blocks; |
| 1042 | from += this_chunk_bytes; |
| 1043 | dio->result += this_chunk_bytes; |
| 1044 | sdio->blocks_available -= this_chunk_blocks; |
| 1045 | next_block: |
| 1046 | BUG_ON(sdio->block_in_file > sdio->final_block_in_request); |
| 1047 | if (sdio->block_in_file == sdio->final_block_in_request) |
| 1048 | break; |
| 1049 | } |
| 1050 | |
| 1051 | /* Drop the pin which was taken in get_user_pages() */ |
| 1052 | dio_unpin_page(dio, page); |
| 1053 | } |
| 1054 | out: |
| 1055 | return ret; |
| 1056 | } |
| 1057 | |
| 1058 | static inline int drop_refcount(struct dio *dio) |
| 1059 | { |
| 1060 | int ret2; |
| 1061 | unsigned long flags; |
| 1062 | |
| 1063 | /* |
| 1064 | * Sync will always be dropping the final ref and completing the |
| 1065 | * operation. AIO can if it was a broken operation described above or |
| 1066 | * in fact if all the bios race to complete before we get here. In |
| 1067 | * that case dio_complete() translates the EIOCBQUEUED into the proper |
| 1068 | * return code that the caller will hand to ->complete(). |
| 1069 | * |
| 1070 | * This is managed by the bio_lock instead of being an atomic_t so that |
| 1071 | * completion paths can drop their ref and use the remaining count to |
| 1072 | * decide to wake the submission path atomically. |
| 1073 | */ |
| 1074 | spin_lock_irqsave(&dio->bio_lock, flags); |
| 1075 | ret2 = --dio->refcount; |
| 1076 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
| 1077 | return ret2; |
| 1078 | } |
| 1079 | |
| 1080 | /* |
| 1081 | * This is a library function for use by filesystem drivers. |
| 1082 | * |
| 1083 | * The locking rules are governed by the flags parameter: |
| 1084 | * - if the flags value contains DIO_LOCKING we use a fancy locking |
| 1085 | * scheme for dumb filesystems. |
| 1086 | * For writes this function is called under i_mutex and returns with |
| 1087 | * i_mutex held, for reads, i_mutex is not held on entry, but it is |
| 1088 | * taken and dropped again before returning. |
| 1089 | * - if the flags value does NOT contain DIO_LOCKING we don't use any |
| 1090 | * internal locking but rather rely on the filesystem to synchronize |
| 1091 | * direct I/O reads/writes versus each other and truncate. |
| 1092 | * |
| 1093 | * To help with locking against truncate we incremented the i_dio_count |
| 1094 | * counter before starting direct I/O, and decrement it once we are done. |
| 1095 | * Truncate can wait for it to reach zero to provide exclusion. It is |
| 1096 | * expected that filesystem provide exclusion between new direct I/O |
| 1097 | * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, |
| 1098 | * but other filesystems need to take care of this on their own. |
| 1099 | * |
| 1100 | * NOTE: if you pass "sdio" to anything by pointer make sure that function |
| 1101 | * is always inlined. Otherwise gcc is unable to split the structure into |
| 1102 | * individual fields and will generate much worse code. This is important |
| 1103 | * for the whole file. |
| 1104 | */ |
| 1105 | ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, |
| 1106 | struct block_device *bdev, struct iov_iter *iter, |
| 1107 | get_block_t get_block, dio_iodone_t end_io, |
| 1108 | int flags) |
| 1109 | { |
| 1110 | unsigned i_blkbits = READ_ONCE(inode->i_blkbits); |
| 1111 | unsigned blkbits = i_blkbits; |
| 1112 | unsigned blocksize_mask = (1 << blkbits) - 1; |
| 1113 | ssize_t retval = -EINVAL; |
| 1114 | const size_t count = iov_iter_count(iter); |
| 1115 | loff_t offset = iocb->ki_pos; |
| 1116 | const loff_t end = offset + count; |
| 1117 | struct dio *dio; |
| 1118 | struct dio_submit sdio = { NULL, }; |
| 1119 | struct buffer_head map_bh = { 0, }; |
| 1120 | struct blk_plug plug; |
| 1121 | unsigned long align = offset | iov_iter_alignment(iter); |
| 1122 | |
| 1123 | /* watch out for a 0 len io from a tricksy fs */ |
| 1124 | if (iov_iter_rw(iter) == READ && !count) |
| 1125 | return 0; |
| 1126 | |
| 1127 | dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); |
| 1128 | if (!dio) |
| 1129 | return -ENOMEM; |
| 1130 | /* |
| 1131 | * Believe it or not, zeroing out the page array caused a .5% |
| 1132 | * performance regression in a database benchmark. So, we take |
| 1133 | * care to only zero out what's needed. |
| 1134 | */ |
| 1135 | memset(dio, 0, offsetof(struct dio, pages)); |
| 1136 | |
| 1137 | dio->flags = flags; |
| 1138 | if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { |
| 1139 | /* will be released by direct_io_worker */ |
| 1140 | inode_lock(inode); |
| 1141 | } |
| 1142 | dio->is_pinned = iov_iter_extract_will_pin(iter); |
| 1143 | |
| 1144 | /* Once we sampled i_size check for reads beyond EOF */ |
| 1145 | dio->i_size = i_size_read(inode); |
| 1146 | if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { |
| 1147 | retval = 0; |
| 1148 | goto fail_dio; |
| 1149 | } |
| 1150 | |
| 1151 | if (align & blocksize_mask) { |
| 1152 | if (bdev) |
| 1153 | blkbits = blksize_bits(bdev_logical_block_size(bdev)); |
| 1154 | blocksize_mask = (1 << blkbits) - 1; |
| 1155 | if (align & blocksize_mask) |
| 1156 | goto fail_dio; |
| 1157 | } |
| 1158 | |
| 1159 | if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) { |
| 1160 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
| 1161 | |
| 1162 | retval = filemap_write_and_wait_range(mapping, offset, end - 1); |
| 1163 | if (retval) |
| 1164 | goto fail_dio; |
| 1165 | } |
| 1166 | |
| 1167 | /* |
| 1168 | * For file extending writes updating i_size before data writeouts |
| 1169 | * complete can expose uninitialized blocks in dumb filesystems. |
| 1170 | * In that case we need to wait for I/O completion even if asked |
| 1171 | * for an asynchronous write. |
| 1172 | */ |
| 1173 | if (is_sync_kiocb(iocb)) |
| 1174 | dio->is_async = false; |
| 1175 | else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode)) |
| 1176 | dio->is_async = false; |
| 1177 | else |
| 1178 | dio->is_async = true; |
| 1179 | |
| 1180 | dio->inode = inode; |
| 1181 | if (iov_iter_rw(iter) == WRITE) { |
| 1182 | dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; |
| 1183 | if (iocb->ki_flags & IOCB_NOWAIT) |
| 1184 | dio->opf |= REQ_NOWAIT; |
| 1185 | } else { |
| 1186 | dio->opf = REQ_OP_READ; |
| 1187 | } |
| 1188 | |
| 1189 | /* |
| 1190 | * For AIO O_(D)SYNC writes we need to defer completions to a workqueue |
| 1191 | * so that we can call ->fsync. |
| 1192 | */ |
| 1193 | if (dio->is_async && iov_iter_rw(iter) == WRITE) { |
| 1194 | retval = 0; |
| 1195 | if (iocb_is_dsync(iocb)) |
| 1196 | retval = dio_set_defer_completion(dio); |
| 1197 | else if (!dio->inode->i_sb->s_dio_done_wq) { |
| 1198 | /* |
| 1199 | * In case of AIO write racing with buffered read we |
| 1200 | * need to defer completion. We can't decide this now, |
| 1201 | * however the workqueue needs to be initialized here. |
| 1202 | */ |
| 1203 | retval = sb_init_dio_done_wq(dio->inode->i_sb); |
| 1204 | } |
| 1205 | if (retval) |
| 1206 | goto fail_dio; |
| 1207 | } |
| 1208 | |
| 1209 | /* |
| 1210 | * Will be decremented at I/O completion time. |
| 1211 | */ |
| 1212 | inode_dio_begin(inode); |
| 1213 | |
| 1214 | sdio.blkbits = blkbits; |
| 1215 | sdio.blkfactor = i_blkbits - blkbits; |
| 1216 | sdio.block_in_file = offset >> blkbits; |
| 1217 | |
| 1218 | sdio.get_block = get_block; |
| 1219 | dio->end_io = end_io; |
| 1220 | sdio.final_block_in_bio = -1; |
| 1221 | sdio.next_block_for_io = -1; |
| 1222 | |
| 1223 | dio->iocb = iocb; |
| 1224 | |
| 1225 | spin_lock_init(&dio->bio_lock); |
| 1226 | dio->refcount = 1; |
| 1227 | |
| 1228 | dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ; |
| 1229 | sdio.iter = iter; |
| 1230 | sdio.final_block_in_request = end >> blkbits; |
| 1231 | |
| 1232 | /* |
| 1233 | * In case of non-aligned buffers, we may need 2 more |
| 1234 | * pages since we need to zero out first and last block. |
| 1235 | */ |
| 1236 | if (unlikely(sdio.blkfactor)) |
| 1237 | sdio.pages_in_io = 2; |
| 1238 | |
| 1239 | sdio.pages_in_io += iov_iter_npages(iter, INT_MAX); |
| 1240 | |
| 1241 | blk_start_plug(&plug); |
| 1242 | |
| 1243 | retval = do_direct_IO(dio, &sdio, &map_bh); |
| 1244 | if (retval) |
| 1245 | dio_cleanup(dio, &sdio); |
| 1246 | |
| 1247 | if (retval == -ENOTBLK) { |
| 1248 | /* |
| 1249 | * The remaining part of the request will be |
| 1250 | * handled by buffered I/O when we return |
| 1251 | */ |
| 1252 | retval = 0; |
| 1253 | } |
| 1254 | /* |
| 1255 | * There may be some unwritten disk at the end of a part-written |
| 1256 | * fs-block-sized block. Go zero that now. |
| 1257 | */ |
| 1258 | dio_zero_block(dio, &sdio, 1, &map_bh); |
| 1259 | |
| 1260 | if (sdio.cur_page) { |
| 1261 | ssize_t ret2; |
| 1262 | |
| 1263 | ret2 = dio_send_cur_page(dio, &sdio, &map_bh); |
| 1264 | if (retval == 0) |
| 1265 | retval = ret2; |
| 1266 | dio_unpin_page(dio, sdio.cur_page); |
| 1267 | sdio.cur_page = NULL; |
| 1268 | } |
| 1269 | if (sdio.bio) |
| 1270 | dio_bio_submit(dio, &sdio); |
| 1271 | |
| 1272 | blk_finish_plug(&plug); |
| 1273 | |
| 1274 | /* |
| 1275 | * It is possible that, we return short IO due to end of file. |
| 1276 | * In that case, we need to release all the pages we got hold on. |
| 1277 | */ |
| 1278 | dio_cleanup(dio, &sdio); |
| 1279 | |
| 1280 | /* |
| 1281 | * All block lookups have been performed. For READ requests |
| 1282 | * we can let i_mutex go now that its achieved its purpose |
| 1283 | * of protecting us from looking up uninitialized blocks. |
| 1284 | */ |
| 1285 | if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING)) |
| 1286 | inode_unlock(dio->inode); |
| 1287 | |
| 1288 | /* |
| 1289 | * The only time we want to leave bios in flight is when a successful |
| 1290 | * partial aio read or full aio write have been setup. In that case |
| 1291 | * bio completion will call aio_complete. The only time it's safe to |
| 1292 | * call aio_complete is when we return -EIOCBQUEUED, so we key on that. |
| 1293 | * This had *better* be the only place that raises -EIOCBQUEUED. |
| 1294 | */ |
| 1295 | BUG_ON(retval == -EIOCBQUEUED); |
| 1296 | if (dio->is_async && retval == 0 && dio->result && |
| 1297 | (iov_iter_rw(iter) == READ || dio->result == count)) |
| 1298 | retval = -EIOCBQUEUED; |
| 1299 | else |
| 1300 | dio_await_completion(dio); |
| 1301 | |
| 1302 | if (drop_refcount(dio) == 0) { |
| 1303 | retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE); |
| 1304 | } else |
| 1305 | BUG_ON(retval != -EIOCBQUEUED); |
| 1306 | |
| 1307 | return retval; |
| 1308 | |
| 1309 | fail_dio: |
| 1310 | if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) |
| 1311 | inode_unlock(inode); |
| 1312 | |
| 1313 | kmem_cache_free(dio_cache, dio); |
| 1314 | return retval; |
| 1315 | } |
| 1316 | EXPORT_SYMBOL(__blockdev_direct_IO); |
| 1317 | |
| 1318 | static __init int dio_init(void) |
| 1319 | { |
| 1320 | dio_cache = KMEM_CACHE(dio, SLAB_PANIC); |
| 1321 | return 0; |
| 1322 | } |
| 1323 | module_init(dio_init) |