fs/iomap/direct-io.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2010 Red Hat, Inc.
   4  * Copyright (c) 2016-2018 Christoph Hellwig.
   5  */
   6 #include <linux/module.h>
   7 #include <linux/compiler.h>
   8 #include <linux/fs.h>
   9 #include <linux/iomap.h>
  10 #include <linux/backing-dev.h>
  11 #include <linux/uio.h>
  12 #include <linux/task_io_accounting_ops.h>
  13
  14 #include "../internal.h"
  15
  16 /*
  17  * Private flags for iomap_dio, must not overlap with the public ones in
  18  * iomap.h:
  19  */
  20 #define IOMAP_DIO_WRITE_FUA     (1 << 28)
  21 #define IOMAP_DIO_NEED_SYNC     (1 << 29)
  22 #define IOMAP_DIO_WRITE         (1 << 30)
  23 #define IOMAP_DIO_DIRTY         (1 << 31)
  24
  25 struct iomap_dio {
  26         struct kiocb            *iocb;
  27         iomap_dio_end_io_t      *end_io;
  28         loff_t                  i_size;
  29         loff_t                  size;
  30         atomic_t                ref;
  31         unsigned                flags;
  32         int                     error;
  33         bool                    wait_for_completion;
  34
  35         union {
  36                 /* used during submission and for synchronous completion: */
  37                 struct {
  38                         struct iov_iter         *iter;
  39                         struct task_struct      *waiter;
  40                         struct request_queue    *last_queue;
  41                         blk_qc_t                cookie;
  42                 } submit;
  43
  44                 /* used for aio completion: */
  45                 struct {
  46                         struct work_struct      work;
  47                 } aio;
  48         };
  49 };
  50
  51 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
  52 {
  53         struct request_queue *q = READ_ONCE(kiocb->private);
  54
  55         if (!q)
  56                 return 0;
  57         return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
  58 }
  59 EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
  60
  61 static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
  62                 struct bio *bio)
  63 {
  64         atomic_inc(&dio->ref);
  65
  66         if (dio->iocb->ki_flags & IOCB_HIPRI)
  67                 bio_set_polled(bio, dio->iocb);
  68
  69         dio->submit.last_queue = bdev_get_queue(iomap->bdev);
  70         dio->submit.cookie = submit_bio(bio);
  71 }
  72
  73 static ssize_t iomap_dio_complete(struct iomap_dio *dio)
  74 {
  75         struct kiocb *iocb = dio->iocb;
  76         struct inode *inode = file_inode(iocb->ki_filp);
  77         loff_t offset = iocb->ki_pos;
  78         ssize_t ret;
  79
  80         if (dio->end_io) {
  81                 ret = dio->end_io(iocb,
  82                                 dio->error ? dio->error : dio->size,
  83                                 dio->flags);
  84         } else {
  85                 ret = dio->error;
  86         }
  87
  88         if (likely(!ret)) {
  89                 ret = dio->size;
  90                 /* check for short read */
  91                 if (offset + ret > dio->i_size &&
  92                     !(dio->flags & IOMAP_DIO_WRITE))
  93                         ret = dio->i_size - offset;
  94                 iocb->ki_pos += ret;
  95         }
  96
  97         /*
  98          * Try again to invalidate clean pages which might have been cached by
  99          * non-direct readahead, or faulted in by get_user_pages() if the source
 100          * of the write was an mmap'ed region of the file we're writing.  Either
 101          * one is a pretty crazy thing to do, so we don't support it 100%.  If
 102          * this invalidation fails, tough, the write still worked...
 103          *
 104          * And this page cache invalidation has to be after dio->end_io(), as
 105          * some filesystems convert unwritten extents to real allocations in
 106          * end_io() when necessary, otherwise a racing buffer read would cache
 107          * zeros from unwritten extents.
 108          */
 109         if (!dio->error &&
 110             (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
 111                 int err;
 112                 err = invalidate_inode_pages2_range(inode->i_mapping,
 113                                 offset >> PAGE_SHIFT,
 114                                 (offset + dio->size - 1) >> PAGE_SHIFT);
 115                 if (err)
 116                         dio_warn_stale_pagecache(iocb->ki_filp);
 117         }
 118
 119         /*
 120          * If this is a DSYNC write, make sure we push it to stable storage now
 121          * that we've written data.
 122          */
 123         if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
 124                 ret = generic_write_sync(iocb, ret);
 125
 126         inode_dio_end(file_inode(iocb->ki_filp));
 127         kfree(dio);
 128
 129         return ret;
 130 }
 131
 132 static void iomap_dio_complete_work(struct work_struct *work)
 133 {
 134         struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
 135         struct kiocb *iocb = dio->iocb;
 136
 137         iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
 138 }
 139
 140 /*
 141  * Set an error in the dio if none is set yet.  We have to use cmpxchg
 142  * as the submission context and the completion context(s) can race to
 143  * update the error.
 144  */
 145 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
 146 {
 147         cmpxchg(&dio->error, 0, ret);
 148 }
 149
 150 static void iomap_dio_bio_end_io(struct bio *bio)
 151 {
 152         struct iomap_dio *dio = bio->bi_private;
 153         bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
 154
 155         if (bio->bi_status)
 156                 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
 157
 158         if (atomic_dec_and_test(&dio->ref)) {
 159                 if (dio->wait_for_completion) {
 160                         struct task_struct *waiter = dio->submit.waiter;
 161                         WRITE_ONCE(dio->submit.waiter, NULL);
 162                         blk_wake_io_task(waiter);
 163                 } else if (dio->flags & IOMAP_DIO_WRITE) {
 164                         struct inode *inode = file_inode(dio->iocb->ki_filp);
 165
 166                         INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
 167                         queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
 168                 } else {
 169                         iomap_dio_complete_work(&dio->aio.work);
 170                 }
 171         }
 172
 173         if (should_dirty) {
 174                 bio_check_pages_dirty(bio);
 175         } else {
 176                 bio_release_pages(bio, false);
 177                 bio_put(bio);
 178         }
 179 }
 180
 181 static void
 182 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 183                 unsigned len)
 184 {
 185         struct page *page = ZERO_PAGE(0);
 186         int flags = REQ_SYNC | REQ_IDLE;
 187         struct bio *bio;
 188
 189         bio = bio_alloc(GFP_KERNEL, 1);
 190         bio_set_dev(bio, iomap->bdev);
 191         bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 192         bio->bi_private = dio;
 193         bio->bi_end_io = iomap_dio_bio_end_io;
 194
 195         get_page(page);
 196         __bio_add_page(bio, page, len, 0);
 197         bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
 198         iomap_dio_submit_bio(dio, iomap, bio);
 199 }
 200
 201 static loff_t
 202 iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
 203                 struct iomap_dio *dio, struct iomap *iomap)
 204 {
 205         unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
 206         unsigned int fs_block_size = i_blocksize(inode), pad;
 207         unsigned int align = iov_iter_alignment(dio->submit.iter);
 208         struct iov_iter iter;
 209         struct bio *bio;
 210         bool need_zeroout = false;
 211         bool use_fua = false;
 212         int nr_pages, ret = 0;
 213         size_t copied = 0;
 214
 215         if ((pos | length | align) & ((1 << blkbits) - 1))
 216                 return -EINVAL;
 217
 218         if (iomap->type == IOMAP_UNWRITTEN) {
 219                 dio->flags |= IOMAP_DIO_UNWRITTEN;
 220                 need_zeroout = true;
 221         }
 222
 223         if (iomap->flags & IOMAP_F_SHARED)
 224                 dio->flags |= IOMAP_DIO_COW;
 225
 226         if (iomap->flags & IOMAP_F_NEW) {
 227                 need_zeroout = true;
 228         } else if (iomap->type == IOMAP_MAPPED) {
 229                 /*
 230                  * Use a FUA write if we need datasync semantics, this is a pure
 231                  * data IO that doesn't require any metadata updates (including
 232                  * after IO completion such as unwritten extent conversion) and
 233                  * the underlying device supports FUA. This allows us to avoid
 234                  * cache flushes on IO completion.
 235                  */
 236                 if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
 237                     (dio->flags & IOMAP_DIO_WRITE_FUA) &&
 238                     blk_queue_fua(bdev_get_queue(iomap->bdev)))
 239                         use_fua = true;
 240         }
 241
 242         /*
 243          * Operate on a partial iter trimmed to the extent we were called for.
 244          * We'll update the iter in the dio once we're done with this extent.
 245          */
 246         iter = *dio->submit.iter;
 247         iov_iter_truncate(&iter, length);
 248
 249         nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
 250         if (nr_pages <= 0)
 251                 return nr_pages;
 252
 253         if (need_zeroout) {
 254                 /* zero out from the start of the block to the write offset */
 255                 pad = pos & (fs_block_size - 1);
 256                 if (pad)
 257                         iomap_dio_zero(dio, iomap, pos - pad, pad);
 258         }
 259
 260         do {
 261                 size_t n;
 262                 if (dio->error) {
 263                         iov_iter_revert(dio->submit.iter, copied);
 264                         return 0;
 265                 }
 266
 267                 bio = bio_alloc(GFP_KERNEL, nr_pages);
 268                 bio_set_dev(bio, iomap->bdev);
 269                 bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 270                 bio->bi_write_hint = dio->iocb->ki_hint;
 271                 bio->bi_ioprio = dio->iocb->ki_ioprio;
 272                 bio->bi_private = dio;
 273                 bio->bi_end_io = iomap_dio_bio_end_io;
 274
 275                 ret = bio_iov_iter_get_pages(bio, &iter);
 276                 if (unlikely(ret)) {
 277                         /*
 278                          * We have to stop part way through an IO. We must fall
 279                          * through to the sub-block tail zeroing here, otherwise
 280                          * this short IO may expose stale data in the tail of
 281                          * the block we haven't written data to.
 282                          */
 283                         bio_put(bio);
 284                         goto zero_tail;
 285                 }
 286
 287                 n = bio->bi_iter.bi_size;
 288                 if (dio->flags & IOMAP_DIO_WRITE) {
 289                         bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
 290                         if (use_fua)
 291                                 bio->bi_opf |= REQ_FUA;
 292                         else
 293                                 dio->flags &= ~IOMAP_DIO_WRITE_FUA;
 294                         task_io_account_write(n);
 295                 } else {
 296                         bio->bi_opf = REQ_OP_READ;
 297                         if (dio->flags & IOMAP_DIO_DIRTY)
 298                                 bio_set_pages_dirty(bio);
 299                 }
 300
 301                 iov_iter_advance(dio->submit.iter, n);
 302
 303                 dio->size += n;
 304                 pos += n;
 305                 copied += n;
 306
 307                 nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
 308                 iomap_dio_submit_bio(dio, iomap, bio);
 309         } while (nr_pages);
 310
 311         /*
 312          * We need to zeroout the tail of a sub-block write if the extent type
 313          * requires zeroing or the write extends beyond EOF. If we don't zero
 314          * the block tail in the latter case, we can expose stale data via mmap
 315          * reads of the EOF block.
 316          */
 317 zero_tail:
 318         if (need_zeroout ||
 319             ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
 320                 /* zero out from the end of the write to the end of the block */
 321                 pad = pos & (fs_block_size - 1);
 322                 if (pad)
 323                         iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
 324         }
 325         return copied ? copied : ret;
 326 }
 327
 328 static loff_t
 329 iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
 330 {
 331         length = iov_iter_zero(length, dio->submit.iter);
 332         dio->size += length;
 333         return length;
 334 }
 335
 336 static loff_t
 337 iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
 338                 struct iomap_dio *dio, struct iomap *iomap)
 339 {
 340         struct iov_iter *iter = dio->submit.iter;
 341         size_t copied;
 342
 343         BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
 344
 345         if (dio->flags & IOMAP_DIO_WRITE) {
 346                 loff_t size = inode->i_size;
 347
 348                 if (pos > size)
 349                         memset(iomap->inline_data + size, 0, pos - size);
 350                 copied = copy_from_iter(iomap->inline_data + pos, length, iter);
 351                 if (copied) {
 352                         if (pos + copied > size)
 353                                 i_size_write(inode, pos + copied);
 354                         mark_inode_dirty(inode);
 355                 }
 356         } else {
 357                 copied = copy_to_iter(iomap->inline_data + pos, length, iter);
 358         }
 359         dio->size += copied;
 360         return copied;
 361 }
 362
 363 static loff_t
 364 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 365                 void *data, struct iomap *iomap)
 366 {
 367         struct iomap_dio *dio = data;
 368
 369         switch (iomap->type) {
 370         case IOMAP_HOLE:
 371                 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
 372                         return -EIO;
 373                 return iomap_dio_hole_actor(length, dio);
 374         case IOMAP_UNWRITTEN:
 375                 if (!(dio->flags & IOMAP_DIO_WRITE))
 376                         return iomap_dio_hole_actor(length, dio);
 377                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 378         case IOMAP_MAPPED:
 379                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 380         case IOMAP_INLINE:
 381                 return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
 382         default:
 383                 WARN_ON_ONCE(1);
 384                 return -EIO;
 385         }
 386 }
 387
 388 /*
 389  * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
 390  * is being issued as AIO or not.  This allows us to optimise pure data writes
 391  * to use REQ_FUA rather than requiring generic_write_sync() to issue a
 392  * REQ_FLUSH post write. This is slightly tricky because a single request here
 393  * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
 394  * may be pure data writes. In that case, we still need to do a full data sync
 395  * completion.
 396  */
 397 ssize_t
 398 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 399                 const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
 400 {
 401         struct address_space *mapping = iocb->ki_filp->f_mapping;
 402         struct inode *inode = file_inode(iocb->ki_filp);
 403         size_t count = iov_iter_count(iter);
 404         loff_t pos = iocb->ki_pos, start = pos;
 405         loff_t end = iocb->ki_pos + count - 1, ret = 0;
 406         unsigned int flags = IOMAP_DIRECT;
 407         bool wait_for_completion = is_sync_kiocb(iocb);
 408         struct blk_plug plug;
 409         struct iomap_dio *dio;
 410
 411         lockdep_assert_held(&inode->i_rwsem);
 412
 413         if (!count)
 414                 return 0;
 415
 416         dio = kmalloc(sizeof(*dio), GFP_KERNEL);
 417         if (!dio)
 418                 return -ENOMEM;
 419
 420         dio->iocb = iocb;
 421         atomic_set(&dio->ref, 1);
 422         dio->size = 0;
 423         dio->i_size = i_size_read(inode);
 424         dio->end_io = end_io;
 425         dio->error = 0;
 426         dio->flags = 0;
 427
 428         dio->submit.iter = iter;
 429         dio->submit.waiter = current;
 430         dio->submit.cookie = BLK_QC_T_NONE;
 431         dio->submit.last_queue = NULL;
 432
 433         if (iov_iter_rw(iter) == READ) {
 434                 if (pos >= dio->i_size)
 435                         goto out_free_dio;
 436
 437                 if (iter_is_iovec(iter) && iov_iter_rw(iter) == READ)
 438                         dio->flags |= IOMAP_DIO_DIRTY;
 439         } else {
 440                 flags |= IOMAP_WRITE;
 441                 dio->flags |= IOMAP_DIO_WRITE;
 442
 443                 /* for data sync or sync, we need sync completion processing */
 444                 if (iocb->ki_flags & IOCB_DSYNC)
 445                         dio->flags |= IOMAP_DIO_NEED_SYNC;
 446
 447                 /*
 448                  * For datasync only writes, we optimistically try using FUA for
 449                  * this IO.  Any non-FUA write that occurs will clear this flag,
 450                  * hence we know before completion whether a cache flush is
 451                  * necessary.
 452                  */
 453                 if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
 454                         dio->flags |= IOMAP_DIO_WRITE_FUA;
 455         }
 456
 457         if (iocb->ki_flags & IOCB_NOWAIT) {
 458                 if (filemap_range_has_page(mapping, start, end)) {
 459                         ret = -EAGAIN;
 460                         goto out_free_dio;
 461                 }
 462                 flags |= IOMAP_NOWAIT;
 463         }
 464
 465         ret = filemap_write_and_wait_range(mapping, start, end);
 466         if (ret)
 467                 goto out_free_dio;
 468
 469         /*
 470          * Try to invalidate cache pages for the range we're direct
 471          * writing.  If this invalidation fails, tough, the write will
 472          * still work, but racing two incompatible write paths is a
 473          * pretty crazy thing to do, so we don't support it 100%.
 474          */
 475         ret = invalidate_inode_pages2_range(mapping,
 476                         start >> PAGE_SHIFT, end >> PAGE_SHIFT);
 477         if (ret)
 478                 dio_warn_stale_pagecache(iocb->ki_filp);
 479         ret = 0;
 480
 481         if (iov_iter_rw(iter) == WRITE && !wait_for_completion &&
 482             !inode->i_sb->s_dio_done_wq) {
 483                 ret = sb_init_dio_done_wq(inode->i_sb);
 484                 if (ret < 0)
 485                         goto out_free_dio;
 486         }
 487
 488         inode_dio_begin(inode);
 489
 490         blk_start_plug(&plug);
 491         do {
 492                 ret = iomap_apply(inode, pos, count, flags, ops, dio,
 493                                 iomap_dio_actor);
 494                 if (ret <= 0) {
 495                         /* magic error code to fall back to buffered I/O */
 496                         if (ret == -ENOTBLK) {
 497                                 wait_for_completion = true;
 498                                 ret = 0;
 499                         }
 500                         break;
 501                 }
 502                 pos += ret;
 503
 504                 if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
 505                         break;
 506         } while ((count = iov_iter_count(iter)) > 0);
 507         blk_finish_plug(&plug);
 508
 509         if (ret < 0)
 510                 iomap_dio_set_error(dio, ret);
 511
 512         /*
 513          * If all the writes we issued were FUA, we don't need to flush the
 514          * cache on IO completion. Clear the sync flag for this case.
 515          */
 516         if (dio->flags & IOMAP_DIO_WRITE_FUA)
 517                 dio->flags &= ~IOMAP_DIO_NEED_SYNC;
 518
 519         WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
 520         WRITE_ONCE(iocb->private, dio->submit.last_queue);
 521
 522         /*
 523          * We are about to drop our additional submission reference, which
 524          * might be the last reference to the dio.  There are three three
 525          * different ways we can progress here:
 526          *
 527          *  (a) If this is the last reference we will always complete and free
 528          *      the dio ourselves.
 529          *  (b) If this is not the last reference, and we serve an asynchronous
 530          *      iocb, we must never touch the dio after the decrement, the
 531          *      I/O completion handler will complete and free it.
 532          *  (c) If this is not the last reference, but we serve a synchronous
 533          *      iocb, the I/O completion handler will wake us up on the drop
 534          *      of the final reference, and we will complete and free it here
 535          *      after we got woken by the I/O completion handler.
 536          */
 537         dio->wait_for_completion = wait_for_completion;
 538         if (!atomic_dec_and_test(&dio->ref)) {
 539                 if (!wait_for_completion)
 540                         return -EIOCBQUEUED;
 541
 542                 for (;;) {
 543                         set_current_state(TASK_UNINTERRUPTIBLE);
 544                         if (!READ_ONCE(dio->submit.waiter))
 545                                 break;
 546
 547                         if (!(iocb->ki_flags & IOCB_HIPRI) ||
 548                             !dio->submit.last_queue ||
 549                             !blk_poll(dio->submit.last_queue,
 550                                          dio->submit.cookie, true))
 551                                 io_schedule();
 552                 }
 553                 __set_current_state(TASK_RUNNING);
 554         }
 555
 556         return iomap_dio_complete(dio);
 557
 558 out_free_dio:
 559         kfree(dio);
 560         return ret;
 561 }
 562 EXPORT_SYMBOL_GPL(iomap_dio_rw);