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 #include "trace.h"
  14
  15 #include "../internal.h"
  16
  17 /*
  18  * Private flags for iomap_dio, must not overlap with the public ones in
  19  * iomap.h:
  20  */
  21 #define IOMAP_DIO_WRITE_FUA     (1 << 28)
  22 #define IOMAP_DIO_NEED_SYNC     (1 << 29)
  23 #define IOMAP_DIO_WRITE         (1 << 30)
  24 #define IOMAP_DIO_DIRTY         (1 << 31)
  25
  26 struct iomap_dio {
  27         struct kiocb            *iocb;
  28         const struct iomap_dio_ops *dops;
  29         loff_t                  i_size;
  30         loff_t                  size;
  31         atomic_t                ref;
  32         unsigned                flags;
  33         int                     error;
  34         bool                    wait_for_completion;
  35
  36         union {
  37                 /* used during submission and for synchronous completion: */
  38                 struct {
  39                         struct iov_iter         *iter;
  40                         struct task_struct      *waiter;
  41                         struct request_queue    *last_queue;
  42                         blk_qc_t                cookie;
  43                 } submit;
  44
  45                 /* used for aio completion: */
  46                 struct {
  47                         struct work_struct      work;
  48                 } aio;
  49         };
  50 };
  51
  52 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
  53 {
  54         struct request_queue *q = READ_ONCE(kiocb->private);
  55
  56         if (!q)
  57                 return 0;
  58         return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
  59 }
  60 EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
  61
  62 static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
  63                 struct bio *bio, loff_t pos)
  64 {
  65         atomic_inc(&dio->ref);
  66
  67         if (dio->iocb->ki_flags & IOCB_HIPRI)
  68                 bio_set_polled(bio, dio->iocb);
  69
  70         dio->submit.last_queue = bdev_get_queue(iomap->bdev);
  71         if (dio->dops && dio->dops->submit_io)
  72                 dio->submit.cookie = dio->dops->submit_io(
  73                                 file_inode(dio->iocb->ki_filp),
  74                                 iomap, bio, pos);
  75         else
  76                 dio->submit.cookie = submit_bio(bio);
  77 }
  78
  79 static ssize_t iomap_dio_complete(struct iomap_dio *dio)
  80 {
  81         const struct iomap_dio_ops *dops = dio->dops;
  82         struct kiocb *iocb = dio->iocb;
  83         struct inode *inode = file_inode(iocb->ki_filp);
  84         loff_t offset = iocb->ki_pos;
  85         ssize_t ret = dio->error;
  86
  87         if (dops && dops->end_io)
  88                 ret = dops->end_io(iocb, dio->size, ret, dio->flags);
  89
  90         if (likely(!ret)) {
  91                 ret = dio->size;
  92                 /* check for short read */
  93                 if (offset + ret > dio->i_size &&
  94                     !(dio->flags & IOMAP_DIO_WRITE))
  95                         ret = dio->i_size - offset;
  96                 iocb->ki_pos += ret;
  97         }
  98
  99         /*
 100          * Try again to invalidate clean pages which might have been cached by
 101          * non-direct readahead, or faulted in by get_user_pages() if the source
 102          * of the write was an mmap'ed region of the file we're writing.  Either
 103          * one is a pretty crazy thing to do, so we don't support it 100%.  If
 104          * this invalidation fails, tough, the write still worked...
 105          *
 106          * And this page cache invalidation has to be after ->end_io(), as some
 107          * filesystems convert unwritten extents to real allocations in
 108          * ->end_io() when necessary, otherwise a racing buffer read would cache
 109          * zeros from unwritten extents.
 110          */
 111         if (!dio->error &&
 112             (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
 113                 int err;
 114                 err = invalidate_inode_pages2_range(inode->i_mapping,
 115                                 offset >> PAGE_SHIFT,
 116                                 (offset + dio->size - 1) >> PAGE_SHIFT);
 117                 if (err)
 118                         dio_warn_stale_pagecache(iocb->ki_filp);
 119         }
 120
 121         /*
 122          * If this is a DSYNC write, make sure we push it to stable storage now
 123          * that we've written data.
 124          */
 125         if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
 126                 ret = generic_write_sync(iocb, ret);
 127
 128         inode_dio_end(file_inode(iocb->ki_filp));
 129         kfree(dio);
 130
 131         return ret;
 132 }
 133
 134 static void iomap_dio_complete_work(struct work_struct *work)
 135 {
 136         struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
 137         struct kiocb *iocb = dio->iocb;
 138
 139         iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
 140 }
 141
 142 /*
 143  * Set an error in the dio if none is set yet.  We have to use cmpxchg
 144  * as the submission context and the completion context(s) can race to
 145  * update the error.
 146  */
 147 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
 148 {
 149         cmpxchg(&dio->error, 0, ret);
 150 }
 151
 152 static void iomap_dio_bio_end_io(struct bio *bio)
 153 {
 154         struct iomap_dio *dio = bio->bi_private;
 155         bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
 156
 157         if (bio->bi_status)
 158                 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
 159
 160         if (atomic_dec_and_test(&dio->ref)) {
 161                 if (dio->wait_for_completion) {
 162                         struct task_struct *waiter = dio->submit.waiter;
 163                         WRITE_ONCE(dio->submit.waiter, NULL);
 164                         blk_wake_io_task(waiter);
 165                 } else if (dio->flags & IOMAP_DIO_WRITE) {
 166                         struct inode *inode = file_inode(dio->iocb->ki_filp);
 167
 168                         INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
 169                         queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
 170                 } else {
 171                         iomap_dio_complete_work(&dio->aio.work);
 172                 }
 173         }
 174
 175         if (should_dirty) {
 176                 bio_check_pages_dirty(bio);
 177         } else {
 178                 bio_release_pages(bio, false);
 179                 bio_put(bio);
 180         }
 181 }
 182
 183 static void
 184 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 185                 unsigned len)
 186 {
 187         struct page *page = ZERO_PAGE(0);
 188         int flags = REQ_SYNC | REQ_IDLE;
 189         struct bio *bio;
 190
 191         bio = bio_alloc(GFP_KERNEL, 1);
 192         bio_set_dev(bio, iomap->bdev);
 193         bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 194         bio->bi_private = dio;
 195         bio->bi_end_io = iomap_dio_bio_end_io;
 196
 197         get_page(page);
 198         __bio_add_page(bio, page, len, 0);
 199         bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
 200         iomap_dio_submit_bio(dio, iomap, bio, pos);
 201 }
 202
 203 static loff_t
 204 iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
 205                 struct iomap_dio *dio, struct iomap *iomap)
 206 {
 207         unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
 208         unsigned int fs_block_size = i_blocksize(inode), pad;
 209         unsigned int align = iov_iter_alignment(dio->submit.iter);
 210         struct bio *bio;
 211         bool need_zeroout = false;
 212         bool use_fua = false;
 213         int nr_pages, ret = 0;
 214         size_t copied = 0;
 215         size_t orig_count;
 216
 217         if ((pos | length | align) & ((1 << blkbits) - 1))
 218                 return -EINVAL;
 219
 220         if (iomap->type == IOMAP_UNWRITTEN) {
 221                 dio->flags |= IOMAP_DIO_UNWRITTEN;
 222                 need_zeroout = true;
 223         }
 224
 225         if (iomap->flags & IOMAP_F_SHARED)
 226                 dio->flags |= IOMAP_DIO_COW;
 227
 228         if (iomap->flags & IOMAP_F_NEW) {
 229                 need_zeroout = true;
 230         } else if (iomap->type == IOMAP_MAPPED) {
 231                 /*
 232                  * Use a FUA write if we need datasync semantics, this is a pure
 233                  * data IO that doesn't require any metadata updates (including
 234                  * after IO completion such as unwritten extent conversion) and
 235                  * the underlying device supports FUA. This allows us to avoid
 236                  * cache flushes on IO completion.
 237                  */
 238                 if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
 239                     (dio->flags & IOMAP_DIO_WRITE_FUA) &&
 240                     blk_queue_fua(bdev_get_queue(iomap->bdev)))
 241                         use_fua = true;
 242         }
 243
 244         /*
 245          * Save the original count and trim the iter to just the extent we
 246          * are operating on right now.  The iter will be re-expanded once
 247          * we are done.
 248          */
 249         orig_count = iov_iter_count(dio->submit.iter);
 250         iov_iter_truncate(dio->submit.iter, length);
 251
 252         nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
 253         if (nr_pages <= 0) {
 254                 ret = nr_pages;
 255                 goto out;
 256         }
 257
 258         if (need_zeroout) {
 259                 /* zero out from the start of the block to the write offset */
 260                 pad = pos & (fs_block_size - 1);
 261                 if (pad)
 262                         iomap_dio_zero(dio, iomap, pos - pad, pad);
 263         }
 264
 265         do {
 266                 size_t n;
 267                 if (dio->error) {
 268                         iov_iter_revert(dio->submit.iter, copied);
 269                         copied = ret = 0;
 270                         goto out;
 271                 }
 272
 273                 bio = bio_alloc(GFP_KERNEL, nr_pages);
 274                 bio_set_dev(bio, iomap->bdev);
 275                 bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 276                 bio->bi_write_hint = dio->iocb->ki_hint;
 277                 bio->bi_ioprio = dio->iocb->ki_ioprio;
 278                 bio->bi_private = dio;
 279                 bio->bi_end_io = iomap_dio_bio_end_io;
 280
 281                 ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
 282                 if (unlikely(ret)) {
 283                         /*
 284                          * We have to stop part way through an IO. We must fall
 285                          * through to the sub-block tail zeroing here, otherwise
 286                          * this short IO may expose stale data in the tail of
 287                          * the block we haven't written data to.
 288                          */
 289                         bio_put(bio);
 290                         goto zero_tail;
 291                 }
 292
 293                 n = bio->bi_iter.bi_size;
 294                 if (dio->flags & IOMAP_DIO_WRITE) {
 295                         bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
 296                         if (use_fua)
 297                                 bio->bi_opf |= REQ_FUA;
 298                         else
 299                                 dio->flags &= ~IOMAP_DIO_WRITE_FUA;
 300                         task_io_account_write(n);
 301                 } else {
 302                         bio->bi_opf = REQ_OP_READ;
 303                         if (dio->flags & IOMAP_DIO_DIRTY)
 304                                 bio_set_pages_dirty(bio);
 305                 }
 306
 307                 dio->size += n;
 308                 copied += n;
 309
 310                 nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
 311                 iomap_dio_submit_bio(dio, iomap, bio, pos);
 312                 pos += n;
 313         } while (nr_pages);
 314
 315         /*
 316          * We need to zeroout the tail of a sub-block write if the extent type
 317          * requires zeroing or the write extends beyond EOF. If we don't zero
 318          * the block tail in the latter case, we can expose stale data via mmap
 319          * reads of the EOF block.
 320          */
 321 zero_tail:
 322         if (need_zeroout ||
 323             ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
 324                 /* zero out from the end of the write to the end of the block */
 325                 pad = pos & (fs_block_size - 1);
 326                 if (pad)
 327                         iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
 328         }
 329 out:
 330         /* Undo iter limitation to current extent */
 331         iov_iter_reexpand(dio->submit.iter, orig_count - copied);
 332         if (copied)
 333                 return copied;
 334         return ret;
 335 }
 336
 337 static loff_t
 338 iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
 339 {
 340         length = iov_iter_zero(length, dio->submit.iter);
 341         dio->size += length;
 342         return length;
 343 }
 344
 345 static loff_t
 346 iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
 347                 struct iomap_dio *dio, struct iomap *iomap)
 348 {
 349         struct iov_iter *iter = dio->submit.iter;
 350         size_t copied;
 351
 352         BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
 353
 354         if (dio->flags & IOMAP_DIO_WRITE) {
 355                 loff_t size = inode->i_size;
 356
 357                 if (pos > size)
 358                         memset(iomap->inline_data + size, 0, pos - size);
 359                 copied = copy_from_iter(iomap->inline_data + pos, length, iter);
 360                 if (copied) {
 361                         if (pos + copied > size)
 362                                 i_size_write(inode, pos + copied);
 363                         mark_inode_dirty(inode);
 364                 }
 365         } else {
 366                 copied = copy_to_iter(iomap->inline_data + pos, length, iter);
 367         }
 368         dio->size += copied;
 369         return copied;
 370 }
 371
 372 static loff_t
 373 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 374                 void *data, struct iomap *iomap, struct iomap *srcmap)
 375 {
 376         struct iomap_dio *dio = data;
 377
 378         switch (iomap->type) {
 379         case IOMAP_HOLE:
 380                 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
 381                         return -EIO;
 382                 return iomap_dio_hole_actor(length, dio);
 383         case IOMAP_UNWRITTEN:
 384                 if (!(dio->flags & IOMAP_DIO_WRITE))
 385                         return iomap_dio_hole_actor(length, dio);
 386                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 387         case IOMAP_MAPPED:
 388                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 389         case IOMAP_INLINE:
 390                 return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
 391         default:
 392                 WARN_ON_ONCE(1);
 393                 return -EIO;
 394         }
 395 }
 396
 397 /*
 398  * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
 399  * is being issued as AIO or not.  This allows us to optimise pure data writes
 400  * to use REQ_FUA rather than requiring generic_write_sync() to issue a
 401  * REQ_FLUSH post write. This is slightly tricky because a single request here
 402  * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
 403  * may be pure data writes. In that case, we still need to do a full data sync
 404  * completion.
 405  *
 406  * Returns -ENOTBLK In case of a page invalidation invalidation failure for
 407  * writes.  The callers needs to fall back to buffered I/O in this case.
 408  */
 409 ssize_t
 410 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 411                 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
 412                 bool wait_for_completion)
 413 {
 414         struct address_space *mapping = iocb->ki_filp->f_mapping;
 415         struct inode *inode = file_inode(iocb->ki_filp);
 416         size_t count = iov_iter_count(iter);
 417         loff_t pos = iocb->ki_pos;
 418         loff_t end = iocb->ki_pos + count - 1, ret = 0;
 419         unsigned int flags = IOMAP_DIRECT;
 420         struct blk_plug plug;
 421         struct iomap_dio *dio;
 422
 423         if (!count)
 424                 return 0;
 425
 426         if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))
 427                 return -EIO;
 428
 429         dio = kmalloc(sizeof(*dio), GFP_KERNEL);
 430         if (!dio)
 431                 return -ENOMEM;
 432
 433         dio->iocb = iocb;
 434         atomic_set(&dio->ref, 1);
 435         dio->size = 0;
 436         dio->i_size = i_size_read(inode);
 437         dio->dops = dops;
 438         dio->error = 0;
 439         dio->flags = 0;
 440
 441         dio->submit.iter = iter;
 442         dio->submit.waiter = current;
 443         dio->submit.cookie = BLK_QC_T_NONE;
 444         dio->submit.last_queue = NULL;
 445
 446         if (iov_iter_rw(iter) == READ) {
 447                 if (pos >= dio->i_size)
 448                         goto out_free_dio;
 449
 450                 if (iter_is_iovec(iter))
 451                         dio->flags |= IOMAP_DIO_DIRTY;
 452         } else {
 453                 flags |= IOMAP_WRITE;
 454                 dio->flags |= IOMAP_DIO_WRITE;
 455
 456                 /* for data sync or sync, we need sync completion processing */
 457                 if (iocb->ki_flags & IOCB_DSYNC)
 458                         dio->flags |= IOMAP_DIO_NEED_SYNC;
 459
 460                 /*
 461                  * For datasync only writes, we optimistically try using FUA for
 462                  * this IO.  Any non-FUA write that occurs will clear this flag,
 463                  * hence we know before completion whether a cache flush is
 464                  * necessary.
 465                  */
 466                 if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
 467                         dio->flags |= IOMAP_DIO_WRITE_FUA;
 468         }
 469
 470         if (iocb->ki_flags & IOCB_NOWAIT) {
 471                 if (filemap_range_has_page(mapping, pos, end)) {
 472                         ret = -EAGAIN;
 473                         goto out_free_dio;
 474                 }
 475                 flags |= IOMAP_NOWAIT;
 476         }
 477
 478         ret = filemap_write_and_wait_range(mapping, pos, end);
 479         if (ret)
 480                 goto out_free_dio;
 481
 482         if (iov_iter_rw(iter) == WRITE) {
 483                 /*
 484                  * Try to invalidate cache pages for the range we are writing.
 485                  * If this invalidation fails, let the caller fall back to
 486                  * buffered I/O.
 487                  */
 488                 if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
 489                                 end >> PAGE_SHIFT)) {
 490                         trace_iomap_dio_invalidate_fail(inode, pos, count);
 491                         ret = -ENOTBLK;
 492                         goto out_free_dio;
 493                 }
 494
 495                 if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
 496                         ret = sb_init_dio_done_wq(inode->i_sb);
 497                         if (ret < 0)
 498                                 goto out_free_dio;
 499                 }
 500         }
 501
 502         inode_dio_begin(inode);
 503
 504         blk_start_plug(&plug);
 505         do {
 506                 ret = iomap_apply(inode, pos, count, flags, ops, dio,
 507                                 iomap_dio_actor);
 508                 if (ret <= 0) {
 509                         /* magic error code to fall back to buffered I/O */
 510                         if (ret == -ENOTBLK) {
 511                                 wait_for_completion = true;
 512                                 ret = 0;
 513                         }
 514                         break;
 515                 }
 516                 pos += ret;
 517
 518                 if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
 519                         /*
 520                          * We only report that we've read data up to i_size.
 521                          * Revert iter to a state corresponding to that as
 522                          * some callers (such as splice code) rely on it.
 523                          */
 524                         iov_iter_revert(iter, pos - dio->i_size);
 525                         break;
 526                 }
 527         } while ((count = iov_iter_count(iter)) > 0);
 528         blk_finish_plug(&plug);
 529
 530         if (ret < 0)
 531                 iomap_dio_set_error(dio, ret);
 532
 533         /*
 534          * If all the writes we issued were FUA, we don't need to flush the
 535          * cache on IO completion. Clear the sync flag for this case.
 536          */
 537         if (dio->flags & IOMAP_DIO_WRITE_FUA)
 538                 dio->flags &= ~IOMAP_DIO_NEED_SYNC;
 539
 540         WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
 541         WRITE_ONCE(iocb->private, dio->submit.last_queue);
 542
 543         /*
 544          * We are about to drop our additional submission reference, which
 545          * might be the last reference to the dio.  There are three different
 546          * ways we can progress here:
 547          *
 548          *  (a) If this is the last reference we will always complete and free
 549          *      the dio ourselves.
 550          *  (b) If this is not the last reference, and we serve an asynchronous
 551          *      iocb, we must never touch the dio after the decrement, the
 552          *      I/O completion handler will complete and free it.
 553          *  (c) If this is not the last reference, but we serve a synchronous
 554          *      iocb, the I/O completion handler will wake us up on the drop
 555          *      of the final reference, and we will complete and free it here
 556          *      after we got woken by the I/O completion handler.
 557          */
 558         dio->wait_for_completion = wait_for_completion;
 559         if (!atomic_dec_and_test(&dio->ref)) {
 560                 if (!wait_for_completion)
 561                         return -EIOCBQUEUED;
 562
 563                 for (;;) {
 564                         set_current_state(TASK_UNINTERRUPTIBLE);
 565                         if (!READ_ONCE(dio->submit.waiter))
 566                                 break;
 567
 568                         if (!(iocb->ki_flags & IOCB_HIPRI) ||
 569                             !dio->submit.last_queue ||
 570                             !blk_poll(dio->submit.last_queue,
 571                                          dio->submit.cookie, true))
 572                                 blk_io_schedule();
 573                 }
 574                 __set_current_state(TASK_RUNNING);
 575         }
 576
 577         return iomap_dio_complete(dio);
 578
 579 out_free_dio:
 580         kfree(dio);
 581         return ret;
 582 }
 583 EXPORT_SYMBOL_GPL(iomap_dio_rw);