// SPDX-License-Identifier: GPL-2.0 #include #include #include "ctree.h" #include "delalloc-space.h" #include "direct-io.h" #include "extent-tree.h" #include "file.h" #include "fs.h" #include "transaction.h" #include "volumes.h" struct btrfs_dio_data { ssize_t submitted; struct extent_changeset *data_reserved; struct btrfs_ordered_extent *ordered; bool data_space_reserved; bool nocow_done; }; struct btrfs_dio_private { /* Range of I/O */ u64 file_offset; u32 bytes; /* This must be last */ struct btrfs_bio bbio; }; static struct bio_set btrfs_dio_bioset; static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend, struct extent_state **cached_state, unsigned int iomap_flags) { const bool writing = (iomap_flags & IOMAP_WRITE); const bool nowait = (iomap_flags & IOMAP_NOWAIT); struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; struct btrfs_ordered_extent *ordered; int ret = 0; while (1) { if (nowait) { if (!try_lock_extent(io_tree, lockstart, lockend, cached_state)) return -EAGAIN; } else { lock_extent(io_tree, lockstart, lockend, cached_state); } /* * We're concerned with the entire range that we're going to be * doing DIO to, so we need to make sure there's no ordered * extents in this range. */ ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), lockstart, lockend - lockstart + 1); /* * We need to make sure there are no buffered pages in this * range either, we could have raced between the invalidate in * generic_file_direct_write and locking the extent. The * invalidate needs to happen so that reads after a write do not * get stale data. */ if (!ordered && (!writing || !filemap_range_has_page(inode->i_mapping, lockstart, lockend))) break; unlock_extent(io_tree, lockstart, lockend, cached_state); if (ordered) { if (nowait) { btrfs_put_ordered_extent(ordered); ret = -EAGAIN; break; } /* * If we are doing a DIO read and the ordered extent we * found is for a buffered write, we can not wait for it * to complete and retry, because if we do so we can * deadlock with concurrent buffered writes on page * locks. This happens only if our DIO read covers more * than one extent map, if at this point has already * created an ordered extent for a previous extent map * and locked its range in the inode's io tree, and a * concurrent write against that previous extent map's * range and this range started (we unlock the ranges * in the io tree only when the bios complete and * buffered writes always lock pages before attempting * to lock range in the io tree). */ if (writing || test_bit(BTRFS_ORDERED_DIRECT, &ordered->flags)) btrfs_start_ordered_extent(ordered); else ret = nowait ? -EAGAIN : -ENOTBLK; btrfs_put_ordered_extent(ordered); } else { /* * We could trigger writeback for this range (and wait * for it to complete) and then invalidate the pages for * this range (through invalidate_inode_pages2_range()), * but that can lead us to a deadlock with a concurrent * call to readahead (a buffered read or a defrag call * triggered a readahead) on a page lock due to an * ordered dio extent we created before but did not have * yet a corresponding bio submitted (whence it can not * complete), which makes readahead wait for that * ordered extent to complete while holding a lock on * that page. */ ret = nowait ? -EAGAIN : -ENOTBLK; } if (ret) break; cond_resched(); } return ret; } static struct extent_map *btrfs_create_dio_extent(struct btrfs_inode *inode, struct btrfs_dio_data *dio_data, const u64 start, const struct btrfs_file_extent *file_extent, const int type) { struct extent_map *em = NULL; struct btrfs_ordered_extent *ordered; if (type != BTRFS_ORDERED_NOCOW) { em = btrfs_create_io_em(inode, start, file_extent, type); if (IS_ERR(em)) goto out; } ordered = btrfs_alloc_ordered_extent(inode, start, file_extent, (1 << type) | (1 << BTRFS_ORDERED_DIRECT)); if (IS_ERR(ordered)) { if (em) { free_extent_map(em); btrfs_drop_extent_map_range(inode, start, start + file_extent->num_bytes - 1, false); } em = ERR_CAST(ordered); } else { ASSERT(!dio_data->ordered); dio_data->ordered = ordered; } out: return em; } static struct extent_map *btrfs_new_extent_direct(struct btrfs_inode *inode, struct btrfs_dio_data *dio_data, u64 start, u64 len) { struct btrfs_root *root = inode->root; struct btrfs_fs_info *fs_info = root->fs_info; struct btrfs_file_extent file_extent; struct extent_map *em; struct btrfs_key ins; u64 alloc_hint; int ret; alloc_hint = btrfs_get_extent_allocation_hint(inode, start, len); again: ret = btrfs_reserve_extent(root, len, len, fs_info->sectorsize, 0, alloc_hint, &ins, 1, 1); if (ret == -EAGAIN) { ASSERT(btrfs_is_zoned(fs_info)); wait_on_bit_io(&inode->root->fs_info->flags, BTRFS_FS_NEED_ZONE_FINISH, TASK_UNINTERRUPTIBLE); goto again; } if (ret) return ERR_PTR(ret); file_extent.disk_bytenr = ins.objectid; file_extent.disk_num_bytes = ins.offset; file_extent.num_bytes = ins.offset; file_extent.ram_bytes = ins.offset; file_extent.offset = 0; file_extent.compression = BTRFS_COMPRESS_NONE; em = btrfs_create_dio_extent(inode, dio_data, start, &file_extent, BTRFS_ORDERED_REGULAR); btrfs_dec_block_group_reservations(fs_info, ins.objectid); if (IS_ERR(em)) btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1); return em; } static int btrfs_get_blocks_direct_write(struct extent_map **map, struct inode *inode, struct btrfs_dio_data *dio_data, u64 start, u64 *lenp, unsigned int iomap_flags) { const bool nowait = (iomap_flags & IOMAP_NOWAIT); struct btrfs_fs_info *fs_info = inode_to_fs_info(inode); struct btrfs_file_extent file_extent; struct extent_map *em = *map; int type; u64 block_start; struct btrfs_block_group *bg; bool can_nocow = false; bool space_reserved = false; u64 len = *lenp; u64 prev_len; int ret = 0; /* * We don't allocate a new extent in the following cases * * 1) The inode is marked as NODATACOW. In this case we'll just use the * existing extent. * 2) The extent is marked as PREALLOC. We're good to go here and can * just use the extent. * */ if ((em->flags & EXTENT_FLAG_PREALLOC) || ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) && em->disk_bytenr != EXTENT_MAP_HOLE)) { if (em->flags & EXTENT_FLAG_PREALLOC) type = BTRFS_ORDERED_PREALLOC; else type = BTRFS_ORDERED_NOCOW; len = min(len, em->len - (start - em->start)); block_start = extent_map_block_start(em) + (start - em->start); if (can_nocow_extent(inode, start, &len, &file_extent, false, false) == 1) { bg = btrfs_inc_nocow_writers(fs_info, block_start); if (bg) can_nocow = true; } } prev_len = len; if (can_nocow) { struct extent_map *em2; /* We can NOCOW, so only need to reserve metadata space. */ ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), len, len, nowait); if (ret < 0) { /* Our caller expects us to free the input extent map. */ free_extent_map(em); *map = NULL; btrfs_dec_nocow_writers(bg); if (nowait && (ret == -ENOSPC || ret == -EDQUOT)) ret = -EAGAIN; goto out; } space_reserved = true; em2 = btrfs_create_dio_extent(BTRFS_I(inode), dio_data, start, &file_extent, type); btrfs_dec_nocow_writers(bg); if (type == BTRFS_ORDERED_PREALLOC) { free_extent_map(em); *map = em2; em = em2; } if (IS_ERR(em2)) { ret = PTR_ERR(em2); goto out; } dio_data->nocow_done = true; } else { /* Our caller expects us to free the input extent map. */ free_extent_map(em); *map = NULL; if (nowait) { ret = -EAGAIN; goto out; } /* * If we could not allocate data space before locking the file * range and we can't do a NOCOW write, then we have to fail. */ if (!dio_data->data_space_reserved) { ret = -ENOSPC; goto out; } /* * We have to COW and we have already reserved data space before, * so now we reserve only metadata. */ ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), len, len, false); if (ret < 0) goto out; space_reserved = true; em = btrfs_new_extent_direct(BTRFS_I(inode), dio_data, start, len); if (IS_ERR(em)) { ret = PTR_ERR(em); goto out; } *map = em; len = min(len, em->len - (start - em->start)); if (len < prev_len) btrfs_delalloc_release_metadata(BTRFS_I(inode), prev_len - len, true); } /* * We have created our ordered extent, so we can now release our reservation * for an outstanding extent. */ btrfs_delalloc_release_extents(BTRFS_I(inode), prev_len); /* * Need to update the i_size under the extent lock so buffered * readers will get the updated i_size when we unlock. */ if (start + len > i_size_read(inode)) i_size_write(inode, start + len); out: if (ret && space_reserved) { btrfs_delalloc_release_extents(BTRFS_I(inode), len); btrfs_delalloc_release_metadata(BTRFS_I(inode), len, true); } *lenp = len; return ret; } static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start, loff_t length, unsigned int flags, struct iomap *iomap, struct iomap *srcmap) { struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap); struct btrfs_fs_info *fs_info = inode_to_fs_info(inode); struct extent_map *em; struct extent_state *cached_state = NULL; struct btrfs_dio_data *dio_data = iter->private; u64 lockstart, lockend; const bool write = !!(flags & IOMAP_WRITE); int ret = 0; u64 len = length; const u64 data_alloc_len = length; bool unlock_extents = false; /* * We could potentially fault if we have a buffer > PAGE_SIZE, and if * we're NOWAIT we may submit a bio for a partial range and return * EIOCBQUEUED, which would result in an errant short read. * * The best way to handle this would be to allow for partial completions * of iocb's, so we could submit the partial bio, return and fault in * the rest of the pages, and then submit the io for the rest of the * range. However we don't have that currently, so simply return * -EAGAIN at this point so that the normal path is used. */ if (!write && (flags & IOMAP_NOWAIT) && length > PAGE_SIZE) return -EAGAIN; /* * Cap the size of reads to that usually seen in buffered I/O as we need * to allocate a contiguous array for the checksums. */ if (!write) len = min_t(u64, len, fs_info->sectorsize * BTRFS_MAX_BIO_SECTORS); lockstart = start; lockend = start + len - 1; /* * iomap_dio_rw() only does filemap_write_and_wait_range(), which isn't * enough if we've written compressed pages to this area, so we need to * flush the dirty pages again to make absolutely sure that any * outstanding dirty pages are on disk - the first flush only starts * compression on the data, while keeping the pages locked, so by the * time the second flush returns we know bios for the compressed pages * were submitted and finished, and the pages no longer under writeback. * * If we have a NOWAIT request and we have any pages in the range that * are locked, likely due to compression still in progress, we don't want * to block on page locks. We also don't want to block on pages marked as * dirty or under writeback (same as for the non-compression case). * iomap_dio_rw() did the same check, but after that and before we got * here, mmap'ed writes may have happened or buffered reads started * (readpage() and readahead(), which lock pages), as we haven't locked * the file range yet. */ if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, &BTRFS_I(inode)->runtime_flags)) { if (flags & IOMAP_NOWAIT) { if (filemap_range_needs_writeback(inode->i_mapping, lockstart, lockend)) return -EAGAIN; } else { ret = filemap_fdatawrite_range(inode->i_mapping, start, start + length - 1); if (ret) return ret; } } memset(dio_data, 0, sizeof(*dio_data)); /* * We always try to allocate data space and must do it before locking * the file range, to avoid deadlocks with concurrent writes to the same * range if the range has several extents and the writes don't expand the * current i_size (the inode lock is taken in shared mode). If we fail to * allocate data space here we continue and later, after locking the * file range, we fail with ENOSPC only if we figure out we can not do a * NOCOW write. */ if (write && !(flags & IOMAP_NOWAIT)) { ret = btrfs_check_data_free_space(BTRFS_I(inode), &dio_data->data_reserved, start, data_alloc_len, false); if (!ret) dio_data->data_space_reserved = true; else if (ret && !(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC))) goto err; } /* * If this errors out it's because we couldn't invalidate pagecache for * this range and we need to fallback to buffered IO, or we are doing a * NOWAIT read/write and we need to block. */ ret = lock_extent_direct(inode, lockstart, lockend, &cached_state, flags); if (ret < 0) goto err; em = btrfs_get_extent(BTRFS_I(inode), NULL, start, len); if (IS_ERR(em)) { ret = PTR_ERR(em); goto unlock_err; } /* * Ok for INLINE and COMPRESSED extents we need to fallback on buffered * io. INLINE is special, and we could probably kludge it in here, but * it's still buffered so for safety lets just fall back to the generic * buffered path. * * For COMPRESSED we _have_ to read the entire extent in so we can * decompress it, so there will be buffering required no matter what we * do, so go ahead and fallback to buffered. * * We return -ENOTBLK because that's what makes DIO go ahead and go back * to buffered IO. Don't blame me, this is the price we pay for using * the generic code. */ if (extent_map_is_compressed(em) || em->disk_bytenr == EXTENT_MAP_INLINE) { free_extent_map(em); /* * If we are in a NOWAIT context, return -EAGAIN in order to * fallback to buffered IO. This is not only because we can * block with buffered IO (no support for NOWAIT semantics at * the moment) but also to avoid returning short reads to user * space - this happens if we were able to read some data from * previous non-compressed extents and then when we fallback to * buffered IO, at btrfs_file_read_iter() by calling * filemap_read(), we fail to fault in pages for the read buffer, * in which case filemap_read() returns a short read (the number * of bytes previously read is > 0, so it does not return -EFAULT). */ ret = (flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOTBLK; goto unlock_err; } len = min(len, em->len - (start - em->start)); /* * If we have a NOWAIT request and the range contains multiple extents * (or a mix of extents and holes), then we return -EAGAIN to make the * caller fallback to a context where it can do a blocking (without * NOWAIT) request. This way we avoid doing partial IO and returning * success to the caller, which is not optimal for writes and for reads * it can result in unexpected behaviour for an application. * * When doing a read, because we use IOMAP_DIO_PARTIAL when calling * iomap_dio_rw(), we can end up returning less data then what the caller * asked for, resulting in an unexpected, and incorrect, short read. * That is, the caller asked to read N bytes and we return less than that, * which is wrong unless we are crossing EOF. This happens if we get a * page fault error when trying to fault in pages for the buffer that is * associated to the struct iov_iter passed to iomap_dio_rw(), and we * have previously submitted bios for other extents in the range, in * which case iomap_dio_rw() may return us EIOCBQUEUED if not all of * those bios have completed by the time we get the page fault error, * which we return back to our caller - we should only return EIOCBQUEUED * after we have submitted bios for all the extents in the range. */ if ((flags & IOMAP_NOWAIT) && len < length) { free_extent_map(em); ret = -EAGAIN; goto unlock_err; } if (write) { ret = btrfs_get_blocks_direct_write(&em, inode, dio_data, start, &len, flags); if (ret < 0) goto unlock_err; unlock_extents = true; /* Recalc len in case the new em is smaller than requested */ len = min(len, em->len - (start - em->start)); if (dio_data->data_space_reserved) { u64 release_offset; u64 release_len = 0; if (dio_data->nocow_done) { release_offset = start; release_len = data_alloc_len; } else if (len < data_alloc_len) { release_offset = start + len; release_len = data_alloc_len - len; } if (release_len > 0) btrfs_free_reserved_data_space(BTRFS_I(inode), dio_data->data_reserved, release_offset, release_len); } } else { /* * We need to unlock only the end area that we aren't using. * The rest is going to be unlocked by the endio routine. */ lockstart = start + len; if (lockstart < lockend) unlock_extents = true; } if (unlock_extents) unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend, &cached_state); else free_extent_state(cached_state); /* * Translate extent map information to iomap. * We trim the extents (and move the addr) even though iomap code does * that, since we have locked only the parts we are performing I/O in. */ if ((em->disk_bytenr == EXTENT_MAP_HOLE) || ((em->flags & EXTENT_FLAG_PREALLOC) && !write)) { iomap->addr = IOMAP_NULL_ADDR; iomap->type = IOMAP_HOLE; } else { iomap->addr = extent_map_block_start(em) + (start - em->start); iomap->type = IOMAP_MAPPED; } iomap->offset = start; iomap->bdev = fs_info->fs_devices->latest_dev->bdev; iomap->length = len; free_extent_map(em); return 0; unlock_err: unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend, &cached_state); err: if (dio_data->data_space_reserved) { btrfs_free_reserved_data_space(BTRFS_I(inode), dio_data->data_reserved, start, data_alloc_len); extent_changeset_free(dio_data->data_reserved); } return ret; } static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos, loff_t length, ssize_t written, unsigned int flags, struct iomap *iomap) { struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap); struct btrfs_dio_data *dio_data = iter->private; size_t submitted = dio_data->submitted; const bool write = !!(flags & IOMAP_WRITE); int ret = 0; if (!write && (iomap->type == IOMAP_HOLE)) { /* If reading from a hole, unlock and return */ unlock_extent(&BTRFS_I(inode)->io_tree, pos, pos + length - 1, NULL); return 0; } if (submitted < length) { pos += submitted; length -= submitted; if (write) btrfs_finish_ordered_extent(dio_data->ordered, NULL, pos, length, false); else unlock_extent(&BTRFS_I(inode)->io_tree, pos, pos + length - 1, NULL); ret = -ENOTBLK; } if (write) { btrfs_put_ordered_extent(dio_data->ordered); dio_data->ordered = NULL; } if (write) extent_changeset_free(dio_data->data_reserved); return ret; } static void btrfs_dio_end_io(struct btrfs_bio *bbio) { struct btrfs_dio_private *dip = container_of(bbio, struct btrfs_dio_private, bbio); struct btrfs_inode *inode = bbio->inode; struct bio *bio = &bbio->bio; if (bio->bi_status) { btrfs_warn(inode->root->fs_info, "direct IO failed ino %llu op 0x%0x offset %#llx len %u err no %d", btrfs_ino(inode), bio->bi_opf, dip->file_offset, dip->bytes, bio->bi_status); } if (btrfs_op(bio) == BTRFS_MAP_WRITE) { btrfs_finish_ordered_extent(bbio->ordered, NULL, dip->file_offset, dip->bytes, !bio->bi_status); } else { unlock_extent(&inode->io_tree, dip->file_offset, dip->file_offset + dip->bytes - 1, NULL); } bbio->bio.bi_private = bbio->private; iomap_dio_bio_end_io(bio); } static int btrfs_extract_ordered_extent(struct btrfs_bio *bbio, struct btrfs_ordered_extent *ordered) { u64 start = (u64)bbio->bio.bi_iter.bi_sector << SECTOR_SHIFT; u64 len = bbio->bio.bi_iter.bi_size; struct btrfs_ordered_extent *new; int ret; /* Must always be called for the beginning of an ordered extent. */ if (WARN_ON_ONCE(start != ordered->disk_bytenr)) return -EINVAL; /* No need to split if the ordered extent covers the entire bio. */ if (ordered->disk_num_bytes == len) { refcount_inc(&ordered->refs); bbio->ordered = ordered; return 0; } /* * Don't split the extent_map for NOCOW extents, as we're writing into * a pre-existing one. */ if (!test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags)) { ret = split_extent_map(bbio->inode, bbio->file_offset, ordered->num_bytes, len, ordered->disk_bytenr); if (ret) return ret; } new = btrfs_split_ordered_extent(ordered, len); if (IS_ERR(new)) return PTR_ERR(new); bbio->ordered = new; return 0; } static void btrfs_dio_submit_io(const struct iomap_iter *iter, struct bio *bio, loff_t file_offset) { struct btrfs_bio *bbio = btrfs_bio(bio); struct btrfs_dio_private *dip = container_of(bbio, struct btrfs_dio_private, bbio); struct btrfs_dio_data *dio_data = iter->private; btrfs_bio_init(bbio, BTRFS_I(iter->inode)->root->fs_info, btrfs_dio_end_io, bio->bi_private); bbio->inode = BTRFS_I(iter->inode); bbio->file_offset = file_offset; dip->file_offset = file_offset; dip->bytes = bio->bi_iter.bi_size; dio_data->submitted += bio->bi_iter.bi_size; /* * Check if we are doing a partial write. If we are, we need to split * the ordered extent to match the submitted bio. Hang on to the * remaining unfinishable ordered_extent in dio_data so that it can be * cancelled in iomap_end to avoid a deadlock wherein faulting the * remaining pages is blocked on the outstanding ordered extent. */ if (iter->flags & IOMAP_WRITE) { int ret; ret = btrfs_extract_ordered_extent(bbio, dio_data->ordered); if (ret) { btrfs_finish_ordered_extent(dio_data->ordered, NULL, file_offset, dip->bytes, !ret); bio->bi_status = errno_to_blk_status(ret); iomap_dio_bio_end_io(bio); return; } } btrfs_submit_bio(bbio, 0); } static const struct iomap_ops btrfs_dio_iomap_ops = { .iomap_begin = btrfs_dio_iomap_begin, .iomap_end = btrfs_dio_iomap_end, }; static const struct iomap_dio_ops btrfs_dio_ops = { .submit_io = btrfs_dio_submit_io, .bio_set = &btrfs_dio_bioset, }; static ssize_t btrfs_dio_read(struct kiocb *iocb, struct iov_iter *iter, size_t done_before) { struct btrfs_dio_data data = { 0 }; return iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops, IOMAP_DIO_PARTIAL, &data, done_before); } static struct iomap_dio *btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter, size_t done_before) { struct btrfs_dio_data data = { 0 }; return __iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops, IOMAP_DIO_PARTIAL, &data, done_before); } static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info, const struct iov_iter *iter, loff_t offset) { const u32 blocksize_mask = fs_info->sectorsize - 1; if (offset & blocksize_mask) return -EINVAL; if (iov_iter_alignment(iter) & blocksize_mask) return -EINVAL; return 0; } ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from) { struct file *file = iocb->ki_filp; struct inode *inode = file_inode(file); struct btrfs_fs_info *fs_info = inode_to_fs_info(inode); loff_t pos; ssize_t written = 0; ssize_t written_buffered; size_t prev_left = 0; loff_t endbyte; ssize_t ret; unsigned int ilock_flags = 0; struct iomap_dio *dio; if (iocb->ki_flags & IOCB_NOWAIT) ilock_flags |= BTRFS_ILOCK_TRY; /* * If the write DIO is within EOF, use a shared lock and also only if * security bits will likely not be dropped by file_remove_privs() called * from btrfs_write_check(). Either will need to be rechecked after the * lock was acquired. */ if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode) && IS_NOSEC(inode)) ilock_flags |= BTRFS_ILOCK_SHARED; relock: ret = btrfs_inode_lock(BTRFS_I(inode), ilock_flags); if (ret < 0) return ret; /* Shared lock cannot be used with security bits set. */ if ((ilock_flags & BTRFS_ILOCK_SHARED) && !IS_NOSEC(inode)) { btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); ilock_flags &= ~BTRFS_ILOCK_SHARED; goto relock; } ret = generic_write_checks(iocb, from); if (ret <= 0) { btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); return ret; } ret = btrfs_write_check(iocb, from, ret); if (ret < 0) { btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); goto out; } pos = iocb->ki_pos; /* * Re-check since file size may have changed just before taking the * lock or pos may have changed because of O_APPEND in generic_write_check() */ if ((ilock_flags & BTRFS_ILOCK_SHARED) && pos + iov_iter_count(from) > i_size_read(inode)) { btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); ilock_flags &= ~BTRFS_ILOCK_SHARED; goto relock; } if (check_direct_IO(fs_info, from, pos)) { btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); goto buffered; } /* * The iov_iter can be mapped to the same file range we are writing to. * If that's the case, then we will deadlock in the iomap code, because * it first calls our callback btrfs_dio_iomap_begin(), which will create * an ordered extent, and after that it will fault in the pages that the * iov_iter refers to. During the fault in we end up in the readahead * pages code (starting at btrfs_readahead()), which will lock the range, * find that ordered extent and then wait for it to complete (at * btrfs_lock_and_flush_ordered_range()), resulting in a deadlock since * obviously the ordered extent can never complete as we didn't submit * yet the respective bio(s). This always happens when the buffer is * memory mapped to the same file range, since the iomap DIO code always * invalidates pages in the target file range (after starting and waiting * for any writeback). * * So here we disable page faults in the iov_iter and then retry if we * got -EFAULT, faulting in the pages before the retry. */ again: from->nofault = true; dio = btrfs_dio_write(iocb, from, written); from->nofault = false; if (IS_ERR_OR_NULL(dio)) { ret = PTR_ERR_OR_ZERO(dio); } else { /* * If we have a synchronous write, we must make sure the fsync * triggered by the iomap_dio_complete() call below doesn't * deadlock on the inode lock - we are already holding it and we * can't call it after unlocking because we may need to complete * partial writes due to the input buffer (or parts of it) not * being already faulted in. */ ASSERT(current->journal_info == NULL); current->journal_info = BTRFS_TRANS_DIO_WRITE_STUB; ret = iomap_dio_complete(dio); current->journal_info = NULL; } /* No increment (+=) because iomap returns a cumulative value. */ if (ret > 0) written = ret; if (iov_iter_count(from) > 0 && (ret == -EFAULT || ret > 0)) { const size_t left = iov_iter_count(from); /* * We have more data left to write. Try to fault in as many as * possible of the remainder pages and retry. We do this without * releasing and locking again the inode, to prevent races with * truncate. * * Also, in case the iov refers to pages in the file range of the * file we want to write to (due to a mmap), we could enter an * infinite loop if we retry after faulting the pages in, since * iomap will invalidate any pages in the range early on, before * it tries to fault in the pages of the iov. So we keep track of * how much was left of iov in the previous EFAULT and fallback * to buffered IO in case we haven't made any progress. */ if (left == prev_left) { ret = -ENOTBLK; } else { fault_in_iov_iter_readable(from, left); prev_left = left; goto again; } } btrfs_inode_unlock(BTRFS_I(inode), ilock_flags); /* * If 'ret' is -ENOTBLK or we have not written all data, then it means * we must fallback to buffered IO. */ if ((ret < 0 && ret != -ENOTBLK) || !iov_iter_count(from)) goto out; buffered: /* * If we are in a NOWAIT context, then return -EAGAIN to signal the caller * it must retry the operation in a context where blocking is acceptable, * because even if we end up not blocking during the buffered IO attempt * below, we will block when flushing and waiting for the IO. */ if (iocb->ki_flags & IOCB_NOWAIT) { ret = -EAGAIN; goto out; } pos = iocb->ki_pos; written_buffered = btrfs_buffered_write(iocb, from); if (written_buffered < 0) { ret = written_buffered; goto out; } /* * Ensure all data is persisted. We want the next direct IO read to be * able to read what was just written. */ endbyte = pos + written_buffered - 1; ret = btrfs_fdatawrite_range(BTRFS_I(inode), pos, endbyte); if (ret) goto out; ret = filemap_fdatawait_range(inode->i_mapping, pos, endbyte); if (ret) goto out; written += written_buffered; iocb->ki_pos = pos + written_buffered; invalidate_mapping_pages(file->f_mapping, pos >> PAGE_SHIFT, endbyte >> PAGE_SHIFT); out: return ret < 0 ? ret : written; } static int check_direct_read(struct btrfs_fs_info *fs_info, const struct iov_iter *iter, loff_t offset) { int ret; int i, seg; ret = check_direct_IO(fs_info, iter, offset); if (ret < 0) return ret; if (!iter_is_iovec(iter)) return 0; for (seg = 0; seg < iter->nr_segs; seg++) { for (i = seg + 1; i < iter->nr_segs; i++) { const struct iovec *iov1 = iter_iov(iter) + seg; const struct iovec *iov2 = iter_iov(iter) + i; if (iov1->iov_base == iov2->iov_base) return -EINVAL; } } return 0; } ssize_t btrfs_direct_read(struct kiocb *iocb, struct iov_iter *to) { struct inode *inode = file_inode(iocb->ki_filp); size_t prev_left = 0; ssize_t read = 0; ssize_t ret; if (fsverity_active(inode)) return 0; if (check_direct_read(inode_to_fs_info(inode), to, iocb->ki_pos)) return 0; btrfs_inode_lock(BTRFS_I(inode), BTRFS_ILOCK_SHARED); again: /* * This is similar to what we do for direct IO writes, see the comment * at btrfs_direct_write(), but we also disable page faults in addition * to disabling them only at the iov_iter level. This is because when * reading from a hole or prealloc extent, iomap calls iov_iter_zero(), * which can still trigger page fault ins despite having set ->nofault * to true of our 'to' iov_iter. * * The difference to direct IO writes is that we deadlock when trying * to lock the extent range in the inode's tree during he page reads * triggered by the fault in (while for writes it is due to waiting for * our own ordered extent). This is because for direct IO reads, * btrfs_dio_iomap_begin() returns with the extent range locked, which * is only unlocked in the endio callback (end_bio_extent_readpage()). */ pagefault_disable(); to->nofault = true; ret = btrfs_dio_read(iocb, to, read); to->nofault = false; pagefault_enable(); /* No increment (+=) because iomap returns a cumulative value. */ if (ret > 0) read = ret; if (iov_iter_count(to) > 0 && (ret == -EFAULT || ret > 0)) { const size_t left = iov_iter_count(to); if (left == prev_left) { /* * We didn't make any progress since the last attempt, * fallback to a buffered read for the remainder of the * range. This is just to avoid any possibility of looping * for too long. */ ret = read; } else { /* * We made some progress since the last retry or this is * the first time we are retrying. Fault in as many pages * as possible and retry. */ fault_in_iov_iter_writeable(to, left); prev_left = left; goto again; } } btrfs_inode_unlock(BTRFS_I(inode), BTRFS_ILOCK_SHARED); return ret < 0 ? ret : read; } int __init btrfs_init_dio(void) { if (bioset_init(&btrfs_dio_bioset, BIO_POOL_SIZE, offsetof(struct btrfs_dio_private, bbio.bio), BIOSET_NEED_BVECS)) return -ENOMEM; return 0; } void __cold btrfs_destroy_dio(void) { bioset_exit(&btrfs_dio_bioset); }