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block: new direct I/O implementation
Similar to the simple fast path, but we now need a dio structure to track multiple-bio completions. It's basically a cut-down version of the new iomap-based direct I/O code for filesystems, but without all the logic to call into the filesystem for extent lookup or allocation, and without the complex I/O completion workqueue handler for AIO - instead we just use the FUA bit on the bios to ensure data is flushed to stable storage. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
Jens Axboe
parent
78250c02d9
commit
542ff7bf18
166
fs/block_dev.c
166
fs/block_dev.c
@ -270,11 +270,161 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
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return ret;
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}
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struct blkdev_dio {
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union {
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struct kiocb *iocb;
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struct task_struct *waiter;
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};
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size_t size;
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atomic_t ref;
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bool multi_bio : 1;
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bool should_dirty : 1;
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bool is_sync : 1;
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struct bio bio;
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};
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static struct bio_set *blkdev_dio_pool __read_mostly;
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static void blkdev_bio_end_io(struct bio *bio)
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{
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struct blkdev_dio *dio = bio->bi_private;
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bool should_dirty = dio->should_dirty;
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if (dio->multi_bio && !atomic_dec_and_test(&dio->ref)) {
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if (bio->bi_error && !dio->bio.bi_error)
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dio->bio.bi_error = bio->bi_error;
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} else {
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if (!dio->is_sync) {
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struct kiocb *iocb = dio->iocb;
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ssize_t ret = dio->bio.bi_error;
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if (likely(!ret)) {
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ret = dio->size;
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iocb->ki_pos += ret;
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}
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dio->iocb->ki_complete(iocb, ret, 0);
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bio_put(&dio->bio);
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} else {
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struct task_struct *waiter = dio->waiter;
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WRITE_ONCE(dio->waiter, NULL);
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wake_up_process(waiter);
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}
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}
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if (should_dirty) {
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bio_check_pages_dirty(bio);
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} else {
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struct bio_vec *bvec;
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int i;
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bio_for_each_segment_all(bvec, bio, i)
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put_page(bvec->bv_page);
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bio_put(bio);
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}
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}
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static ssize_t
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blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
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__blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
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{
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struct file *file = iocb->ki_filp;
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struct inode *inode = bdev_file_inode(file);
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struct block_device *bdev = I_BDEV(inode);
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unsigned blkbits = blksize_bits(bdev_logical_block_size(bdev));
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struct blkdev_dio *dio;
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struct bio *bio;
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bool is_read = (iov_iter_rw(iter) == READ);
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loff_t pos = iocb->ki_pos;
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blk_qc_t qc = BLK_QC_T_NONE;
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int ret;
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if ((pos | iov_iter_alignment(iter)) & ((1 << blkbits) - 1))
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return -EINVAL;
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bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, blkdev_dio_pool);
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bio_get(bio); /* extra ref for the completion handler */
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dio = container_of(bio, struct blkdev_dio, bio);
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dio->is_sync = is_sync_kiocb(iocb);
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if (dio->is_sync)
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dio->waiter = current;
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else
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dio->iocb = iocb;
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dio->size = 0;
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dio->multi_bio = false;
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dio->should_dirty = is_read && (iter->type == ITER_IOVEC);
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for (;;) {
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bio->bi_bdev = bdev;
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bio->bi_iter.bi_sector = pos >> blkbits;
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bio->bi_private = dio;
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bio->bi_end_io = blkdev_bio_end_io;
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ret = bio_iov_iter_get_pages(bio, iter);
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if (unlikely(ret)) {
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bio->bi_error = ret;
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bio_endio(bio);
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break;
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}
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if (is_read) {
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bio->bi_opf = REQ_OP_READ;
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if (dio->should_dirty)
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bio_set_pages_dirty(bio);
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} else {
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bio->bi_opf = dio_bio_write_op(iocb);
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task_io_account_write(bio->bi_iter.bi_size);
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}
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dio->size += bio->bi_iter.bi_size;
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pos += bio->bi_iter.bi_size;
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nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
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if (!nr_pages) {
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qc = submit_bio(bio);
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break;
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}
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if (!dio->multi_bio) {
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dio->multi_bio = true;
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atomic_set(&dio->ref, 2);
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} else {
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atomic_inc(&dio->ref);
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}
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submit_bio(bio);
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bio = bio_alloc(GFP_KERNEL, nr_pages);
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}
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if (!dio->is_sync)
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return -EIOCBQUEUED;
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for (;;) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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if (!READ_ONCE(dio->waiter))
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break;
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if (!(iocb->ki_flags & IOCB_HIPRI) ||
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!blk_mq_poll(bdev_get_queue(bdev), qc))
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io_schedule();
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}
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__set_current_state(TASK_RUNNING);
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ret = dio->bio.bi_error;
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if (likely(!ret)) {
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ret = dio->size;
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iocb->ki_pos += ret;
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}
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bio_put(&dio->bio);
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return ret;
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}
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static ssize_t
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blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
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{
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int nr_pages;
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nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
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@ -282,11 +432,19 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
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return 0;
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if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
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return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
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return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter,
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blkdev_get_block, NULL, NULL,
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DIO_SKIP_DIO_COUNT);
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return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));
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}
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static __init int blkdev_init(void)
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{
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blkdev_dio_pool = bioset_create(4, offsetof(struct blkdev_dio, bio));
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if (!blkdev_dio_pool)
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return -ENOMEM;
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return 0;
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}
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module_init(blkdev_init);
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int __sync_blockdev(struct block_device *bdev, int wait)
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{
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if (!bdev)
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