Commit 542ff7bf authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 78250c02

fs/block_dev.c

+162 −4
Original line number Diff line number Diff line
@@ -270,11 +270,161 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter, 
	return ret;

}



struct blkdev_dio {

	union {

		struct kiocb		*iocb;

		struct task_struct	*waiter;

	};

	size_t			size;

	atomic_t		ref;

	bool			multi_bio : 1;

	bool			should_dirty : 1;

	bool			is_sync : 1;

	struct bio		bio;

};



static struct bio_set *blkdev_dio_pool __read_mostly;



static void blkdev_bio_end_io(struct bio *bio)

{

	struct blkdev_dio *dio = bio->bi_private;

	bool should_dirty = dio->should_dirty;



	if (dio->multi_bio && !atomic_dec_and_test(&dio->ref)) {

		if (bio->bi_error && !dio->bio.bi_error)

			dio->bio.bi_error = bio->bi_error;

	} else {

		if (!dio->is_sync) {

			struct kiocb *iocb = dio->iocb;

			ssize_t ret = dio->bio.bi_error;



			if (likely(!ret)) {

				ret = dio->size;

				iocb->ki_pos += ret;

			}



			dio->iocb->ki_complete(iocb, ret, 0);

			bio_put(&dio->bio);

		} else {

			struct task_struct *waiter = dio->waiter;



			WRITE_ONCE(dio->waiter, NULL);

			wake_up_process(waiter);

		}

	}



	if (should_dirty) {

		bio_check_pages_dirty(bio);

	} else {

		struct bio_vec *bvec;

		int i;



		bio_for_each_segment_all(bvec, bio, i)

			put_page(bvec->bv_page);

		bio_put(bio);

	}

}



static ssize_t

blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)

__blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = bdev_file_inode(file);

	struct block_device *bdev = I_BDEV(inode);

	unsigned blkbits = blksize_bits(bdev_logical_block_size(bdev));

	struct blkdev_dio *dio;

	struct bio *bio;

	bool is_read = (iov_iter_rw(iter) == READ);

	loff_t pos = iocb->ki_pos;

	blk_qc_t qc = BLK_QC_T_NONE;

	int ret;



	if ((pos | iov_iter_alignment(iter)) & ((1 << blkbits) - 1))

		return -EINVAL;



	bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, blkdev_dio_pool);

	bio_get(bio); /* extra ref for the completion handler */



	dio = container_of(bio, struct blkdev_dio, bio);

	dio->is_sync = is_sync_kiocb(iocb);

	if (dio->is_sync)

		dio->waiter = current;

	else

		dio->iocb = iocb;



	dio->size = 0;

	dio->multi_bio = false;

	dio->should_dirty = is_read && (iter->type == ITER_IOVEC);



	for (;;) {

		bio->bi_bdev = bdev;

		bio->bi_iter.bi_sector = pos >> blkbits;

		bio->bi_private = dio;

		bio->bi_end_io = blkdev_bio_end_io;



		ret = bio_iov_iter_get_pages(bio, iter);

		if (unlikely(ret)) {

			bio->bi_error = ret;

			bio_endio(bio);

			break;

		}



		if (is_read) {

			bio->bi_opf = REQ_OP_READ;

			if (dio->should_dirty)

				bio_set_pages_dirty(bio);

		} else {

			bio->bi_opf = dio_bio_write_op(iocb);

			task_io_account_write(bio->bi_iter.bi_size);

		}



		dio->size += bio->bi_iter.bi_size;

		pos += bio->bi_iter.bi_size;



		nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);

		if (!nr_pages) {

			qc = submit_bio(bio);

			break;

		}



		if (!dio->multi_bio) {

			dio->multi_bio = true;

			atomic_set(&dio->ref, 2);

		} else {

			atomic_inc(&dio->ref);

		}



		submit_bio(bio);

		bio = bio_alloc(GFP_KERNEL, nr_pages);

	}



	if (!dio->is_sync)

		return -EIOCBQUEUED;



	for (;;) {

		set_current_state(TASK_UNINTERRUPTIBLE);

		if (!READ_ONCE(dio->waiter))

			break;



		if (!(iocb->ki_flags & IOCB_HIPRI) ||

		    !blk_mq_poll(bdev_get_queue(bdev), qc))

			io_schedule();

	}

	__set_current_state(TASK_RUNNING);



	ret = dio->bio.bi_error;

	if (likely(!ret)) {

		ret = dio->size;

		iocb->ki_pos += ret;

	}



	bio_put(&dio->bio);

	return ret;

}



static ssize_t

blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)

{

	int nr_pages;



	nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
@@ -282,10 +432,18 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 
		return 0;

	if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)

		return __blkdev_direct_IO_simple(iocb, iter, nr_pages);

	return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter,

				    blkdev_get_block, NULL, NULL,

				    DIO_SKIP_DIO_COUNT);



	return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));

}



static __init int blkdev_init(void)

{

	blkdev_dio_pool = bioset_create(4, offsetof(struct blkdev_dio, bio));

	if (!blkdev_dio_pool)

		return -ENOMEM;

	return 0;

}

module_init(blkdev_init);



int __sync_blockdev(struct block_device *bdev, int wait)

{

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