Commit ceaa7625 authored by Jens Axboe's avatar Jens Axboe
Browse files

block: move direct_IO into our own read_iter handler 



Don't call into generic_file_read_iter() if we know it's O_DIRECT, just
set it up ourselves and call our own handler. This avoids an indirect call
for O_DIRECT.

Fall back to filemap_read() if we fail.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4bdcd1dd

block/fops.c

+32 −5
Original line number Diff line number Diff line
@@ -566,21 +566,48 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) 
{

	struct block_device *bdev = iocb->ki_filp->private_data;

	loff_t size = bdev_nr_bytes(bdev);

	size_t count = iov_iter_count(to);

	loff_t pos = iocb->ki_pos;

	size_t shorted = 0;

	ssize_t ret;

	ssize_t ret = 0;



	if (unlikely(pos + iov_iter_count(to) > size)) {

	if (unlikely(pos + count > size)) {

		if (pos >= size)

			return 0;

		size -= pos;

		if (iov_iter_count(to) > size) {

			shorted = iov_iter_count(to) - size;

		if (count > size) {

			shorted = count - size;

			iov_iter_truncate(to, size);

		}

	}



	ret = generic_file_read_iter(iocb, to);

	if (iocb->ki_flags & IOCB_DIRECT) {

		struct address_space *mapping = iocb->ki_filp->f_mapping;



		if (iocb->ki_flags & IOCB_NOWAIT) {

			if (filemap_range_needs_writeback(mapping, iocb->ki_pos,

						iocb->ki_pos + count - 1))

				return -EAGAIN;

		} else {

			ret = filemap_write_and_wait_range(mapping,

						iocb->ki_pos,

					        iocb->ki_pos + count - 1);

			if (ret < 0)

				return ret;

		}



		file_accessed(iocb->ki_filp);



		ret = blkdev_direct_IO(iocb, to);

		if (ret >= 0) {

			iocb->ki_pos += ret;

			count -= ret;

		}

		if (ret < 0 || !count)

			return ret;

	}



	ret = filemap_read(iocb, to, ret);



	if (unlikely(shorted))

		iov_iter_reexpand(to, iov_iter_count(to) + shorted);