Commit 6450fe1f authored Oct 20, 2021 by Pavel Begunkov Committed by Jens Axboe Oct 21, 2021

block: optimise boundary blkdev_read_iter's checks



Combine pos and len checks and mark unlikely. Also, don't reexpand if
it's not truncated.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/fff34e613aeaae1ad12977dc4592cb1a1f5d3190.1634755800.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 057178cf

block/fops.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -503,16 +503,19 @@ static ssize_t blkdev_read_iter(struct kiocb iocb, struct iov_iter to)
		size_t shorted = 0;
		ssize_t ret;

		if (unlikely(pos + iov_iter_count(to) > size)) {
		if (pos >= size)
		return 0;

		size -= pos;
		if (iov_iter_count(to) > size) {
		shorted = iov_iter_count(to) - size;
		iov_iter_truncate(to, size);
		}
		}

		ret = generic_file_read_iter(iocb, to);

		if (unlikely(shorted))
		iov_iter_reexpand(to, iov_iter_count(to) + shorted);
		return ret;
		}