diff mbox series

[09/16] block: optimise boundary blkdev_read_iter's checks

Message ID d8660b783e2237063a00f671afcf17a30c2e2c76.1634676157.git.asml.silence@gmail.com (mailing list archive)
State New, archived
Headers show
Series block optimisation round | expand

Commit Message

Pavel Begunkov Oct. 19, 2021, 9:24 p.m. UTC 
Combine pos and len checks and mark unlikely. Also, don't reexpand if
it's not truncated.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 block/fops.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

Comments

Christoph Hellwig Oct. 20, 2021, 6:29 a.m. UTC | #1 
On Tue, Oct 19, 2021 at 10:24:18PM +0100, Pavel Begunkov wrote:
> Combine pos and len checks and mark unlikely. Also, don't reexpand if
> it's not truncated.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/block/fops.c b/block/fops.c
index 21d25ee0e4bf..8f733c919ed1 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -503,17 +503,20 @@  static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	size_t shorted = 0;
 	ssize_t ret;
 
-	if (pos >= size)
-		return 0;
-
-	size -= pos;
-	if (iov_iter_count(to) > size) {
-		shorted = iov_iter_count(to) - size;
-		iov_iter_truncate(to, size);
+	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);
-	iov_iter_reexpand(to, iov_iter_count(to) + shorted);
+
+	if (unlikely(shorted))
+		iov_iter_reexpand(to, iov_iter_count(to) + shorted);
 	return ret;
 }