From: Pavel Begunkov <asml.silence@gmail.com>
To: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>,
Pavel Begunkov <asml.silence@gmail.com>,
Christoph Hellwig <hch@lst.de>
Subject: [PATCH 1/3] block: optimise boundary blkdev_read_iter's checks
Date: Wed, 20 Oct 2021 20:00:48 +0100 [thread overview]
Message-ID: <fff34e613aeaae1ad12977dc4592cb1a1f5d3190.1634755800.git.asml.silence@gmail.com> (raw)
In-Reply-To: <cover.1634755800.git.asml.silence@gmail.com>
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>
---
block/fops.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
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;
}
--
2.33.1
next prev parent reply other threads:[~2021-10-20 19:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-20 19:00 [PATCH 0/3] random simple block cleanups Pavel Begunkov
2021-10-20 19:00 ` Pavel Begunkov [this message]
2021-10-20 19:00 ` [PATCH 2/3] block: clean up blk_mq_submit_bio() merging Pavel Begunkov
2021-10-20 19:04 ` Pavel Begunkov
2021-10-21 8:30 ` Christoph Hellwig
2021-10-21 13:32 ` Pavel Begunkov
2021-10-20 19:00 ` [PATCH 3/3] block: convert fops.c magic constants to SHIFT_SECTOR Pavel Begunkov
2021-10-21 8:31 ` Christoph Hellwig
2021-10-21 14:27 ` [PATCH 0/3] random simple block cleanups Jens Axboe
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