[PATCH] io_uring: comment on kfree(iovec) checks

[Pavel Begunkov <asml.silence@gmail.com>]

kfree() handles NULL pointers well, but io_{read,write}() checks it
because of performance reasons. Leave a comment there for those who are
tempted to patch it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 938112826dd1..ea2d1cb5c422 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3204,6 +3204,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 	kiocb_done(kiocb, ret, cs);
 	ret = 0;
 out_free:
+	/* it's reportedly faster than delegating the null check to kfree() */
 	if (iovec)
 		kfree(iovec);
 	return ret;
@@ -3300,6 +3301,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
 			return -EAGAIN;
 	}
 out_free:
+	/* it's reportedly faster than delegating the null check to kfree() */
 	if (iovec)
 		kfree(iovec);
 	return ret;
-- 
2.24.0