From f261c16861b82951bd2125706660ce4602930563 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Thu, 20 Aug 2020 11:34:10 +0300
Subject: [PATCH] io_uring: comment on kfree(iovec) checks
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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/io_uring.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d43a20a554e4c..b9ca5a54dc204 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;
--
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