From: Kirill Tkhai <ktkhai@virtuozzo.com>
Date: Mon, 26 Nov 2018 09:46:20 +0000 (+0300)
Subject: fuse: Replace page without copying in fuse_writepage_in_flight()
X-Git-Tag: v5.1-rc1~50^2~20
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c5de16cca2d7268833abfd6456d73fbba447c19b;p=thirdparty%2Flinux.git

fuse: Replace page without copying in fuse_writepage_in_flight()

It looks like we can optimize page replacement and avoid copying by simple
updating the request's page.

[SzM: swap with new request's tmp page to avoid use after free.]

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ee59599f4947f..6b6e2574e7335 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1789,7 +1789,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
 		if (curr_index == page->index) {
 			WARN_ON(tmp->num_pages != 1);
 			WARN_ON(!test_bit(FR_PENDING, &tmp->flags));
-			copy_highpage(tmp->pages[0], page);
+			swap(tmp->pages[0], new_req->pages[0]);
 			break;
 		}
 	}