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Subject: [PATCH 2/2] fuse: Replace page without copying in
 fuse_writepage_in_flight()
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
To:     miklos@szeredi.hu, ktkhai@virtuozzo.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 26 Nov 2018 12:46:20 +0300
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It looks like we can optimize old_req page replacement
and avoid copying by simple updating the request's page.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 fs/fuse/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c6650c68b31a..83b54b082c86 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1778,7 +1778,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
 	if (old_req->num_pages == 1 && old_req != first_req) {
 		struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host);
 
-		copy_highpage(old_req->pages[0], page);
+		swap(old_req->pages[0], page);
 		spin_unlock(&fc->lock);
 
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);