linux-kernel - [PATCH] platform: goldfish: pipe: use get_user_pages

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Message-Id: <20161101194343.24072-1-lstoakes@gmail.com>
Date:   Tue,  1 Nov 2016 19:43:43 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH] platform: goldfish: pipe: use get_user_pages_unlocked()

Moving from get_user_pages() to get_user_pages_unlocked() simplifies the code
and takes advantage of VM_FAULT_RETRY functionality when faulting in pages.

Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index 1aba2c7..2b21033 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -308,10 +308,8 @@ static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
 		 * returns a small amount, then there's no need to pin that
 		 * much memory to the process.
 		 */
-		down_read(&current->mm->mmap_sem);
-		ret = get_user_pages(address, 1, is_write ? 0 : FOLL_WRITE,
-				&page, NULL);
-		up_read(&current->mm->mmap_sem);
+		ret = get_user_pages_unlocked(address, 1, &page,
+				is_write ? 0 : FOLL_WRITE);
 		if (ret < 0)
 			break;
 
-- 
2.10.2