From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 17 Nov 2015 15:41:04 +0000 (-0500)
Subject: teach page_get_link() to work in RCU mode
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d3883d4f93449343be6296e2274360db39b6842a;p=linux-beck.git

teach page_get_link() to work in RCU mode

more or less along the lines of Neil's patchset, sans the insanity
around kmap().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/namei.c b/fs/namei.c
index 1da3064311e2..8f517888c3e1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4533,12 +4533,19 @@ const char *page_get_link(struct dentry *dentry, struct inode *inode,
 	struct page *page;
 	struct address_space *mapping = inode->i_mapping;
 
-	if (!dentry)
-		return ERR_PTR(-ECHILD);
-
-	page = read_mapping_page(mapping, 0, NULL);
-	if (IS_ERR(page))
-		return (char*)page;
+	if (!dentry) {
+		page = find_get_page(mapping, 0);
+		if (!page)
+			return ERR_PTR(-ECHILD);
+		if (!PageUptodate(page)) {
+			put_page(page);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		page = read_mapping_page(mapping, 0, NULL);
+		if (IS_ERR(page))
+			return (char*)page;
+	}
 	*cookie = page;
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
 	kaddr = page_address(page);