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>

1 files changed, 13 insertions, 6 deletions

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);