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 1da3064311e255f26ceeb0690434a306e373a729..8f517888c3e10779ae551b0410b8d80760620436 100644 (file)
--- 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);