teach shmem_get_link() to work in RCU mode

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

1 files changed, 14 insertions, 6 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 684dbc32e233..0605716aee06 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2501,12 +2501,20 @@ static const char *shmem_get_link(struct dentry *dentry,
 {
         struct page *page = NULL;
         int error;
-        if (!dentry)
-                return ERR_PTR(-ECHILD);
-        error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
-        if (error)
-                return ERR_PTR(error);
-        unlock_page(page);
+        if (!dentry) {
+                page = find_get_page(inode->i_mapping, 0);
+                if (!page)
+                        return ERR_PTR(-ECHILD);
+                if (!PageUptodate(page)) {
+                        put_page(page);
+                        return ERR_PTR(-ECHILD);
+                }
+        } else {
+                error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
+                if (error)
+                        return ERR_PTR(error);
+                unlock_page(page);
+        }
         *cookie = page;
         return page_address(page);
 }