teach nfs_get_link() to work in RCU mode

based upon the corresponding patch from Neil's March patchset,
again with kmap-related horrors removed.

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

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index ae9aa0b..aa828e8 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1087,6 +1087,27 @@ static bool nfs_mapping_need_revalidate_inode(struct inode *inode)
                || NFS_STALE(inode);
 }
 
+int nfs_revalidate_mapping_rcu(struct inode *inode)
+{
+       struct nfs_inode *nfsi = NFS_I(inode);
+       unsigned long *bitlock = &nfsi->flags;
+       int ret = 0;
+
+       if (IS_SWAPFILE(inode))
+               goto out;
+       if (nfs_mapping_need_revalidate_inode(inode)) {
+               ret = -ECHILD;
+               goto out;
+       }
+       spin_lock(&inode->i_lock);
+       if (test_bit(NFS_INO_INVALIDATING, bitlock) ||
+           (nfsi->cache_validity & NFS_INO_INVALID_DATA))
+               ret = -ECHILD;
+       spin_unlock(&inode->i_lock);
+out:
+       return ret;
+}
+
 /**
  * __nfs_revalidate_mapping - Revalidate the pagecache
  * @inode - pointer to host inode

diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 8ade8a8..95c69af 100644 (file)
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -48,16 +48,26 @@ static const char *nfs_get_link(struct dentry *dentry,
        struct page *page;
        void *err;
 
-       if (!dentry)
-               return ERR_PTR(-ECHILD);
-
-       err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
-       if (err)
-               return err;
-       page = read_cache_page(&inode->i_data, 0,
-                               (filler_t *)nfs_symlink_filler, inode);
-       if (IS_ERR(page))
-               return ERR_CAST(page);
+       if (!dentry) {
+               err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
+               if (err)
+                       return err;
+               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 {
+               err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
+               if (err)
+                       return err;
+               page = read_cache_page(&inode->i_data, 0,
+                                       (filler_t *)nfs_symlink_filler, inode);
+               if (IS_ERR(page))
+                       return ERR_CAST(page);
+       }
        *cookie = page;
        return page_address(page);
 }

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c0e9614..37a3d29 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -359,6 +359,7 @@ extern int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode);
 extern int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *inode);
 extern int __nfs_revalidate_inode(struct nfs_server *, struct inode *);
 extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);
+extern int nfs_revalidate_mapping_rcu(struct inode *inode);
 extern int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *mapping);
 extern int nfs_setattr(struct dentry *, struct iattr *);
 extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);