pNFS: Ensure we layoutcommit before revalidating attributes

If we need to update the cached attributes, then we'd better make
sure that we also layoutcommit first. Otherwise, the server may have stale
attributes.

Prior to this patch, the revalidation code tried to "fix" this problem by
simply disabling attributes that would be affected by the layoutcommit.
That approach breaks nfs_writeback_check_extend(), leading to a file size
corruption.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/inode.c

@@ -974,6 +974,13 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 	if (NFS_STALE(inode))
 		goto out;
 
+	/* pNFS: Attributes aren't updated until we layoutcommit */
+	if (S_ISREG(inode->i_mode)) {
+		status = pnfs_sync_inode(inode, false);
+		if (status)
+			goto out;
+	}
+
 	status = -ENOMEM;
 	fattr = nfs_alloc_fattr();
 	if (fattr == NULL)
@@ -1493,28 +1500,12 @@ static int nfs_inode_attrs_need_update(const struct inode *inode, const struct n
 		((long)nfsi->attr_gencount - (long)nfs_read_attr_generation_counter() > 0);
 }
 
-/*
- * Don't trust the change_attribute, mtime, ctime or size if
- * a pnfs LAYOUTCOMMIT is outstanding
- */
-static void nfs_inode_attrs_handle_layoutcommit(struct inode *inode,
-		struct nfs_fattr *fattr)
-{
-	if (pnfs_layoutcommit_outstanding(inode))
-		fattr->valid &= ~(NFS_ATTR_FATTR_CHANGE |
-				NFS_ATTR_FATTR_MTIME |
-				NFS_ATTR_FATTR_CTIME |
-				NFS_ATTR_FATTR_SIZE);
-}
-
 static int nfs_refresh_inode_locked(struct inode *inode, struct nfs_fattr *fattr)
 {
 	int ret;
 
 	trace_nfs_refresh_inode_enter(inode);
 
-	nfs_inode_attrs_handle_layoutcommit(inode, fattr);
-
 	if (nfs_inode_attrs_need_update(inode, fattr))
 		ret = nfs_update_inode(inode, fattr);
 	else