fs/9p: call vmtruncate before setattr 9p opeation

We need to call vmtruncate before 9p setattr operation, otherwise we
could write back some dirty pages between setattr with ATTR_SIZE and vmtruncate
causing some truncated pages to be written back to server

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_inode.c

@@ -993,18 +993,16 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
 		if (iattr->ia_valid & ATTR_GID)
 			wstat.n_gid = iattr->ia_gid;
 	}
-
-	retval = p9_client_wstat(fid, &wstat);
-	if (retval < 0)
-		return retval;
-
-	v9fs_invalidate_inode_attr(dentry->d_inode);
 	if ((iattr->ia_valid & ATTR_SIZE) &&
 	    iattr->ia_size != i_size_read(dentry->d_inode)) {
 		retval = vmtruncate(dentry->d_inode, iattr->ia_size);
 		if (retval)
 			return retval;
 	}
+	retval = p9_client_wstat(fid, &wstat);
+	if (retval < 0)
+		return retval;
+	v9fs_invalidate_inode_attr(dentry->d_inode);
 
 	setattr_copy(dentry->d_inode, iattr);
 	mark_inode_dirty(dentry->d_inode);

fs/9p/vfs_inode_dotl.c

@@ -453,17 +453,16 @@ int v9fs_vfs_setattr_dotl(struct dentry *dentry, struct iattr *iattr)
 	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
-	retval = p9_client_setattr(fid, &p9attr);
-	if (retval < 0)
-		return retval;
-
-	v9fs_invalidate_inode_attr(dentry->d_inode);
 	if ((iattr->ia_valid & ATTR_SIZE) &&
 	    iattr->ia_size != i_size_read(dentry->d_inode)) {
 		retval = vmtruncate(dentry->d_inode, iattr->ia_size);
 		if (retval)
 			return retval;
 	}
+	retval = p9_client_setattr(fid, &p9attr);
+	if (retval < 0)
+		return retval;
+	v9fs_invalidate_inode_attr(dentry->d_inode);
 
 	setattr_copy(dentry->d_inode, iattr);
 	mark_inode_dirty(dentry->d_inode);