Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):

+/**
+ * cr_fill_fname - return pathname of a given file
+ * @path: path name
+ * @root: relative root
+ * @buf: buffer for pathname
+ * @n: buffer length (in) and pathname length (out)
+ */
+static char *
+cr_fill_fname(struct path *path, struct path *root, char *buf, int *n)
+{
+	struct path tmp = *root;
+	char *fname;
+
+	BUG_ON(!buf);
+	fname = __d_path(path, &tmp, buf, *n);
+	if (!IS_ERR(fname))
+		*n = (buf + (*n) - fname);
+	/*
+	 * FIXME: if __d_path() changed these, it must have stepped out of
+	 * init's namespace. Since currently we require a unified namespace
+	 * within the container: simply fail.
+	 */
+	if (tmp.mnt != root->mnt || tmp.dentry != root->dentry)
+		fname = ERR_PTR(-EBADF);

...

+static int cr_ctx_checkpoint(struct cr_ctx *ctx, pid_t pid)
+{
+	ctx->root_pid = pid;
+
+	/*
+	 * assume checkpointer is in container's root vfs
+	 * FIXME: this works for now, but will change with real containers
+	 */
+	ctx->vfsroot = &current->fs->root;
+	path_get(ctx->vfsroot);

Hi Oren,

Is there really any good reason to use current->fs->root rather
than ctx->root_task->fs->root here?

The way I'm testing, the checkpointer is in fact in a different
container, so the root passed into cr_fill_fname() is different
from the container's root, so cr_fill_fname() always returns me
-EBADF.

thanks,
-serge
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