1 files changed, 57 insertions, 0 deletions
diff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c
new file mode 100644
index 000000000000..3ec21333f393
--- /dev/null
+++ b/block/blk-cgroup-fc-appid.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "blk-cgroup.h"
+
+/**
+ * blkcg_set_fc_appid - set the fc_app_id field associted to blkcg
+ * @app_id: application identifier
+ * @cgrp_id: cgroup id
+ * @app_id_len: size of application identifier
+ */
+int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len)
+{
+	struct cgroup *cgrp;
+	struct cgroup_subsys_state *css;
+	struct blkcg *blkcg;
+	int ret  = 0;
+
+	if (app_id_len > FC_APPID_LEN)
+		return -EINVAL;
+
+	cgrp = cgroup_get_from_id(cgrp_id);
+	if (IS_ERR(cgrp))
+		return PTR_ERR(cgrp);
+	css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);
+	if (!css) {
+		ret = -ENOENT;
+		goto out_cgrp_put;
+	}
+	blkcg = css_to_blkcg(css);
+	/*
+	 * There is a slight race condition on setting the appid.
+	 * Worst case an I/O may not find the right id.
+	 * This is no different from the I/O we let pass while obtaining
+	 * the vmid from the fabric.
+	 * Adding the overhead of a lock is not necessary.
+	 */
+	strscpy(blkcg->fc_app_id, app_id, app_id_len);
+	css_put(css);
+out_cgrp_put:
+	cgroup_put(cgrp);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);
+
+/**
+ * blkcg_get_fc_appid - get the fc app identifier associated with a bio
+ * @bio: target bio
+ *
+ * On success return the fc_app_id, on failure return NULL
+ */
+char *blkcg_get_fc_appid(struct bio *bio)
+{
+	if (!bio->bi_blkg || bio->bi_blkg->blkcg->fc_app_id[0] == '\0')
+		return NULL;
+	return bio->bi_blkg->blkcg->fc_app_id;
+}
+EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);