1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include "blk-cgroup.h"
4 
5 /**
6  * blkcg_set_fc_appid - set the fc_app_id field associted to blkcg
7  * @app_id: application identifier
8  * @cgrp_id: cgroup id
9  * @app_id_len: size of application identifier
10  */
blkcg_set_fc_appid(char * app_id,u64 cgrp_id,size_t app_id_len)11 int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len)
12 {
13 	struct cgroup *cgrp;
14 	struct cgroup_subsys_state *css;
15 	struct blkcg *blkcg;
16 	int ret  = 0;
17 
18 	if (app_id_len > FC_APPID_LEN)
19 		return -EINVAL;
20 
21 	cgrp = cgroup_get_from_id(cgrp_id);
22 	if (IS_ERR(cgrp))
23 		return PTR_ERR(cgrp);
24 	css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);
25 	if (!css) {
26 		ret = -ENOENT;
27 		goto out_cgrp_put;
28 	}
29 	blkcg = css_to_blkcg(css);
30 	/*
31 	 * There is a slight race condition on setting the appid.
32 	 * Worst case an I/O may not find the right id.
33 	 * This is no different from the I/O we let pass while obtaining
34 	 * the vmid from the fabric.
35 	 * Adding the overhead of a lock is not necessary.
36 	 */
37 	strscpy(blkcg->fc_app_id, app_id, app_id_len);
38 	css_put(css);
39 out_cgrp_put:
40 	cgroup_put(cgrp);
41 	return ret;
42 }
43 EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);
44 
45 /**
46  * blkcg_get_fc_appid - get the fc app identifier associated with a bio
47  * @bio: target bio
48  *
49  * On success return the fc_app_id, on failure return NULL
50  */
blkcg_get_fc_appid(struct bio * bio)51 char *blkcg_get_fc_appid(struct bio *bio)
52 {
53 	if (!bio->bi_blkg || bio->bi_blkg->blkcg->fc_app_id[0] == '\0')
54 		return NULL;
55 	return bio->bi_blkg->blkcg->fc_app_id;
56 }
57 EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);
58