block/blk-cgroup-fc-appid.c

   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  */
  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  */
  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);