target/linux/layerscape/patches-5.4/303-core-0003-cgroup-let-a-symlink-too-be-created-with-a-cftype-fi.patch

   1 From 3b4d888114a5f6c1e848f892a2236db4ccf8345f Mon Sep 17 00:00:00 2001
   2 From: Angelo Ruocco <angeloruocco90@gmail.com>
   3 Date: Tue, 21 May 2019 10:01:54 +0200
   4 Subject: [PATCH] cgroup: let a symlink too be created with a cftype file
   5
   6 This commit enables a cftype to have a symlink (of any name) that
   7 points to the file associated with the cftype.
   8
   9 Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
  10 Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
  11 Signed-off-by: Jens Axboe <axboe@kernel.dk>
  12 (cherry picked from commit 54b7b868e826b294687c439b68ec55fe20cafe5b)
  13 Signed-off-by: Li Yang <leoyang.li@nxp.com>
  14 ---
  15  include/linux/cgroup-defs.h |  3 +++
  16  kernel/cgroup/cgroup.c      | 33 +++++++++++++++++++++++++++++----
  17  2 files changed, 32 insertions(+), 4 deletions(-)
  18
  19 --- a/include/linux/cgroup-defs.h
  20 +++ b/include/linux/cgroup-defs.h
  21 @@ -106,6 +106,8 @@ enum {
  22         CFTYPE_WORLD_WRITABLE   = (1 << 4),     /* (DON'T USE FOR NEW FILES) S_IWUGO */
  23         CFTYPE_DEBUG            = (1 << 5),     /* create when cgroup_debug */
  24
  25 +       CFTYPE_SYMLINKED        = (1 << 6),     /* pointed to by symlink too */
  26 +
  27         /* internal flags, do not use outside cgroup core proper */
  28         __CFTYPE_ONLY_ON_DFL    = (1 << 16),    /* only on default hierarchy */
  29         __CFTYPE_NOT_ON_DFL     = (1 << 17),    /* not on default hierarchy */
  30 @@ -544,6 +546,7 @@ struct cftype {
  31          * end of cftype array.
  32          */
  33         char name[MAX_CFTYPE_NAME];
  34 +       char link_name[MAX_CFTYPE_NAME];
  35         unsigned long private;
  36
  37         /*
  38 --- a/kernel/cgroup/cgroup.c
  39 +++ b/kernel/cgroup/cgroup.c
  40 @@ -1465,8 +1465,8 @@ struct cgroup *task_cgroup_from_root(str
  41
  42  static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
  43
  44 -static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
  45 -                             char *buf)
  46 +static char *cgroup_fill_name(struct cgroup *cgrp, const struct cftype *cft,
  47 +                             char *buf, bool write_link_name)
  48  {
  49         struct cgroup_subsys *ss = cft->ss;
  50
  51 @@ -1476,13 +1476,26 @@ static char *cgroup_file_name(struct cgr
  52
  53                 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
  54                          dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
  55 -                        cft->name);
  56 +                        write_link_name ? cft->link_name : cft->name);
  57         } else {
  58 -               strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
  59 +               strscpy(buf, write_link_name ? cft->link_name : cft->name,
  60 +                       CGROUP_FILE_NAME_MAX);
  61         }
  62         return buf;
  63  }
  64
  65 +static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
  66 +                             char *buf)
  67 +{
  68 +       return cgroup_fill_name(cgrp, cft, buf, false);
  69 +}
  70 +
  71 +static char *cgroup_link_name(struct cgroup *cgrp, const struct cftype *cft,
  72 +                             char *buf)
  73 +{
  74 +       return cgroup_fill_name(cgrp, cft, buf, true);
  75 +}
  76 +
  77  /**
  78   * cgroup_file_mode - deduce file mode of a control file
  79   * @cft: the control file in question
  80 @@ -1641,6 +1654,9 @@ static void cgroup_rm_file(struct cgroup
  81         }
  82
  83         kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
  84 +       if (cft->flags & CFTYPE_SYMLINKED)
  85 +               kernfs_remove_by_name(cgrp->kn,
  86 +                                     cgroup_link_name(cgrp, cft, name));
  87  }
  88
  89  /**
  90 @@ -3873,6 +3889,7 @@ static int cgroup_add_file(struct cgroup
  91  {
  92         char name[CGROUP_FILE_NAME_MAX];
  93         struct kernfs_node *kn;
  94 +       struct kernfs_node *kn_link;
  95         struct lock_class_key *key = NULL;
  96         int ret;
  97
  98 @@ -3903,6 +3920,14 @@ static int cgroup_add_file(struct cgroup
  99                 spin_unlock_irq(&cgroup_file_kn_lock);
 100         }
 101
 102 +       if (cft->flags & CFTYPE_SYMLINKED) {
 103 +               kn_link = kernfs_create_link(cgrp->kn,
 104 +                                            cgroup_link_name(cgrp, cft, name),
 105 +                                            kn);
 106 +               if (IS_ERR(kn_link))
 107 +                       return PTR_ERR(kn_link);
 108 +       }
 109 +
 110         return 0;
 111  }
 112