cgroup: Homogenize cgroup_get_from_id() return value

Cgroup id is user provided datum hence extend its return domain to
include possible error reason (similar to cgroup_get_from_fd()).

This change also fixes commit d4ccaf58a847 ("bpf: Introduce cgroup
iter") that would use NULL instead of proper error handling in
d4ccaf58a847 ("bpf: Introduce cgroup iter").

Additionally, neither of: fc_appid_store, bpf_iter_attach_cgroup,
mem_cgroup_get_from_ino (callers of cgroup_get_from_fd) is built without
CONFIG_CGROUPS (depends via CONFIG_BLK_CGROUP, direct, transitive
CONFIG_MEMCG respectively) transitive, so drop the singular definition
not needed with !CONFIG_CGROUPS.

Fixes: d4ccaf58a847 ("bpf: Introduce cgroup iter")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c
index 760a2e1..842e5e1 100644 (file)
--- a/block/blk-cgroup-fc-appid.c
+++ b/block/blk-cgroup-fc-appid.c
@@ -19,8 +19,8 @@ int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len)
                return -EINVAL;
 
        cgrp = cgroup_get_from_id(cgrp_id);
-       if (!cgrp)
-               return -ENOENT;
+       if (IS_ERR(cgrp))
+               return PTR_ERR(cgrp);
        css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);
        if (!css) {
                ret = -ENOENT;

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 4d14372..30ee8ce 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -750,11 +750,6 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 
 static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 {}
-
-static inline struct cgroup *cgroup_get_from_id(u64 id)
-{
-       return NULL;
-}
 #endif /* !CONFIG_CGROUPS */
 
 #ifdef CONFIG_CGROUPS

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 3229f35..a8780ef 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6005,7 +6005,7 @@ void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 /*
  * cgroup_get_from_id : get the cgroup associated with cgroup id
  * @id: cgroup id
- * On success return the cgrp, on failure return NULL
+ * On success return the cgrp or ERR_PTR on failure
  * Only cgroups within current task's cgroup NS are valid.
  */
 struct cgroup *cgroup_get_from_id(u64 id)
@@ -6037,7 +6037,7 @@ struct cgroup *cgroup_get_from_id(u64 id)
                cgrp = NULL;
        }
 out:
-       return cgrp;
+       return cgrp ?: ERR_PTR(-ENOENT);
 }
 EXPORT_SYMBOL_GPL(cgroup_get_from_id);
 

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b69979c..86f5ca8 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5110,8 +5110,8 @@ struct mem_cgroup *mem_cgroup_get_from_ino(unsigned long ino)
        struct mem_cgroup *memcg;
 
        cgrp = cgroup_get_from_id(ino);
-       if (!cgrp)
-               return ERR_PTR(-ENOENT);
+       if (IS_ERR(cgrp))
+               return PTR_ERR(cgrp);
 
        css = cgroup_get_e_css(cgrp, &memory_cgrp_subsys);
        if (css)