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cgroup: use cgrp->kn->id as the cgroup ID

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cgroup ID is currently allocated using a dedicated per-hierarchy idr
and used internally and exposed through tracepoints and bpf.  This is
confusing because there are tracepoints and other interfaces which use
the cgroupfs ino as IDs.

The preceding changes made kn->id exposed as ino as 64bit ino on
supported archs or ino+gen (low 32bits as ino, high gen).  There's no
reason for cgroup to use different IDs.  The kernfs IDs are unique and
userland can easily discover them and map them back to paths using
standard file operations.

This patch replaces cgroup IDs with kernfs IDs.

* cgroup_id() is added and all cgroup ID users are converted to use it.

* kernfs_node creation is moved to earlier during cgroup init so that
  cgroup_id() is available during init.

* While at it, s/cgroup/cgrp/ in psi helpers for consistency.

* Fallback ID value is changed to 1 to be consistent with root cgroup
  ID.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Tejun Heo
2019-11-04 15:54:30 -08:00
parent 40430452fd
commit 743210386c
8 changed files with 43 additions and 85 deletions
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kernel/trace/blktrace.c
+2 -2
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@@ -171,7 +171,7 @@ void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
blkcg = NULL;
#ifdef CONFIG_BLK_CGROUP
trace_note(bt, 0, BLK_TN_MESSAGE, buf, n,
blkcg ? cgroup_get_kernfs_id(blkcg->css.cgroup) : 0);
blkcg ? cgroup_id(blkcg->css.cgroup) : 1);
#else
trace_note(bt, 0, BLK_TN_MESSAGE, buf, n, 0);
#endif
@@ -759,7 +759,7 @@ static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
if (!bio->bi_blkg)
return 0;
return cgroup_get_kernfs_id(bio_blkcg(bio)->css.cgroup);
return cgroup_id(bio_blkcg(bio)->css.cgroup);
}
#else
u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)