From 54b7b868e826b294687c439b68ec55fe20cafe5b Mon Sep 17 00:00:00 2001 From: Angelo Ruocco Date: Tue, 21 May 2019 10:01:54 +0200 Subject: cgroup: let a symlink too be created with a cftype file This commit enables a cftype to have a symlink (of any name) that points to the file associated with the cftype. Signed-off-by: Angelo Ruocco Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- kernel/cgroup/cgroup.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 426a0026225c..155048b0eca2 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1460,8 +1460,8 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task, static struct kernfs_syscall_ops cgroup_kf_syscall_ops; -static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft, - char *buf) +static char *cgroup_fill_name(struct cgroup *cgrp, const struct cftype *cft, + char *buf, bool write_link_name) { struct cgroup_subsys *ss = cft->ss; @@ -1471,13 +1471,26 @@ static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft, snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s", dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name, - cft->name); + write_link_name ? cft->link_name : cft->name); } else { - strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX); + strscpy(buf, write_link_name ? cft->link_name : cft->name, + CGROUP_FILE_NAME_MAX); } return buf; } +static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft, + char *buf) +{ + return cgroup_fill_name(cgrp, cft, buf, false); +} + +static char *cgroup_link_name(struct cgroup *cgrp, const struct cftype *cft, + char *buf) +{ + return cgroup_fill_name(cgrp, cft, buf, true); +} + /** * cgroup_file_mode - deduce file mode of a control file * @cft: the control file in question @@ -1636,6 +1649,9 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) } kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name)); + if (cft->flags & CFTYPE_SYMLINKED) + kernfs_remove_by_name(cgrp->kn, + cgroup_link_name(cgrp, cft, name)); } /** @@ -3821,6 +3837,7 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp, { char name[CGROUP_FILE_NAME_MAX]; struct kernfs_node *kn; + struct kernfs_node *kn_link; struct lock_class_key *key = NULL; int ret; @@ -3851,6 +3868,14 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp, spin_unlock_irq(&cgroup_file_kn_lock); } + if (cft->flags & CFTYPE_SYMLINKED) { + kn_link = kernfs_create_link(cgrp->kn, + cgroup_link_name(cgrp, cft, name), + kn); + if (IS_ERR(kn_link)) + return PTR_ERR(kn_link); + } + return 0; } -- cgit