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cgroup: let a symlink too be created with a cftype file

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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 <angeloruocco90@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Angelo Ruocco 2019-05-21 10:01:54 +02:00 committed by Jens Axboe
parent c3e2219216
commit 54b7b868e8
2 changed files with 32 additions and 4 deletions
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3
include/linux/cgroup-defs.h
View file

@ -106,6 +106,8 @@ enum {
CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
CFTYPE_DEBUG = (1 << 5), /* create when cgroup_debug */
CFTYPE_SYMLINKED = (1 << 6), /* pointed to by symlink too */
/* internal flags, do not use outside cgroup core proper */
__CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
__CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
@ -543,6 +545,7 @@ struct cftype {
* end of cftype array.
*/
char name[MAX_CFTYPE_NAME];
char link_name[MAX_CFTYPE_NAME];
unsigned long private;
/*

33
kernel/cgroup/cgroup.c
View file

@ -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;
}