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 <angeloruocco90@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -106,6 +106,8 @@ enum {
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CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
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CFTYPE_DEBUG = (1 << 5), /* create when cgroup_debug */
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CFTYPE_SYMLINKED = (1 << 6), /* pointed to by symlink too */
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/* internal flags, do not use outside cgroup core proper */
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__CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
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__CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
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@ -543,6 +545,7 @@ struct cftype {
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* end of cftype array.
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*/
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char name[MAX_CFTYPE_NAME];
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char link_name[MAX_CFTYPE_NAME];
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unsigned long private;
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/*
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@ -1460,8 +1460,8 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task,
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static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
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static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
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char *buf)
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static char *cgroup_fill_name(struct cgroup *cgrp, const struct cftype *cft,
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char *buf, bool write_link_name)
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{
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struct cgroup_subsys *ss = cft->ss;
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@ -1471,13 +1471,26 @@ static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
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snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
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dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
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cft->name);
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write_link_name ? cft->link_name : cft->name);
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} else {
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strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
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strscpy(buf, write_link_name ? cft->link_name : cft->name,
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CGROUP_FILE_NAME_MAX);
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}
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return buf;
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}
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static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
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char *buf)
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{
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return cgroup_fill_name(cgrp, cft, buf, false);
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}
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static char *cgroup_link_name(struct cgroup *cgrp, const struct cftype *cft,
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char *buf)
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{
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return cgroup_fill_name(cgrp, cft, buf, true);
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}
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/**
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* cgroup_file_mode - deduce file mode of a control file
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* @cft: the control file in question
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@ -1636,6 +1649,9 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
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}
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kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
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if (cft->flags & CFTYPE_SYMLINKED)
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kernfs_remove_by_name(cgrp->kn,
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cgroup_link_name(cgrp, cft, name));
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}
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/**
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@ -3821,6 +3837,7 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
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{
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char name[CGROUP_FILE_NAME_MAX];
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struct kernfs_node *kn;
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struct kernfs_node *kn_link;
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struct lock_class_key *key = NULL;
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int ret;
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@ -3851,6 +3868,14 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
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spin_unlock_irq(&cgroup_file_kn_lock);
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}
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if (cft->flags & CFTYPE_SYMLINKED) {
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kn_link = kernfs_create_link(cgrp->kn,
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cgroup_link_name(cgrp, cft, name),
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kn);
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if (IS_ERR(kn_link))
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return PTR_ERR(kn_link);
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}
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return 0;
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}
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