113 lines
3.4 KiB
Diff
113 lines
3.4 KiB
Diff
From 3b4d888114a5f6c1e848f892a2236db4ccf8345f Mon Sep 17 00:00:00 2001
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From: Angelo Ruocco <angeloruocco90@gmail.com>
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Date: Tue, 21 May 2019 10:01:54 +0200
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Subject: [PATCH] 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
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points to the file associated with the cftype.
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Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
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Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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(cherry picked from commit 54b7b868e826b294687c439b68ec55fe20cafe5b)
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Signed-off-by: Li Yang <leoyang.li@nxp.com>
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---
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include/linux/cgroup-defs.h | 3 +++
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kernel/cgroup/cgroup.c | 33 +++++++++++++++++++++++++++++----
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2 files changed, 32 insertions(+), 4 deletions(-)
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--- a/include/linux/cgroup-defs.h
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+++ b/include/linux/cgroup-defs.h
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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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+
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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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@@ -544,6 +546,7 @@ 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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--- a/kernel/cgroup/cgroup.c
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+++ b/kernel/cgroup/cgroup.c
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@@ -1465,8 +1465,8 @@ struct cgroup *task_cgroup_from_root(str
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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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@@ -1476,13 +1476,26 @@ static char *cgroup_file_name(struct cgr
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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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+
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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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/**
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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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@@ -1641,6 +1654,9 @@ static void cgroup_rm_file(struct cgroup
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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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@@ -3896,6 +3912,7 @@ static int cgroup_add_file(struct cgroup
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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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@@ -3926,6 +3943,14 @@ static int cgroup_add_file(struct cgroup
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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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+
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return 0;
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}
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