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From 0f459ca8958fa9540a5aaca0f133f811028788b3 Mon Sep 17 00:00:00 2001
From: He Zhe <zhe.he@windriver.com>
Date: Fri, 8 Aug 2014 09:20:36 +0800
Subject: [PATCH 4/7] vm_cgroup: backport dependence to fix vm_cgroup mappings
accounting compile failure
Backport necessary dependence from v3.16-rc2 on which the original patch is
based on to fix compile failure.
- Backport css_tryget_online and percpu_ref_tryget_live for
get_vm_cgroup_from_task
- Change vm_cgrp_id to vm_subsys_id which is generated by
include/linux/cgroup.h
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
---
include/linux/cgroup.h | 17 +++++++++++++++++
include/linux/percpu-refcount.h | 33 +++++++++++++++++++++++++++++++++
mm/vm_cgroup.c | 2 +-
3 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 9450f025fe0c..b53d8043e296 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -121,6 +121,23 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
}
/**
+ * css_tryget_online - try to obtain a reference on the specified css if online
+ * @css: target css
+ *
+ * Obtain a reference on @css if it's online. The caller naturally needs
+ * to ensure that @css is accessible but doesn't have to be holding a
+ * reference on it - IOW, RCU protected access is good enough for this
+ * function. Returns %true if a reference count was successfully obtained;
+ * %false otherwise.
+ */
+static inline bool css_tryget_online(struct cgroup_subsys_state *css)
+{
+ if (css->flags & CSS_ROOT)
+ return true;
+ return percpu_ref_tryget_live(&css->refcnt);
+}
+
+/**
* css_put - put a css reference
* @css: target css
*
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 0afb48fd449d..35a242e24fbc 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -149,6 +149,39 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
}
/**
+ * percpu_ref_tryget_live - try to increment a live percpu refcount
+ * @ref: percpu_ref to try-get
+ *
+ * Increment a percpu refcount unless it has already been killed. Returns
+ * %true on success; %false on failure.
+ *
+ * Completion of percpu_ref_kill() in itself doesn't guarantee that tryget
+ * will fail. For such guarantee, percpu_ref_kill_and_confirm() should be
+ * used. After the confirm_kill callback is invoked, it's guaranteed that
+ * no new reference will be given out by percpu_ref_tryget().
+ *
+ * The caller is responsible for ensuring that @ref stays accessible.
+ */
+static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
+{
+ unsigned __percpu *pcpu_count;
+ int ret = false;
+
+ rcu_read_lock_sched();
+
+ pcpu_count = ACCESS_ONCE(ref->pcpu_count);
+
+ if (likely(REF_STATUS(pcpu_count) == PCPU_REF_PTR)) {
+ this_cpu_inc(*pcpu_count);
+ ret = true;
+ }
+
+ rcu_read_unlock_sched();
+
+ return ret;
+}
+
+/**
* percpu_ref_put - decrement a percpu refcount
* @ref: percpu_ref to put
*
diff --git a/mm/vm_cgroup.c b/mm/vm_cgroup.c
index 0d34ffcaf92e..10a24da2951a 100644
--- a/mm/vm_cgroup.c
+++ b/mm/vm_cgroup.c
@@ -28,7 +28,7 @@ static struct vm_cgroup *vm_cgroup_from_css(struct cgroup_subsys_state *s)
static struct vm_cgroup *vm_cgroup_from_task(struct task_struct *p)
{
- return vm_cgroup_from_css(task_css(p, vm_cgrp_id));
+ return vm_cgroup_from_css(task_css(p, vm_subsys_id));
}
static struct vm_cgroup *get_vm_cgroup_from_task(struct task_struct *p)
--
1.8.1.2
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