mm/memory-failure.c::hwpoison_filter_task() has been reaching into
cgroup to extract the associated ino to be used as a filtering
criterion. This is an implementation detail which shouldn't be
depended upon from outside cgroup proper and is about to change with
the scheduled kernfs conversion.
This patch introduces a proper interface to determine the associated
ino, cgroup_ino(), and updates hwpoison_filter_task() to use it
instead of reaching directly into cgroup.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
include/linux/cgroup.h | 9 +++++++++
kernel/cgroup.c | 5 ++++-
mm/memory-failure.c | 8 ++------
3 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 1e4f9e2..15b7839 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -505,6 +505,15 @@ static inline const char *cgroup_name(const struct cgroup *cgrp)
return rcu_dereference(cgrp->name)->name;
}
+/* returns ino associated with a cgroup, 0 indicates unmounted root */
+static inline ino_t cgroup_ino(struct cgroup *cgrp)
+{
+ if (cgrp->dentry)
+ return cgrp->dentry->d_inode->i_ino;
+ else
+ return 0;
+}
+
static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
{
struct cgroup_open_file *of = seq->private;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index bfbb207..e81e4c9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -792,7 +792,10 @@ static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
struct inode *inode = new_inode(sb);
if (inode) {
- inode->i_ino = get_next_ino();
+ do {
+ /* ino 0 is reserved for dummy_root */
+ inode->i_ino = get_next_ino();
+ } while (!inode->i_ino);
inode->i_mode = mode;
inode->i_uid = current_fsuid();
inode->i_gid = current_fsgid();
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 4f08a2d..9b5933c 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -145,14 +145,10 @@ static int hwpoison_filter_task(struct page *p)
return -EINVAL;
css = mem_cgroup_css(mem);
- /* root_mem_cgroup has NULL dentries */
- if (!css->cgroup->dentry)
- return -EINVAL;
-
- ino = css->cgroup->dentry->d_inode->i_ino;
+ ino = cgroup_ino(css->cgroup);
css_put(css);
- if (ino != hwpoison_filter_memcg)
+ if (!ino || ino != hwpoison_filter_memcg)
return -EINVAL;
return 0;
--
1.8.5.3
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