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-rw-r--r--kernel/cgroup.c43
1 files changed, 32 insertions, 11 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c4bc8da..583f8f6 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2277,6 +2277,17 @@ static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft,
return 0;
}
+/* return the css for the given cgroup file */
+static struct cgroup_subsys_state *cgroup_file_css(struct cfent *cfe)
+{
+ struct cftype *cft = cfe->type;
+ struct cgroup *cgrp = __d_cgrp(cfe->dentry->d_parent);
+
+ if (cft->ss)
+ return cgrp->subsys[cft->ss->subsys_id];
+ return NULL;
+}
+
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64
@@ -2354,8 +2365,6 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
- if (cgroup_is_dead(cgrp))
- return -ENODEV;
if (cft->write)
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
if (cft->write_u64 || cft->write_s64)
@@ -2399,9 +2408,6 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf,
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
- if (cgroup_is_dead(cgrp))
- return -ENODEV;
-
if (cft->read)
return cft->read(cgrp, cft, file, buf, nbytes, ppos);
if (cft->read_u64)
@@ -2447,15 +2453,22 @@ static const struct file_operations cgroup_seqfile_operations = {
static int cgroup_file_open(struct inode *inode, struct file *file)
{
+ struct cfent *cfe = __d_cfe(file->f_dentry);
+ struct cftype *cft = __d_cft(file->f_dentry);
+ struct cgroup_subsys_state *css = cgroup_file_css(cfe);
int err;
- struct cfent *cfe;
- struct cftype *cft;
err = generic_file_open(inode, file);
if (err)
return err;
- cfe = __d_cfe(file->f_dentry);
- cft = cfe->type;
+
+ /*
+ * If the file belongs to a subsystem, pin the css. Will be
+ * unpinned either on open failure or release. This ensures that
+ * @css stays alive for all file operations.
+ */
+ if (css && !css_tryget(css))
+ return -ENODEV;
if (cft->read_map || cft->read_seq_string) {
file->f_op = &cgroup_seqfile_operations;
@@ -2464,15 +2477,23 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
err = cft->open(inode, file);
}
+ if (css && err)
+ css_put(css);
return err;
}
static int cgroup_file_release(struct inode *inode, struct file *file)
{
+ struct cfent *cfe = __d_cfe(file->f_dentry);
struct cftype *cft = __d_cft(file->f_dentry);
+ struct cgroup_subsys_state *css = cgroup_file_css(cfe);
+ int ret = 0;
+
if (cft->release)
- return cft->release(inode, file);
- return 0;
+ ret = cft->release(inode, file);
+ if (css)
+ css_put(css);
+ return ret;
}
/*
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