cgroup: pass around cgroup_subsys_state instead of cgroup in file methods

cgroup is currently in the process of transitioning to using struct
cgroup_subsys_state * as the primary handle instead of struct cgroup.
Please see the previous commit which converts the subsystem methods
for rationale.

This patch converts all cftype file operations to take @css instead of
@cgroup.  cftypes for the cgroup core files don't have their subsytem
pointer set.  These will automatically use the dummy_css added by the
previous patch and can be converted the same way.

Most subsystem conversions are straight forwards but there are some
interesting ones.

* freezer: update_if_frozen() is also converted to take @css instead
  of @cgroup for consistency.  This will make the code look simpler
  too once iterators are converted to use css.

* memory/vmpressure: mem_cgroup_from_css() needs to be exported to
  vmpressure while mem_cgroup_from_cont() can be made static.
  Updated accordingly.

* cpu: cgroup_tg() doesn't have any user left.  Removed.

* cpuacct: cgroup_ca() doesn't have any user left.  Removed.

* hugetlb: hugetlb_cgroup_form_cgroup() doesn't have any user left.
  Removed.

* net_cls: cgrp_cls_state() doesn't have any user left.  Removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 14 insertions, 12 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b0d5f53ae5e1..0b91436c68ef 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -439,34 +439,34 @@ struct cftype {
 	struct cgroup_subsys *ss;
 
 	int (*open)(struct inode *inode, struct file *file);
-	ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
+	ssize_t (*read)(struct cgroup_subsys_state *css, struct cftype *cft,
 			struct file *file,
 			char __user *buf, size_t nbytes, loff_t *ppos);
 	/*
 	 * read_u64() is a shortcut for the common case of returning a
 	 * single integer. Use it in place of read()
 	 */
-	u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
+	u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
 	/*
 	 * read_s64() is a signed version of read_u64()
 	 */
-	s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
+	s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
 	/*
 	 * read_map() is used for defining a map of key/value
 	 * pairs. It should call cb->fill(cb, key, value) for each
 	 * entry. The key/value pairs (and their ordering) should not
 	 * change between reboots.
 	 */
-	int (*read_map)(struct cgroup *cgrp, struct cftype *cft,
+	int (*read_map)(struct cgroup_subsys_state *css, struct cftype *cft,
 			struct cgroup_map_cb *cb);
 	/*
 	 * read_seq_string() is used for outputting a simple sequence
 	 * using seqfile.
 	 */
-	int (*read_seq_string)(struct cgroup *cgrp, struct cftype *cft,
-			       struct seq_file *m);
+	int (*read_seq_string)(struct cgroup_subsys_state *css,
+			       struct cftype *cft, struct seq_file *m);
 
-	ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
+	ssize_t (*write)(struct cgroup_subsys_state *css, struct cftype *cft,
 			 struct file *file,
 			 const char __user *buf, size_t nbytes, loff_t *ppos);
 
@@ -475,18 +475,20 @@ struct cftype {
 	 * a single integer (as parsed by simple_strtoull) from
 	 * userspace. Use in place of write(); return 0 or error.
 	 */
-	int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
+	int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
+			 u64 val);
 	/*
 	 * write_s64() is a signed version of write_u64()
 	 */
-	int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
+	int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
+			 s64 val);
 
 	/*
 	 * write_string() is passed a nul-terminated kernelspace
 	 * buffer of maximum length determined by max_write_len.
 	 * Returns 0 or -ve error code.
 	 */
-	int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
+	int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft,
 			    const char *buffer);
 	/*
 	 * trigger() callback can be used to get some kick from the
@@ -494,7 +496,7 @@ struct cftype {
 	 * at all. The private field can be used to determine the
 	 * kick type for multiplexing.
 	 */
-	int (*trigger)(struct cgroup *cgrp, unsigned int event);
+	int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
 
 	int (*release)(struct inode *inode, struct file *file);
 
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 7b4d9d79570b..6c416092e324 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -85,7 +85,7 @@ extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 extern struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm);
 
 extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
-extern struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont);
+extern struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css);
 
 static inline
 bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg)