Commit dc50537b authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

kernel: cgroup: add poll file operation 

Cgroup has a standardized poll/notification mechanism for waking all
pollers on all fds when a filesystem node changes.  To allow polling for
custom events, add a .poll callback that can override the default.

This is in preparation for pollable cgroup pressure files which have
per-fd trigger configurations.

Link: http://lkml.kernel.org/r/20190124211518.244221-3-surenb@google.com


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 147e1a97

include/linux/cgroup-defs.h

+4 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ struct kernfs_node; 
struct kernfs_ops;

struct kernfs_open_file;

struct seq_file;

struct poll_table_struct;



#define MAX_CGROUP_TYPE_NAMELEN 32

#define MAX_CGROUP_ROOT_NAMELEN 64
@@ -574,6 +575,9 @@ struct cftype { 
	ssize_t (*write)(struct kernfs_open_file *of,

			 char *buf, size_t nbytes, loff_t off);



	__poll_t (*poll)(struct kernfs_open_file *of,

			 struct poll_table_struct *pt);



#ifdef CONFIG_DEBUG_LOCK_ALLOC

	struct lock_class_key	lockdep_key;

#endif

kernel/cgroup/cgroup.c

+12 −0
Original line number Diff line number Diff line
@@ -3534,6 +3534,16 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, 
	return ret ?: nbytes;

}



static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)

{

	struct cftype *cft = of->kn->priv;



	if (cft->poll)

		return cft->poll(of, pt);



	return kernfs_generic_poll(of, pt);

}



static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)

{

	return seq_cft(seq)->seq_start(seq, ppos);
@@ -3572,6 +3582,7 @@ static struct kernfs_ops cgroup_kf_single_ops = { 
	.open			= cgroup_file_open,

	.release		= cgroup_file_release,

	.write			= cgroup_file_write,

	.poll			= cgroup_file_poll,

	.seq_show		= cgroup_seqfile_show,

};
@@ -3580,6 +3591,7 @@ static struct kernfs_ops cgroup_kf_ops = { 
	.open			= cgroup_file_open,

	.release		= cgroup_file_release,

	.write			= cgroup_file_write,

	.poll			= cgroup_file_poll,

	.seq_start		= cgroup_seqfile_start,

	.seq_next		= cgroup_seqfile_next,

	.seq_stop		= cgroup_seqfile_stop,

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