From 41af295b6d87609fadbd69ea1273b85f374af1a4 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 31 Jan 2019 10:41:54 +1100 Subject: [PATCH] BACKPORT: 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 Defenderault. 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: Johannes Weiner Signed-off-by: Suren Baghdasaryan Cc: Dennis Zhou Cc: Ingo Molnar Cc: Jens Axboe Cc: Li Zefan Cc: Peter Zijlstra Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell (cherry picked from commit: dc50537bdd1a0804fa2cbc990565ee9a944e66fa) Conflicts: include/linux/cgroup-Defenders.h kernel/cgroup.c (1. replaced __poll_t with unsigned int) Bug: 127712811 Test: lmkd in PSI mode Change-Id: I21aff1d9d31e3d4b45e257aa4d299405a2ce6de3 Signed-off-by: Suren Baghdasaryan --- include/linux/cgroup-defs.h | 4 ++++ kernel/cgroup/cgroup.c | 13 +++++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 41e670132df6..cc9e6a26829b 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -31,6 +31,7 @@ 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 @@ -502,6 +503,9 @@ struct cftype { ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off); + unsigned int (*poll)(struct kernfs_open_file *of, + struct poll_table_struct *pt); + #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lock_class_key lockdep_key; #endif diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index c9ae1cf12e48..01a8cf411f31 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -3473,6 +3473,17 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, return ret ?: nbytes; } +static unsigned int 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); @@ -3511,6 +3522,7 @@ 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, }; @@ -3519,6 +3531,7 @@ 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, -- 2.20.1