[Devel] [PATCH RHEL7 COMMIT] ms/relay: Use per CPU constructs for the relay channel buffer pointers
Konstantin Khorenko
khorenko at virtuozzo.com
Wed May 16 11:09:24 MSK 2018
The commit is pushed to "branch-rh7-3.10.0-693.21.1.vz7.47.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.21.1.vz7.47.6
------>
commit 604a06c4e7992833e0b58c8b7b153de894680330
Author: Akash Goel <akash.goel at intel.com>
Date: Wed May 16 11:09:23 2018 +0300
ms/relay: Use per CPU constructs for the relay channel buffer pointers
relay essentially needs to maintain a per CPU array of channel buffer
pointers but it manually creates that array. Instead its better to use
the per CPU constructs, provided by the kernel, to allocate & access the
array of pointer to channel buffers.
Signed-off-by: Akash Goel <akash.goel at intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Link: http://lkml.kernel.org/r/1470909140-25919-1-git-send-email-akash.goel@intel.com
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
ms commit 017c59c042d01fc84cae7a8ea475861e702c77ab
https://jira.sw.ru/browse/HCI-53
Signed-off-by: Oleg Babin <obabin at virtuozzo.com>
---
include/linux/relay.h | 17 +++++++-----
kernel/relay.c | 74 +++++++++++++++++++++++++++++----------------------
2 files changed, 52 insertions(+), 39 deletions(-)
diff --git a/include/linux/relay.h b/include/linux/relay.h
index d7c8359693c6..eb295e373b90 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -19,6 +19,7 @@
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
+#include <linux/percpu.h>
/*
* Tracks changes to rchan/rchan_buf structs
@@ -63,7 +64,7 @@ struct rchan
struct kref kref; /* channel refcount */
void *private_data; /* for user-defined data */
size_t last_toobig; /* tried to log event > subbuf size */
- struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+ struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
int is_global; /* One global buffer ? */
struct list_head list; /* for channel list */
struct dentry *parent; /* parent dentry passed to open */
@@ -204,7 +205,7 @@ static inline void relay_write(struct rchan *chan,
struct rchan_buf *buf;
local_irq_save(flags);
- buf = chan->buf[smp_processor_id()];
+ buf = *this_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
@@ -230,12 +231,12 @@ static inline void __relay_write(struct rchan *chan,
{
struct rchan_buf *buf;
- buf = chan->buf[get_cpu()];
+ buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
buf->offset += length;
- put_cpu();
+ put_cpu_ptr(chan->buf);
}
/**
@@ -251,17 +252,19 @@ static inline void __relay_write(struct rchan *chan,
*/
static inline void *relay_reserve(struct rchan *chan, size_t length)
{
- void *reserved;
- struct rchan_buf *buf = chan->buf[smp_processor_id()];
+ void *reserved = NULL;
+ struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
length = relay_switch_subbuf(buf, length);
if (!length)
- return NULL;
+ goto end;
}
reserved = buf->data + buf->offset;
buf->offset += length;
+end:
+ put_cpu_ptr(chan->buf);
return reserved;
}
diff --git a/kernel/relay.c b/kernel/relay.c
index 1b2a7dc44fd9..b848f04f0cd7 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -217,7 +217,7 @@ static void relay_destroy_buf(struct rchan_buf *buf)
__free_page(buf->page_array[i]);
relay_free_page_array(buf->page_array);
}
- chan->buf[buf->cpu] = NULL;
+ *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
kfree(buf->padding);
kfree(buf);
kref_put(&chan->kref, relay_destroy_channel);
@@ -385,20 +385,21 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
*/
void relay_reset(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
- if (chan->is_global && chan->buf[0]) {
- __relay_reset(chan->buf[0], 0);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
+ __relay_reset(buf, 0);
return;
}
mutex_lock(&relay_channels_mutex);
for_each_possible_cpu(i)
- if (chan->buf[i])
- __relay_reset(chan->buf[i], 0);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ __relay_reset(buf, 0);
mutex_unlock(&relay_channels_mutex);
}
EXPORT_SYMBOL_GPL(relay_reset);
@@ -443,7 +444,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
struct dentry *dentry;
if (chan->is_global)
- return chan->buf[0];
+ return *per_cpu_ptr(chan->buf, 0);
buf = relay_create_buf(chan);
if (!buf)
@@ -467,7 +468,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
__relay_reset(buf, 1);
if(chan->is_global) {
- chan->buf[0] = buf;
+ *per_cpu_ptr(chan->buf, 0) = buf;
buf->cpu = 0;
}
@@ -529,22 +530,24 @@ static int relay_hotcpu_callback(struct notifier_block *nb,
{
unsigned int hotcpu = (unsigned long)hcpu;
struct rchan *chan;
+ struct rchan_buf *buf;
switch(action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
mutex_lock(&relay_channels_mutex);
list_for_each_entry(chan, &relay_channels, list) {
- if (chan->buf[hotcpu])
+ if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
continue;
- chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
- if(!chan->buf[hotcpu]) {
+ buf = relay_open_buf(chan, hotcpu);
+ if (!buf) {
printk(KERN_ERR
"relay_hotcpu_callback: cpu %d buffer "
"creation failed\n", hotcpu);
mutex_unlock(&relay_channels_mutex);
return notifier_from_errno(-ENOMEM);
}
+ *per_cpu_ptr(chan->buf, hotcpu) = buf;
}
mutex_unlock(&relay_channels_mutex);
break;
@@ -586,6 +589,7 @@ struct rchan *relay_open(const char *base_filename,
{
unsigned int i;
struct rchan *chan;
+ struct rchan_buf *buf;
if (!(subbuf_size && n_subbufs))
return NULL;
@@ -596,6 +600,7 @@ struct rchan *relay_open(const char *base_filename,
if (!chan)
return NULL;
+ chan->buf = alloc_percpu(struct rchan_buf *);
chan->version = RELAYFS_CHANNEL_VERSION;
chan->n_subbufs = n_subbufs;
chan->subbuf_size = subbuf_size;
@@ -611,9 +616,10 @@ struct rchan *relay_open(const char *base_filename,
mutex_lock(&relay_channels_mutex);
for_each_online_cpu(i) {
- chan->buf[i] = relay_open_buf(chan, i);
- if (!chan->buf[i])
+ buf = relay_open_buf(chan, i);
+ if (!buf)
goto free_bufs;
+ *per_cpu_ptr(chan->buf, i) = buf;
}
list_add(&chan->list, &relay_channels);
mutex_unlock(&relay_channels_mutex);
@@ -622,8 +628,8 @@ struct rchan *relay_open(const char *base_filename,
free_bufs:
for_each_possible_cpu(i) {
- if (chan->buf[i])
- relay_close_buf(chan->buf[i]);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_close_buf(buf);
}
kref_put(&chan->kref, relay_destroy_channel);
@@ -668,6 +674,7 @@ int relay_late_setup_files(struct rchan *chan,
unsigned int i, curr_cpu;
unsigned long flags;
struct dentry *dentry;
+ struct rchan_buf *buf;
struct rchan_percpu_buf_dispatcher disp;
if (!chan || !base_filename)
@@ -686,10 +693,11 @@ int relay_late_setup_files(struct rchan *chan,
if (chan->is_global) {
err = -EINVAL;
- if (!WARN_ON_ONCE(!chan->buf[0])) {
- dentry = relay_create_buf_file(chan, chan->buf[0], 0);
+ buf = *per_cpu_ptr(chan->buf, 0);
+ if (!WARN_ON_ONCE(!buf)) {
+ dentry = relay_create_buf_file(chan, buf, 0);
if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
- relay_set_buf_dentry(chan->buf[0], dentry);
+ relay_set_buf_dentry(buf, dentry);
err = 0;
}
}
@@ -704,13 +712,14 @@ int relay_late_setup_files(struct rchan *chan,
* on all currently online CPUs.
*/
for_each_online_cpu(i) {
- if (unlikely(!chan->buf[i])) {
+ buf = *per_cpu_ptr(chan->buf, i);
+ if (unlikely(!buf)) {
WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
err = -EINVAL;
break;
}
- dentry = relay_create_buf_file(chan, chan->buf[i], i);
+ dentry = relay_create_buf_file(chan, buf, i);
if (unlikely(!dentry)) {
err = -EINVAL;
break;
@@ -718,10 +727,10 @@ int relay_late_setup_files(struct rchan *chan,
if (curr_cpu == i) {
local_irq_save(flags);
- relay_set_buf_dentry(chan->buf[i], dentry);
+ relay_set_buf_dentry(buf, dentry);
local_irq_restore(flags);
} else {
- disp.buf = chan->buf[i];
+ disp.buf = buf;
disp.dentry = dentry;
smp_mb();
/* relay_channels_mutex must be held, so wait. */
@@ -824,11 +833,10 @@ void relay_subbufs_consumed(struct rchan *chan,
if (!chan)
return;
- if (cpu >= NR_CPUS || !chan->buf[cpu] ||
- subbufs_consumed > chan->n_subbufs)
+ buf = *per_cpu_ptr(chan->buf, cpu);
+ if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
return;
- buf = chan->buf[cpu];
if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
buf->subbufs_consumed = buf->subbufs_produced;
else
@@ -844,18 +852,19 @@ EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
*/
void relay_close(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
mutex_lock(&relay_channels_mutex);
- if (chan->is_global && chan->buf[0])
- relay_close_buf(chan->buf[0]);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
+ relay_close_buf(buf);
else
for_each_possible_cpu(i)
- if (chan->buf[i])
- relay_close_buf(chan->buf[i]);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_close_buf(buf);
if (chan->last_toobig)
printk(KERN_WARNING "relay: one or more items not logged "
@@ -876,20 +885,21 @@ EXPORT_SYMBOL_GPL(relay_close);
*/
void relay_flush(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
- if (chan->is_global && chan->buf[0]) {
- relay_switch_subbuf(chan->buf[0], 0);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
+ relay_switch_subbuf(buf, 0);
return;
}
mutex_lock(&relay_channels_mutex);
for_each_possible_cpu(i)
- if (chan->buf[i])
- relay_switch_subbuf(chan->buf[i], 0);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_switch_subbuf(buf, 0);
mutex_unlock(&relay_channels_mutex);
}
EXPORT_SYMBOL_GPL(relay_flush);
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