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Date: Mon, 2 May 2016 17:06:00 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To: Minchan Kim <minchan@...nel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH 2/2] zram: user per-cpu compression streams
On (05/02/16 16:25), Sergey Senozhatsky wrote:
[..]
> > Trivial:
> > We could remove max_strm now and change description.
>
> oh, yes.
how about something like this? remove max_comp_streams entirely, but
leave the attr. if we keep zram->max_comp_streams and return its value
(set by user space) from show() handler, we are techically lying;
because the actual number of streams is now num_online_cpus().
===8<===8<===
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH] zram: remove max_comp_streams internals
Remove the internal part of max_comp_streams interface, since we
switched to per-cpu streams. We will keep RW max_comp_streams attr
around, because:
a) we may (silently) switch back to idle compression streams list
and don't want to disturb user space
b) max_comp_streams attr must wait for the next 'lay off cycle';
we give user space 2 years to adjust before we remove/downgrade
the attr, and there are already several attrs scheduled for
removal in 4.11, so it's too late for max_comp_streams.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
drivers/block/zram/zcomp.c | 7 +------
drivers/block/zram/zcomp.h | 2 +-
drivers/block/zram/zram_drv.c | 47 +++++++++++--------------------------------
drivers/block/zram/zram_drv.h | 1 -
4 files changed, 14 insertions(+), 43 deletions(-)
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index d4159e4..d4de9cb 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -95,11 +95,6 @@ bool zcomp_available_algorithm(const char *comp)
return find_backend(comp) != NULL;
}
-bool zcomp_set_max_streams(struct zcomp *comp, int num_strm)
-{
- return true;
-}
-
struct zcomp_strm *zcomp_strm_find(struct zcomp *comp)
{
return *get_cpu_ptr(comp->stream);
@@ -211,7 +206,7 @@ void zcomp_destroy(struct zcomp *comp)
* case of allocation error, or any other error potentially
* returned by functions zcomp_strm_{multi,single}_create.
*/
-struct zcomp *zcomp_create(const char *compress, int max_strm)
+struct zcomp *zcomp_create(const char *compress)
{
struct zcomp *comp;
struct zcomp_backend *backend;
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index aba8c21..ffd88cb 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -45,7 +45,7 @@ struct zcomp {
ssize_t zcomp_available_show(const char *comp, char *buf);
bool zcomp_available_algorithm(const char *comp);
-struct zcomp *zcomp_create(const char *comp, int max_strm);
+struct zcomp *zcomp_create(const char *comp);
void zcomp_destroy(struct zcomp *comp);
struct zcomp_strm *zcomp_strm_find(struct zcomp *comp);
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index cad1751..817e511 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -304,46 +304,25 @@ static ssize_t mem_used_max_store(struct device *dev,
return len;
}
+/*
+ * We switched to per-cpu streams and this attr is not needed anymore.
+ * However, we will keep it around for some time, because:
+ * a) we may revert per-cpu streams in the future
+ * b) it's visible to user space and we need to follow our 2 years
+ * retirement rule; but we already have a number of 'soon to be
+ * altered' attrs, so max_comp_streams need to wait for the next
+ * layoff cycle.
+ */
static ssize_t max_comp_streams_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- int val;
- struct zram *zram = dev_to_zram(dev);
-
- down_read(&zram->init_lock);
- val = zram->max_comp_streams;
- up_read(&zram->init_lock);
-
- return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+ return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
}
static ssize_t max_comp_streams_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
- int num;
- struct zram *zram = dev_to_zram(dev);
- int ret;
-
- ret = kstrtoint(buf, 0, &num);
- if (ret < 0)
- return ret;
- if (num < 1)
- return -EINVAL;
-
- down_write(&zram->init_lock);
- if (init_done(zram)) {
- if (!zcomp_set_max_streams(zram->comp, num)) {
- pr_info("Cannot change max compression streams\n");
- ret = -EINVAL;
- goto out;
- }
- }
-
- zram->max_comp_streams = num;
- ret = len;
-out:
- up_write(&zram->init_lock);
- return ret;
+ return len;
}
static ssize_t comp_algorithm_show(struct device *dev,
@@ -1035,7 +1014,6 @@ static void zram_reset_device(struct zram *zram)
/* Reset stats */
memset(&zram->stats, 0, sizeof(zram->stats));
zram->disksize = 0;
- zram->max_comp_streams = 1;
set_capacity(zram->disk, 0);
part_stat_set_all(&zram->disk->part0, 0);
@@ -1064,7 +1042,7 @@ static ssize_t disksize_store(struct device *dev,
if (!meta)
return -ENOMEM;
- comp = zcomp_create(zram->compressor, zram->max_comp_streams);
+ comp = zcomp_create(zram->compressor);
if (IS_ERR(comp)) {
pr_err("Cannot initialise %s compressing backend\n",
zram->compressor);
@@ -1299,7 +1277,6 @@ static int zram_add(void)
}
strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
zram->meta = NULL;
- zram->max_comp_streams = 1;
pr_info("Added device: %s\n", zram->disk->disk_name);
return device_id;
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 8e92339..06b1636 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -102,7 +102,6 @@ struct zram {
* the number of pages zram can consume for storing compressed data
*/
unsigned long limit_pages;
- int max_comp_streams;
struct zram_stats stats;
atomic_t refcount; /* refcount for zram_meta */
--
2.8.2
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