* + zram-drop-wb_limit_lock.patch added to mm-unstable branch
@ 2025-11-18 18:12 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2025-11-18 18:12 UTC (permalink / raw)
To: mm-commits, ywen.chen, richardycc, minchan, bgeffon, senozhatsky,
akpm
The patch titled
Subject: zram: drop wb_limit_lock
has been added to the -mm mm-unstable branch. Its filename is
zram-drop-wb_limit_lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-drop-wb_limit_lock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: drop wb_limit_lock
Date: Tue, 18 Nov 2025 16:29:58 +0900
We don't need wb_limit_lock. Writeback limit setters take an exclusive
write zram init_lock, while wb_limit modifications happen only from a
single task and under zram read init_lock. No concurrent wb_limit
modifications are possible (we permit only one post-processing task at a
time). Add lockdep assertions to wb_limit mutators.
While at it, fixup coding styles.
Link: https://lkml.kernel.org/r/20251118073000.1928107-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Yuwen Chen <ywen.chen@foxmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
drivers/block/zram/zram_drv.c | 22 +++++-----------------
drivers/block/zram/zram_drv.h | 1 -
2 files changed, 5 insertions(+), 18 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-drop-wb_limit_lock
+++ a/drivers/block/zram/zram_drv.c
@@ -530,9 +530,7 @@ static ssize_t writeback_limit_enable_st
return ret;
down_write(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
zram->wb_limit_enable = val;
- spin_unlock(&zram->wb_limit_lock);
up_write(&zram->init_lock);
ret = len;
@@ -547,9 +545,7 @@ static ssize_t writeback_limit_enable_sh
struct zram *zram = dev_to_zram(dev);
down_read(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
val = zram->wb_limit_enable;
- spin_unlock(&zram->wb_limit_lock);
up_read(&zram->init_lock);
return sysfs_emit(buf, "%d\n", val);
@@ -567,9 +563,7 @@ static ssize_t writeback_limit_store(str
return ret;
down_write(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
zram->bd_wb_limit = val;
- spin_unlock(&zram->wb_limit_lock);
up_write(&zram->init_lock);
ret = len;
@@ -577,15 +571,13 @@ static ssize_t writeback_limit_store(str
}
static ssize_t writeback_limit_show(struct device *dev,
- struct device_attribute *attr, char *buf)
+ struct device_attribute *attr, char *buf)
{
u64 val;
struct zram *zram = dev_to_zram(dev);
down_read(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
val = zram->bd_wb_limit;
- spin_unlock(&zram->wb_limit_lock);
up_read(&zram->init_lock);
return sysfs_emit(buf, "%llu\n", val);
@@ -864,18 +856,18 @@ release_wb_ctl:
static void zram_account_writeback_rollback(struct zram *zram)
{
- spin_lock(&zram->wb_limit_lock);
+ lockdep_assert_held_read(&zram->init_lock);
+
if (zram->wb_limit_enable)
zram->bd_wb_limit += 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
}
static void zram_account_writeback_submit(struct zram *zram)
{
- spin_lock(&zram->wb_limit_lock);
+ lockdep_assert_held_read(&zram->init_lock);
+
if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
}
static int zram_writeback_complete(struct zram *zram, struct zram_wb_req *req)
@@ -992,13 +984,10 @@ static int zram_writeback_slots(struct z
blk_start_plug(&io_plug);
while ((pps = select_pp_slot(ctl))) {
- spin_lock(&zram->wb_limit_lock);
if (zram->wb_limit_enable && !zram->bd_wb_limit) {
- spin_unlock(&zram->wb_limit_lock);
ret = -EIO;
break;
}
- spin_unlock(&zram->wb_limit_lock);
while (!req) {
req = select_idle_req(wb_ctl);
@@ -2947,7 +2936,6 @@ static int zram_add(void)
init_rwsem(&zram->init_lock);
#ifdef CONFIG_ZRAM_WRITEBACK
zram->wb_batch_size = 32;
- spin_lock_init(&zram->wb_limit_lock);
#endif
/* gendisk structure */
--- a/drivers/block/zram/zram_drv.h~zram-drop-wb_limit_lock
+++ a/drivers/block/zram/zram_drv.h
@@ -127,7 +127,6 @@ struct zram {
bool claim; /* Protected by disk->open_mutex */
#ifdef CONFIG_ZRAM_WRITEBACK
struct file *backing_dev;
- spinlock_t wb_limit_lock;
bool wb_limit_enable;
u32 wb_batch_size;
u64 bd_wb_limit;
_
Patches currently in -mm which might be from senozhatsky@chromium.org are
zram-add-writeback-batch-size-device-attr.patch
zram-take-write-lock-in-wb-limit-store-handlers.patch
zram-drop-wb_limit_lock.patch
zram-rework-bdev-block-allocation.patch
zram-read-slot-block-idx-under-slot-lock.patch
^ permalink raw reply [flat|nested] 2+ messages in thread* + zram-drop-wb_limit_lock.patch added to mm-unstable branch
@ 2025-11-17 18:44 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2025-11-17 18:44 UTC (permalink / raw)
To: mm-commits, ywen.chen, richardycc, minchan, bgeffon, senozhatsky,
akpm
The patch titled
Subject: zram: drop wb_limit_lock
has been added to the -mm mm-unstable branch. Its filename is
zram-drop-wb_limit_lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-drop-wb_limit_lock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: drop wb_limit_lock
Date: Sat, 15 Nov 2025 11:34:47 +0900
We don't need wb_limit_lock. Writeback limit setters take an exclusive
write zram init_lock, while wb_limit modifications happen only from a
single task and under zram read init_lock. No concurrent wb_limit
modifications are possible (we permit only one post-processing task at a
time). Add lockdep assertions to wb_limit mutators.
While at it, fixup coding styles.
Link: https://lkml.kernel.org/r/20251115023447.495417-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Yuwen Chen <ywen.chen@foxmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
drivers/block/zram/zram_drv.c | 22 +++++-----------------
drivers/block/zram/zram_drv.h | 1 -
2 files changed, 5 insertions(+), 18 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-drop-wb_limit_lock
+++ a/drivers/block/zram/zram_drv.c
@@ -530,9 +530,7 @@ static ssize_t writeback_limit_enable_st
return ret;
down_write(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
zram->wb_limit_enable = val;
- spin_unlock(&zram->wb_limit_lock);
up_write(&zram->init_lock);
ret = len;
@@ -547,9 +545,7 @@ static ssize_t writeback_limit_enable_sh
struct zram *zram = dev_to_zram(dev);
down_read(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
val = zram->wb_limit_enable;
- spin_unlock(&zram->wb_limit_lock);
up_read(&zram->init_lock);
return sysfs_emit(buf, "%d\n", val);
@@ -567,9 +563,7 @@ static ssize_t writeback_limit_store(str
return ret;
down_write(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
zram->bd_wb_limit = val;
- spin_unlock(&zram->wb_limit_lock);
up_write(&zram->init_lock);
ret = len;
@@ -577,15 +571,13 @@ static ssize_t writeback_limit_store(str
}
static ssize_t writeback_limit_show(struct device *dev,
- struct device_attribute *attr, char *buf)
+ struct device_attribute *attr, char *buf)
{
u64 val;
struct zram *zram = dev_to_zram(dev);
down_read(&zram->init_lock);
- spin_lock(&zram->wb_limit_lock);
val = zram->bd_wb_limit;
- spin_unlock(&zram->wb_limit_lock);
up_read(&zram->init_lock);
return sysfs_emit(buf, "%llu\n", val);
@@ -864,18 +856,18 @@ release_wb_ctl:
static void zram_account_writeback_rollback(struct zram *zram)
{
- spin_lock(&zram->wb_limit_lock);
+ lockdep_assert_held_read(&zram->init_lock);
+
if (zram->wb_limit_enable)
zram->bd_wb_limit += 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
}
static void zram_account_writeback_submit(struct zram *zram)
{
- spin_lock(&zram->wb_limit_lock);
+ lockdep_assert_held_read(&zram->init_lock);
+
if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
}
static int zram_writeback_complete(struct zram *zram, struct zram_wb_req *req)
@@ -990,13 +982,10 @@ static int zram_writeback_slots(struct z
blk_start_plug(&io_plug);
while ((pps = select_pp_slot(ctl))) {
- spin_lock(&zram->wb_limit_lock);
if (zram->wb_limit_enable && !zram->bd_wb_limit) {
- spin_unlock(&zram->wb_limit_lock);
ret = -EIO;
break;
}
- spin_unlock(&zram->wb_limit_lock);
while (!req) {
req = select_idle_req(wb_ctl);
@@ -2942,7 +2931,6 @@ static int zram_add(void)
init_rwsem(&zram->init_lock);
#ifdef CONFIG_ZRAM_WRITEBACK
zram->wb_batch_size = 32;
- spin_lock_init(&zram->wb_limit_lock);
#endif
/* gendisk structure */
--- a/drivers/block/zram/zram_drv.h~zram-drop-wb_limit_lock
+++ a/drivers/block/zram/zram_drv.h
@@ -127,7 +127,6 @@ struct zram {
bool claim; /* Protected by disk->open_mutex */
#ifdef CONFIG_ZRAM_WRITEBACK
struct file *backing_dev;
- spinlock_t wb_limit_lock;
bool wb_limit_enable;
u32 wb_batch_size;
u64 bd_wb_limit;
_
Patches currently in -mm which might be from senozhatsky@chromium.org are
zram-add-writeback-batch-size-device-attr.patch
zram-take-write-lock-in-wb-limit-store-handlers.patch
zram-drop-wb_limit_lock.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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