linux-kernel - Re: [PATCH] mm/damon/sysfs: change few functions execute order

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Date:   Fri, 9 Sep 2022 15:44:34 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     SeongJae Park <sj@...nel.org>
Cc:     Xin Hao <xhao@...ux.alibaba.com>, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/damon/sysfs: change few functions execute order

On Thu,  8 Sep 2022 22:16:53 +0000 SeongJae Park <sj@...nel.org> wrote:

> Reviewed-by: SeongJae Park <sj@...nel.org>

Cool.  I rewrote the changelog significantly:

From: Xin Hao <xhao@...ux.alibaba.com>
Subject: mm/damon/sysfs: change few functions execute order
Date: Thu, 8 Sep 2022 16:19:32 +0800

There's no need to run container_of() as early as we do.

The compiler figures this out, but the resulting code is more readable.

Link: https://lkml.kernel.org/r/20220908081932.77370-1-xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
Reviewed-by: SeongJae Park <sj@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 mm/damon/sysfs.c |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

--- a/mm/damon/sysfs.c~mm-damon-sysfs-change-few-functions-execute-order
+++ a/mm/damon/sysfs.c
@@ -1031,8 +1031,7 @@ static ssize_t nr_schemes_show(struct ko
 static ssize_t nr_schemes_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
-	struct damon_sysfs_schemes *schemes = container_of(kobj,
-			struct damon_sysfs_schemes, kobj);
+	struct damon_sysfs_schemes *schemes;
 	int nr, err = kstrtoint(buf, 0, &nr);
 
 	if (err)
@@ -1040,6 +1039,8 @@ static ssize_t nr_schemes_store(struct k
 	if (nr < 0)
 		return -EINVAL;
 
+	schemes = container_of(kobj, struct damon_sysfs_schemes, kobj);
+
 	if (!mutex_trylock(&damon_sysfs_lock))
 		return -EBUSY;
 	err = damon_sysfs_schemes_add_dirs(schemes, nr);
@@ -1237,8 +1238,7 @@ static ssize_t nr_regions_show(struct ko
 static ssize_t nr_regions_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
-	struct damon_sysfs_regions *regions = container_of(kobj,
-			struct damon_sysfs_regions, kobj);
+	struct damon_sysfs_regions *regions;
 	int nr, err = kstrtoint(buf, 0, &nr);
 
 	if (err)
@@ -1246,6 +1246,8 @@ static ssize_t nr_regions_store(struct k
 	if (nr < 0)
 		return -EINVAL;
 
+	regions = container_of(kobj, struct damon_sysfs_regions, kobj);
+
 	if (!mutex_trylock(&damon_sysfs_lock))
 		return -EBUSY;
 	err = damon_sysfs_regions_add_dirs(regions, nr);
@@ -1440,8 +1442,7 @@ static ssize_t nr_targets_show(struct ko
 static ssize_t nr_targets_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
-	struct damon_sysfs_targets *targets = container_of(kobj,
-			struct damon_sysfs_targets, kobj);
+	struct damon_sysfs_targets *targets;
 	int nr, err = kstrtoint(buf, 0, &nr);
 
 	if (err)
@@ -1449,6 +1450,8 @@ static ssize_t nr_targets_store(struct k
 	if (nr < 0)
 		return -EINVAL;
 
+	targets = container_of(kobj, struct damon_sysfs_targets, kobj);
+
 	if (!mutex_trylock(&damon_sysfs_lock))
 		return -EBUSY;
 	err = damon_sysfs_targets_add_dirs(targets, nr);
@@ -1962,8 +1965,7 @@ static ssize_t nr_contexts_show(struct k
 static ssize_t nr_contexts_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
-	struct damon_sysfs_contexts *contexts = container_of(kobj,
-			struct damon_sysfs_contexts, kobj);
+	struct damon_sysfs_contexts *contexts;
 	int nr, err;
 
 	err = kstrtoint(buf, 0, &nr);
@@ -1973,6 +1975,7 @@ static ssize_t nr_contexts_store(struct
 	if (nr < 0 || 1 < nr)
 		return -EINVAL;
 
+	contexts = container_of(kobj, struct damon_sysfs_contexts, kobj);
 	if (!mutex_trylock(&damon_sysfs_lock))
 		return -EBUSY;
 	err = damon_sysfs_contexts_add_dirs(contexts, nr);
@@ -2737,8 +2740,7 @@ static ssize_t nr_kdamonds_show(struct k
 static ssize_t nr_kdamonds_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
-	struct damon_sysfs_kdamonds *kdamonds = container_of(kobj,
-			struct damon_sysfs_kdamonds, kobj);
+	struct damon_sysfs_kdamonds *kdamonds;
 	int nr, err;
 
 	err = kstrtoint(buf, 0, &nr);
@@ -2747,6 +2749,8 @@ static ssize_t nr_kdamonds_store(struct
 	if (nr < 0)
 		return -EINVAL;
 
+	kdamonds = container_of(kobj, struct damon_sysfs_kdamonds, kobj);
+
 	if (!mutex_trylock(&damon_sysfs_lock))
 		return -EBUSY;
 	err = damon_sysfs_kdamonds_add_dirs(kdamonds, nr);
_