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[PATCH 3/3] tmpfs: Initialize sysfs during tmpfs init

André Almeida posted 3 patches 3 weeks, 2 days ago
There is a newer version of this series
[PATCH 3/3] tmpfs: Initialize sysfs during tmpfs init
Posted by André Almeida 3 weeks, 2 days ago 
Instead of using fs_initcall(), initialize sysfs with the rest of the
filesystem. This is the right way to do it because otherwise any error
during tmpfs_sysfs_init() would get silently ignored. It's also useful
if tmpfs' sysfs ever need to display runtime information.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
 mm/shmem.c | 130 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 68 insertions(+), 62 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 6038e1d11987..8ff2f619f531 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5126,6 +5126,66 @@ static struct file_system_type shmem_fs_type = {
 	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP | FS_MGTIME,
 };
 
+#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)
+
+#define __INIT_KOBJ_ATTR(_name, _mode, _show, _store)			\
+{									\
+	.attr	= { .name = __stringify(_name), .mode = _mode },	\
+	.show	= _show,						\
+	.store	= _store,						\
+}
+
+#define TMPFS_ATTR_W(_name, _store)				\
+	static struct kobj_attribute tmpfs_attr_##_name =	\
+			__INIT_KOBJ_ATTR(_name, 0200, NULL, _store)
+
+#define TMPFS_ATTR_RW(_name, _show, _store)			\
+	static struct kobj_attribute tmpfs_attr_##_name =	\
+			__INIT_KOBJ_ATTR(_name, 0644, _show, _store)
+
+#define TMPFS_ATTR_RO(_name, _show)				\
+	static struct kobj_attribute tmpfs_attr_##_name =	\
+			__INIT_KOBJ_ATTR(_name, 0444, _show, NULL)
+
+#if IS_ENABLED(CONFIG_UNICODE)
+static ssize_t casefold_show(struct kobject *kobj, struct kobj_attribute *a,
+			char *buf)
+{
+		return sysfs_emit(buf, "supported\n");
+}
+TMPFS_ATTR_RO(casefold, casefold_show);
+#endif
+
+static struct attribute *tmpfs_attributes[] = {
+#if IS_ENABLED(CONFIG_UNICODE)
+	&tmpfs_attr_casefold.attr,
+#endif
+	NULL
+};
+
+static const struct attribute_group tmpfs_attribute_group = {
+	.attrs = tmpfs_attributes,
+	.name = "features"
+};
+
+static struct kobject *tmpfs_kobj;
+
+static int __init tmpfs_sysfs_init(void)
+{
+	int ret;
+
+	tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj);
+	if (!tmpfs_kobj)
+		return -ENOMEM;
+
+	ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group);
+	if (ret)
+		kobject_put(tmpfs_kobj);
+
+	return ret;
+}
+#endif /* CONFIG_SYSFS && CONFIG_TMPFS */
+
 void __init shmem_init(void)
 {
 	int error;
@@ -5149,6 +5209,14 @@ void __init shmem_init(void)
 		goto out1;
 	}
 
+#ifdef CONFIG_SYSFS
+	error = tmpfs_sysfs_init();
+	if (error) {
+		pr_err("Could not init tmpfs sysfs\n");
+		goto out1;
+	}
+#endif
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
@@ -5546,65 +5614,3 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 	return page;
 }
 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
-
-#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)
-
-#define __INIT_KOBJ_ATTR(_name, _mode, _show, _store)			\
-{									\
-	.attr	= { .name = __stringify(_name), .mode = _mode },	\
-	.show	= _show,						\
-	.store	= _store,						\
-}
-
-#define TMPFS_ATTR_W(_name, _store)				\
-	static struct kobj_attribute tmpfs_attr_##_name =	\
-			__INIT_KOBJ_ATTR(_name, 0200, NULL, _store)
-
-#define TMPFS_ATTR_RW(_name, _show, _store)			\
-	static struct kobj_attribute tmpfs_attr_##_name =	\
-			__INIT_KOBJ_ATTR(_name, 0644, _show, _store)
-
-#define TMPFS_ATTR_RO(_name, _show)				\
-	static struct kobj_attribute tmpfs_attr_##_name =	\
-			__INIT_KOBJ_ATTR(_name, 0444, _show, NULL)
-
-#if IS_ENABLED(CONFIG_UNICODE)
-static ssize_t casefold_show(struct kobject *kobj, struct kobj_attribute *a,
-			char *buf)
-{
-		return sysfs_emit(buf, "supported\n");
-}
-TMPFS_ATTR_RO(casefold, casefold_show);
-#endif
-
-static struct attribute *tmpfs_attributes[] = {
-#if IS_ENABLED(CONFIG_UNICODE)
-	&tmpfs_attr_casefold.attr,
-#endif
-	NULL
-};
-
-static const struct attribute_group tmpfs_attribute_group = {
-	.attrs = tmpfs_attributes,
-	.name = "features"
-};
-
-static struct kobject *tmpfs_kobj;
-
-static int __init tmpfs_sysfs_init(void)
-{
-	int ret;
-
-	tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj);
-	if (!tmpfs_kobj)
-		return -ENOMEM;
-
-	ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group);
-	if (ret)
-		kobject_put(tmpfs_kobj);
-
-	return ret;
-}
-
-fs_initcall(tmpfs_sysfs_init);
-#endif /* CONFIG_SYSFS && CONFIG_TMPFS */
-- 
2.47.0
Re: [PATCH 3/3] tmpfs: Initialize sysfs during tmpfs init
Posted by Nathan Chancellor 3 weeks, 2 days ago 
Hi André,

On Thu, Oct 31, 2024 at 10:37:41PM -0300, André Almeida wrote:
> Instead of using fs_initcall(), initialize sysfs with the rest of the
> filesystem. This is the right way to do it because otherwise any error
> during tmpfs_sysfs_init() would get silently ignored. It's also useful
> if tmpfs' sysfs ever need to display runtime information.
> 
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
>  mm/shmem.c | 130 ++++++++++++++++++++++++++++-------------------------
>  1 file changed, 68 insertions(+), 62 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 6038e1d11987..8ff2f619f531 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -5126,6 +5126,66 @@ static struct file_system_type shmem_fs_type = {
>  	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP | FS_MGTIME,
>  };
>  
> +#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)

This condition...

> +static int __init tmpfs_sysfs_init(void)
> +{
> +	int ret;
> +
> +	tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj);
> +	if (!tmpfs_kobj)
> +		return -ENOMEM;
> +
> +	ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group);
> +	if (ret)
> +		kobject_put(tmpfs_kobj);
> +
> +	return ret;
> +}
> +#endif /* CONFIG_SYSFS && CONFIG_TMPFS */
> +
>  void __init shmem_init(void)
>  {
>  	int error;
> @@ -5149,6 +5209,14 @@ void __init shmem_init(void)
>  		goto out1;
>  	}
>  
> +#ifdef CONFIG_SYSFS

and this condition are not the same, so there will be a compile error if
CONFIG_SHMEM and CONFIG_SYSFS are enabled but CONFIG_TMPFS is not, such
as with ARCH=x86_64 allnoconfig for me:

  mm/shmem.c: In function 'shmem_init':
  mm/shmem.c:5243:17: error: implicit declaration of function 'tmpfs_sysfs_init'; did you mean 'uids_sysfs_init'? [-Wimplicit-function-declaration]
   5243 |         error = tmpfs_sysfs_init();
        |                 ^~~~~~~~~~~~~~~~
        |                 uids_sysfs_init

> +	error = tmpfs_sysfs_init();
> +	if (error) {
> +		pr_err("Could not init tmpfs sysfs\n");
> +		goto out1;
> +	}
> +#endif

Cheers,
Nathan
Re: [PATCH 3/3] tmpfs: Initialize sysfs during tmpfs init
Posted by André Almeida 3 weeks, 2 days ago 
Em 01/11/2024 04:19, Nathan Chancellor escreveu:
> Hi André,
> 
> On Thu, Oct 31, 2024 at 10:37:41PM -0300, André Almeida wrote:
>> Instead of using fs_initcall(), initialize sysfs with the rest of the
>> filesystem. This is the right way to do it because otherwise any error
>> during tmpfs_sysfs_init() would get silently ignored. It's also useful
>> if tmpfs' sysfs ever need to display runtime information.
>>
>> Signed-off-by: André Almeida <andrealmeid@igalia.com>
>> ---
>>   mm/shmem.c | 130 ++++++++++++++++++++++++++++-------------------------
>>   1 file changed, 68 insertions(+), 62 deletions(-)
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 6038e1d11987..8ff2f619f531 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -5126,6 +5126,66 @@ static struct file_system_type shmem_fs_type = {
>>   	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP | FS_MGTIME,
>>   };
>>   
>> +#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)
> 
> This condition...
> 
>> +static int __init tmpfs_sysfs_init(void)
>> +{
>> +	int ret;
>> +
>> +	tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj);
>> +	if (!tmpfs_kobj)
>> +		return -ENOMEM;
>> +
>> +	ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group);
>> +	if (ret)
>> +		kobject_put(tmpfs_kobj);
>> +
>> +	return ret;
>> +}
>> +#endif /* CONFIG_SYSFS && CONFIG_TMPFS */
>> +
>>   void __init shmem_init(void)
>>   {
>>   	int error;
>> @@ -5149,6 +5209,14 @@ void __init shmem_init(void)
>>   		goto out1;
>>   	}
>>   
>> +#ifdef CONFIG_SYSFS
> 
> and this condition are not the same, so there will be a compile error if
> CONFIG_SHMEM and CONFIG_SYSFS are enabled but CONFIG_TMPFS is not, such
> as with ARCH=x86_64 allnoconfig for me:
> 
>    mm/shmem.c: In function 'shmem_init':
>    mm/shmem.c:5243:17: error: implicit declaration of function 'tmpfs_sysfs_init'; did you mean 'uids_sysfs_init'? [-Wimplicit-function-declaration]
>     5243 |         error = tmpfs_sysfs_init();
>          |                 ^~~~~~~~~~~~~~~~
>          |                 uids_sysfs_init
> 

Thanks for the catch! Fixed for v2

>> +	error = tmpfs_sysfs_init();
>> +	if (error) {
>> +		pr_err("Could not init tmpfs sysfs\n");
>> +		goto out1;
>> +	}
>> +#endif
> 
> Cheers,
> Nathan

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