[PATCH] f2fs: add symbolic link to kobject in sysfs

[PATCH] f2fs: add symbolic link to kobject in sysfs

[Daeho Jeong]

From: Daeho Jeong <daehojeong@google.com>

Added a symbolic link to directory of sysfs. It will
create a symbolic link such as "mount_0" and "mount_1" to
each f2fs mount in the order of mounting filesystem. It will
provide easy access to sysfs node even if not knowing the
specific device node name like sda19 and dm-3.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
 fs/f2fs/f2fs.h  |  4 ++++
 fs/f2fs/sysfs.c | 31 +++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4b28fd42fdbc..7d6c5f8ce16b 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1419,6 +1419,8 @@ struct decompress_io_ctx {
 #define MAX_COMPRESS_LOG_SIZE		8
 #define MAX_COMPRESS_WINDOW_SIZE	((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
 
+#define MOUNT_NAME_SIZE			20
+
 struct f2fs_sb_info {
 	struct super_block *sb;			/* pointer to VFS super block */
 	struct proc_dir_entry *s_proc;		/* proc entry */
@@ -1599,6 +1601,8 @@ struct f2fs_sb_info {
 	/* For sysfs suppport */
 	struct kobject s_kobj;
 	struct completion s_kobj_unregister;
+	int s_mount_id;
+	char s_mount_name[MOUNT_NAME_SIZE];
 
 	/* For shrinker support */
 	struct list_head s_list;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index ab40e1f89f23..64bbe0b3b830 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -18,6 +18,7 @@
 #include <trace/events/f2fs.h>
 
 static struct proc_dir_entry *f2fs_proc_root;
+static struct ida f2fs_mount_ida;
 
 /* Sysfs support for f2fs */
 enum {
@@ -906,6 +907,9 @@ int __init f2fs_init_sysfs(void)
 	} else {
 		f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
 	}
+
+	ida_init(&f2fs_mount_ida);
+
 	return ret;
 }
 
@@ -915,6 +919,7 @@ void f2fs_exit_sysfs(void)
 	kset_unregister(&f2fs_kset);
 	remove_proc_entry("fs/f2fs", NULL);
 	f2fs_proc_root = NULL;
+	ida_destroy(&f2fs_mount_ida);
 }
 
 int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
@@ -926,12 +931,22 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 	init_completion(&sbi->s_kobj_unregister);
 	err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
 				"%s", sb->s_id);
-	if (err) {
-		kobject_put(&sbi->s_kobj);
-		wait_for_completion(&sbi->s_kobj_unregister);
-		return err;
+	if (err)
+		goto err1;
+
+	sbi->s_mount_id = ida_simple_get(&f2fs_mount_ida, 0, 0, GFP_KERNEL);
+	if (sbi->s_mount_id < 0) {
+		err = sbi->s_mount_id;
+		goto err1;
 	}
 
+	snprintf(sbi->s_mount_name, MOUNT_NAME_SIZE, "mount_%d",
+			sbi->s_mount_id);
+	err = sysfs_create_link(&f2fs_kset.kobj, &sbi->s_kobj,
+			sbi->s_mount_name);
+	if (err)
+		goto err2;
+
 	if (f2fs_proc_root)
 		sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
 
@@ -946,6 +961,12 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 				victim_bits_seq_show, sb);
 	}
 	return 0;
+err2:
+	ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
+err1:
+	kobject_put(&sbi->s_kobj);
+	wait_for_completion(&sbi->s_kobj_unregister);
+	return err;
 }
 
 void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
@@ -957,6 +978,8 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
 		remove_proc_entry("victim_bits", sbi->s_proc);
 		remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
 	}
+	sysfs_remove_link(&f2fs_kset.kobj, sbi->s_mount_name);
+	ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
 	kobject_del(&sbi->s_kobj);
 	kobject_put(&sbi->s_kobj);
 }
-- 
2.27.0.212.ge8ba1cc988-goog

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Chao Yu]

Hi Daeho,

On 2020/6/30 8:56, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> Added a symbolic link to directory of sysfs. It will
> create a symbolic link such as "mount_0" and "mount_1" to
> each f2fs mount in the order of mounting filesystem. It will
> provide easy access to sysfs node even if not knowing the
> specific device node name like sda19 and dm-3.

Just out of curiosity, if we mount/umount as below:

mount /dev/zram0 /mnt/f2fs0
mount /dev/zram1 /mnt/f2fs1
umount /mnt/f2fs0
mount /dev/zram0 /mnt/f2fs0

Shouldn't sysfs structure be:
mount_2 -> zram0
mount_1 -> zram1
zram0
zram1

Then we can know zram0 is mounted after zram1?

However the result shows:
mount_0 -> zram0
mount_1 -> zram1
zram0
zram1

Thanks,

> 
> Signed-off-by: Daeho Jeong <daehojeong@google.com>
> ---
>  fs/f2fs/f2fs.h  |  4 ++++
>  fs/f2fs/sysfs.c | 31 +++++++++++++++++++++++++++----
>  2 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 4b28fd42fdbc..7d6c5f8ce16b 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1419,6 +1419,8 @@ struct decompress_io_ctx {
>  #define MAX_COMPRESS_LOG_SIZE		8
>  #define MAX_COMPRESS_WINDOW_SIZE	((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
>  
> +#define MOUNT_NAME_SIZE			20
> +
>  struct f2fs_sb_info {
>  	struct super_block *sb;			/* pointer to VFS super block */
>  	struct proc_dir_entry *s_proc;		/* proc entry */
> @@ -1599,6 +1601,8 @@ struct f2fs_sb_info {
>  	/* For sysfs suppport */
>  	struct kobject s_kobj;
>  	struct completion s_kobj_unregister;
> +	int s_mount_id;
> +	char s_mount_name[MOUNT_NAME_SIZE];
>  
>  	/* For shrinker support */
>  	struct list_head s_list;
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index ab40e1f89f23..64bbe0b3b830 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -18,6 +18,7 @@
>  #include <trace/events/f2fs.h>
>  
>  static struct proc_dir_entry *f2fs_proc_root;
> +static struct ida f2fs_mount_ida;
>  
>  /* Sysfs support for f2fs */
>  enum {
> @@ -906,6 +907,9 @@ int __init f2fs_init_sysfs(void)
>  	} else {
>  		f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
>  	}
> +
> +	ida_init(&f2fs_mount_ida);
> +
>  	return ret;
>  }
>  
> @@ -915,6 +919,7 @@ void f2fs_exit_sysfs(void)
>  	kset_unregister(&f2fs_kset);
>  	remove_proc_entry("fs/f2fs", NULL);
>  	f2fs_proc_root = NULL;
> +	ida_destroy(&f2fs_mount_ida);
>  }
>  
>  int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
> @@ -926,12 +931,22 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
>  	init_completion(&sbi->s_kobj_unregister);
>  	err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
>  				"%s", sb->s_id);
> -	if (err) {
> -		kobject_put(&sbi->s_kobj);
> -		wait_for_completion(&sbi->s_kobj_unregister);
> -		return err;
> +	if (err)
> +		goto err1;
> +
> +	sbi->s_mount_id = ida_simple_get(&f2fs_mount_ida, 0, 0, GFP_KERNEL);
> +	if (sbi->s_mount_id < 0) {
> +		err = sbi->s_mount_id;
> +		goto err1;
>  	}
>  
> +	snprintf(sbi->s_mount_name, MOUNT_NAME_SIZE, "mount_%d",
> +			sbi->s_mount_id);
> +	err = sysfs_create_link(&f2fs_kset.kobj, &sbi->s_kobj,
> +			sbi->s_mount_name);
> +	if (err)
> +		goto err2;
> +
>  	if (f2fs_proc_root)
>  		sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
>  
> @@ -946,6 +961,12 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
>  				victim_bits_seq_show, sb);
>  	}
>  	return 0;
> +err2:
> +	ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
> +err1:
> +	kobject_put(&sbi->s_kobj);
> +	wait_for_completion(&sbi->s_kobj_unregister);
> +	return err;
>  }
>  
>  void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
> @@ -957,6 +978,8 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
>  		remove_proc_entry("victim_bits", sbi->s_proc);
>  		remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
>  	}
> +	sysfs_remove_link(&f2fs_kset.kobj, sbi->s_mount_name);
> +	ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
>  	kobject_del(&sbi->s_kobj);
>  	kobject_put(&sbi->s_kobj);
>  }
> 

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Daeho Jeong]

Actually, I want to keep the mount number remaining to the same
number, even if it's re-mounted.
Or we need to keep track of the number being increased whenever it's
remounted. :(

2020년 7월 1일 (수) 오후 3:36, Chao Yu <yuchao0@huawei.com>님이 작성:
>
> Hi Daeho,
>
> On 2020/6/30 8:56, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@google.com>
> >
> > Added a symbolic link to directory of sysfs. It will
> > create a symbolic link such as "mount_0" and "mount_1" to
> > each f2fs mount in the order of mounting filesystem. It will
> > provide easy access to sysfs node even if not knowing the
> > specific device node name like sda19 and dm-3.
>
> Just out of curiosity, if we mount/umount as below:
>
> mount /dev/zram0 /mnt/f2fs0
> mount /dev/zram1 /mnt/f2fs1
> umount /mnt/f2fs0
> mount /dev/zram0 /mnt/f2fs0
>
> Shouldn't sysfs structure be:
> mount_2 -> zram0
> mount_1 -> zram1
> zram0
> zram1
>
> Then we can know zram0 is mounted after zram1?
>
> However the result shows:
> mount_0 -> zram0
> mount_1 -> zram1
> zram0
> zram1
>
> Thanks,
>
> >
> > Signed-off-by: Daeho Jeong <daehojeong@google.com>
> > ---
> >  fs/f2fs/f2fs.h  |  4 ++++
> >  fs/f2fs/sysfs.c | 31 +++++++++++++++++++++++++++----
> >  2 files changed, 31 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 4b28fd42fdbc..7d6c5f8ce16b 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1419,6 +1419,8 @@ struct decompress_io_ctx {
> >  #define MAX_COMPRESS_LOG_SIZE                8
> >  #define MAX_COMPRESS_WINDOW_SIZE     ((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
> >
> > +#define MOUNT_NAME_SIZE                      20
> > +
> >  struct f2fs_sb_info {
> >       struct super_block *sb;                 /* pointer to VFS super block */
> >       struct proc_dir_entry *s_proc;          /* proc entry */
> > @@ -1599,6 +1601,8 @@ struct f2fs_sb_info {
> >       /* For sysfs suppport */
> >       struct kobject s_kobj;
> >       struct completion s_kobj_unregister;
> > +     int s_mount_id;
> > +     char s_mount_name[MOUNT_NAME_SIZE];
> >
> >       /* For shrinker support */
> >       struct list_head s_list;
> > diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> > index ab40e1f89f23..64bbe0b3b830 100644
> > --- a/fs/f2fs/sysfs.c
> > +++ b/fs/f2fs/sysfs.c
> > @@ -18,6 +18,7 @@
> >  #include <trace/events/f2fs.h>
> >
> >  static struct proc_dir_entry *f2fs_proc_root;
> > +static struct ida f2fs_mount_ida;
> >
> >  /* Sysfs support for f2fs */
> >  enum {
> > @@ -906,6 +907,9 @@ int __init f2fs_init_sysfs(void)
> >       } else {
> >               f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
> >       }
> > +
> > +     ida_init(&f2fs_mount_ida);
> > +
> >       return ret;
> >  }
> >
> > @@ -915,6 +919,7 @@ void f2fs_exit_sysfs(void)
> >       kset_unregister(&f2fs_kset);
> >       remove_proc_entry("fs/f2fs", NULL);
> >       f2fs_proc_root = NULL;
> > +     ida_destroy(&f2fs_mount_ida);
> >  }
> >
> >  int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
> > @@ -926,12 +931,22 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
> >       init_completion(&sbi->s_kobj_unregister);
> >       err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
> >                               "%s", sb->s_id);
> > -     if (err) {
> > -             kobject_put(&sbi->s_kobj);
> > -             wait_for_completion(&sbi->s_kobj_unregister);
> > -             return err;
> > +     if (err)
> > +             goto err1;
> > +
> > +     sbi->s_mount_id = ida_simple_get(&f2fs_mount_ida, 0, 0, GFP_KERNEL);
> > +     if (sbi->s_mount_id < 0) {
> > +             err = sbi->s_mount_id;
> > +             goto err1;
> >       }
> >
> > +     snprintf(sbi->s_mount_name, MOUNT_NAME_SIZE, "mount_%d",
> > +                     sbi->s_mount_id);
> > +     err = sysfs_create_link(&f2fs_kset.kobj, &sbi->s_kobj,
> > +                     sbi->s_mount_name);
> > +     if (err)
> > +             goto err2;
> > +
> >       if (f2fs_proc_root)
> >               sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
> >
> > @@ -946,6 +961,12 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
> >                               victim_bits_seq_show, sb);
> >       }
> >       return 0;
> > +err2:
> > +     ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
> > +err1:
> > +     kobject_put(&sbi->s_kobj);
> > +     wait_for_completion(&sbi->s_kobj_unregister);
> > +     return err;
> >  }
> >
> >  void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
> > @@ -957,6 +978,8 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
> >               remove_proc_entry("victim_bits", sbi->s_proc);
> >               remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
> >       }
> > +     sysfs_remove_link(&f2fs_kset.kobj, sbi->s_mount_name);
> > +     ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
> >       kobject_del(&sbi->s_kobj);
> >       kobject_put(&sbi->s_kobj);
> >  }
> >

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Chao Yu]

On 2020/7/1 15:04, Daeho Jeong wrote:
> Actually, I want to keep the mount number remaining to the same
> number, even if it's re-mounted.

Then once there is f2fs umounter, the order will be incorrect...

> Or we need to keep track of the number being increased whenever it's
> remounted. :(

IMO, it needs to always keep the number being increased.

Thanks,

> 
> 2020년 7월 1일 (수) 오후 3:36, Chao Yu <yuchao0@huawei.com>님이 작성:
>>
>> Hi Daeho,
>>
>> On 2020/6/30 8:56, Daeho Jeong wrote:
>>> From: Daeho Jeong <daehojeong@google.com>
>>>
>>> Added a symbolic link to directory of sysfs. It will
>>> create a symbolic link such as "mount_0" and "mount_1" to
>>> each f2fs mount in the order of mounting filesystem. It will
>>> provide easy access to sysfs node even if not knowing the
>>> specific device node name like sda19 and dm-3.
>>
>> Just out of curiosity, if we mount/umount as below:
>>
>> mount /dev/zram0 /mnt/f2fs0
>> mount /dev/zram1 /mnt/f2fs1
>> umount /mnt/f2fs0
>> mount /dev/zram0 /mnt/f2fs0
>>
>> Shouldn't sysfs structure be:
>> mount_2 -> zram0
>> mount_1 -> zram1
>> zram0
>> zram1
>>
>> Then we can know zram0 is mounted after zram1?
>>
>> However the result shows:
>> mount_0 -> zram0
>> mount_1 -> zram1
>> zram0
>> zram1
>>
>> Thanks,
>>
>>>
>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>> ---
>>>  fs/f2fs/f2fs.h  |  4 ++++
>>>  fs/f2fs/sysfs.c | 31 +++++++++++++++++++++++++++----
>>>  2 files changed, 31 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 4b28fd42fdbc..7d6c5f8ce16b 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -1419,6 +1419,8 @@ struct decompress_io_ctx {
>>>  #define MAX_COMPRESS_LOG_SIZE                8
>>>  #define MAX_COMPRESS_WINDOW_SIZE     ((PAGE_SIZE) << MAX_COMPRESS_LOG_SIZE)
>>>
>>> +#define MOUNT_NAME_SIZE                      20
>>> +
>>>  struct f2fs_sb_info {
>>>       struct super_block *sb;                 /* pointer to VFS super block */
>>>       struct proc_dir_entry *s_proc;          /* proc entry */
>>> @@ -1599,6 +1601,8 @@ struct f2fs_sb_info {
>>>       /* For sysfs suppport */
>>>       struct kobject s_kobj;
>>>       struct completion s_kobj_unregister;
>>> +     int s_mount_id;
>>> +     char s_mount_name[MOUNT_NAME_SIZE];
>>>
>>>       /* For shrinker support */
>>>       struct list_head s_list;
>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>> index ab40e1f89f23..64bbe0b3b830 100644
>>> --- a/fs/f2fs/sysfs.c
>>> +++ b/fs/f2fs/sysfs.c
>>> @@ -18,6 +18,7 @@
>>>  #include <trace/events/f2fs.h>
>>>
>>>  static struct proc_dir_entry *f2fs_proc_root;
>>> +static struct ida f2fs_mount_ida;
>>>
>>>  /* Sysfs support for f2fs */
>>>  enum {
>>> @@ -906,6 +907,9 @@ int __init f2fs_init_sysfs(void)
>>>       } else {
>>>               f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
>>>       }
>>> +
>>> +     ida_init(&f2fs_mount_ida);
>>> +
>>>       return ret;
>>>  }
>>>
>>> @@ -915,6 +919,7 @@ void f2fs_exit_sysfs(void)
>>>       kset_unregister(&f2fs_kset);
>>>       remove_proc_entry("fs/f2fs", NULL);
>>>       f2fs_proc_root = NULL;
>>> +     ida_destroy(&f2fs_mount_ida);
>>>  }
>>>
>>>  int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
>>> @@ -926,12 +931,22 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
>>>       init_completion(&sbi->s_kobj_unregister);
>>>       err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
>>>                               "%s", sb->s_id);
>>> -     if (err) {
>>> -             kobject_put(&sbi->s_kobj);
>>> -             wait_for_completion(&sbi->s_kobj_unregister);
>>> -             return err;
>>> +     if (err)
>>> +             goto err1;
>>> +
>>> +     sbi->s_mount_id = ida_simple_get(&f2fs_mount_ida, 0, 0, GFP_KERNEL);
>>> +     if (sbi->s_mount_id < 0) {
>>> +             err = sbi->s_mount_id;
>>> +             goto err1;
>>>       }
>>>
>>> +     snprintf(sbi->s_mount_name, MOUNT_NAME_SIZE, "mount_%d",
>>> +                     sbi->s_mount_id);
>>> +     err = sysfs_create_link(&f2fs_kset.kobj, &sbi->s_kobj,
>>> +                     sbi->s_mount_name);
>>> +     if (err)
>>> +             goto err2;
>>> +
>>>       if (f2fs_proc_root)
>>>               sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
>>>
>>> @@ -946,6 +961,12 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
>>>                               victim_bits_seq_show, sb);
>>>       }
>>>       return 0;
>>> +err2:
>>> +     ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
>>> +err1:
>>> +     kobject_put(&sbi->s_kobj);
>>> +     wait_for_completion(&sbi->s_kobj_unregister);
>>> +     return err;
>>>  }
>>>
>>>  void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
>>> @@ -957,6 +978,8 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
>>>               remove_proc_entry("victim_bits", sbi->s_proc);
>>>               remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
>>>       }
>>> +     sysfs_remove_link(&f2fs_kset.kobj, sbi->s_mount_name);
>>> +     ida_simple_remove(&f2fs_mount_ida, sbi->s_mount_id);
>>>       kobject_del(&sbi->s_kobj);
>>>       kobject_put(&sbi->s_kobj);
>>>  }
>>>
> .
> 

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Daeho Jeong]

> On 2020/7/1 15:04, Daeho Jeong wrote:
> > Actually, I want to keep the mount number remaining to the same
> > number, even if it's re-mounted.
>
> Then once there is f2fs umounter, the order will be incorrect...

Actually, we prepared this patch for a strictly controlled system like
Android to easily access the sysfs node for a specific partition like
userdata partition using a specific number.
In this system, we don't worry about another unexpected f2fs umounter
interfering in between unmounting and mounting a partition.

When we are under the condition that we can keep track of how many
times the userdata partition has been re-mounted, we might as well use
the original partition name like "/sys/fs/f2fs/dm-9".
This is for when we couldn't do that.

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Chao Yu]

On 2020/7/1 20:12, Daeho Jeong wrote:
>> On 2020/7/1 15:04, Daeho Jeong wrote:
>>> Actually, I want to keep the mount number remaining to the same
>>> number, even if it's re-mounted.
>>
>> Then once there is f2fs umounter, the order will be incorrect...
> 
> Actually, we prepared this patch for a strictly controlled system like
> Android to easily access the sysfs node for a specific partition like
> userdata partition using a specific number.

I'm not against Android defined interfaces, just be confused about the
behavior that does not fully documented (at least, we should add this
into f2fs doc, and specify this is android specified interface), something
like once one mount point was umounted, that sequential number @x in
'mount_@x" could be reused by later newly mounted point, it breaks the
description: "in the order of mounting filesystem".

> In this system, we don't worry about another unexpected f2fs umounter
> interfering in between unmounting and mounting a partition.
> 
> When we are under the condition that we can keep track of how many
> times the userdata partition has been re-mounted, we might as well use
> the original partition name like "/sys/fs/f2fs/dm-9".
> This is for when we couldn't do that.
> .
> 

Re: [f2fs-dev] [PATCH] f2fs: add symbolic link to kobject in sysfs

[Daeho Jeong]

Got it.

Thanks~

2020년 7월 3일 (금) 오전 11:02, Chao Yu <yuchao0@huawei.com>님이 작성:
>
> On 2020/7/1 20:12, Daeho Jeong wrote:
> >> On 2020/7/1 15:04, Daeho Jeong wrote:
> >>> Actually, I want to keep the mount number remaining to the same
> >>> number, even if it's re-mounted.
> >>
> >> Then once there is f2fs umounter, the order will be incorrect...
> >
> > Actually, we prepared this patch for a strictly controlled system like
> > Android to easily access the sysfs node for a specific partition like
> > userdata partition using a specific number.
>
> I'm not against Android defined interfaces, just be confused about the
> behavior that does not fully documented (at least, we should add this
> into f2fs doc, and specify this is android specified interface), something
> like once one mount point was umounted, that sequential number @x in
> 'mount_@x" could be reused by later newly mounted point, it breaks the
> description: "in the order of mounting filesystem".
>
> > In this system, we don't worry about another unexpected f2fs umounter
> > interfering in between unmounting and mounting a partition.
> >
> > When we are under the condition that we can keep track of how many
> > times the userdata partition has been re-mounted, we might as well use
> > the original partition name like "/sys/fs/f2fs/dm-9".
> > This is for when we couldn't do that.
> > .
> >