[RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[zhongjiang]

From: zhong jiang <zhongjiang@huawei.com>

Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")'
bring in the mainline. mount hugetlbfs will result in the following issue.

mount: unknown filesystme type 'hugetlbfs'

because previous patch remove the module_alias_fs, when we mount the fs type,
the caller get_fs_type can not find the filesystem.

The patch just recover the module_alias_fs to identify the hugetlbfs.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
---
 fs/hugetlbfs/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 4fb7b10..b63e7de 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -35,6 +35,7 @@
 #include <linux/security.h>
 #include <linux/magic.h>
 #include <linux/migrate.h>
+#include <linux/module.h>
 #include <linux/uio.h>
 
 #include <asm/uaccess.h>
@@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
 	.mount		= hugetlbfs_mount,
 	.kill_sb	= kill_litter_super,
 };
+MODULE_ALIAS_FS("hugetlbfs");
 
 static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
 
-- 
1.8.3.1

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Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[zhong jiang]

On 2016/10/29 14:08, zhongjiang wrote:
> From: zhong jiang <zhongjiang@huawei.com>
>
> Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")'
> bring in the mainline. mount hugetlbfs will result in the following issue.
>
> mount: unknown filesystme type 'hugetlbfs'
>
> because previous patch remove the module_alias_fs, when we mount the fs type,
> the caller get_fs_type can not find the filesystem.
>
> The patch just recover the module_alias_fs to identify the hugetlbfs.
>
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> ---
>  fs/hugetlbfs/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 4fb7b10..b63e7de 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -35,6 +35,7 @@
>  #include <linux/security.h>
>  #include <linux/magic.h>
>  #include <linux/migrate.h>
> +#include <linux/module.h>
>  #include <linux/uio.h>
>  
>  #include <asm/uaccess.h>
> @@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
>  	.mount		= hugetlbfs_mount,
>  	.kill_sb	= kill_litter_super,
>  };
> +MODULE_ALIAS_FS("hugetlbfs");
>  
>  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
>  
 please ignore the patch,  It have been fixed.

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Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[Andrew Morton]

On Sat, 29 Oct 2016 14:08:31 +0800 zhongjiang <zhongjiang@huawei.com> wrote:

> From: zhong jiang <zhongjiang@huawei.com>
> 
> Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")'
> bring in the mainline. mount hugetlbfs will result in the following issue.
> 
> mount: unknown filesystme type 'hugetlbfs'
> 
> because previous patch remove the module_alias_fs, when we mount the fs type,
> the caller get_fs_type can not find the filesystem.
> 
> The patch just recover the module_alias_fs to identify the hugetlbfs.

hm, 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly
non-modular") was merged almost a year ago.  And you are apparently the
first person to discover this regression.  Can you think why that is?

> index 4fb7b10..b63e7de 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -35,6 +35,7 @@
>  #include <linux/security.h>
>  #include <linux/magic.h>
>  #include <linux/migrate.h>
> +#include <linux/module.h>
>  #include <linux/uio.h>
>  
>  #include <asm/uaccess.h>
> @@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
>  	.mount		= hugetlbfs_mount,
>  	.kill_sb	= kill_litter_super,
>  };
> +MODULE_ALIAS_FS("hugetlbfs");
>  
>  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
>  

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Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[Paul Gortmaker]

[Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted] On 03/11/2016 (Thu 12:17) Andrew Morton wrote:

> On Sat, 29 Oct 2016 14:08:31 +0800 zhongjiang <zhongjiang@huawei.com> wrote:
> 
> > From: zhong jiang <zhongjiang@huawei.com>
> > 
> > Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")'
> > bring in the mainline. mount hugetlbfs will result in the following issue.
> > 
> > mount: unknown filesystme type 'hugetlbfs'

The fact that the above has a typo makes me doubt it was real output
from "mount".   In any case, that just means they didn't enable the
Kconfig option for it and hence it is not in /proc/filesystems as they
can easily verify.

> > 
> > because previous patch remove the module_alias_fs, when we mount the fs type,
> > the caller get_fs_type can not find the filesystem.
> > 
> > The patch just recover the module_alias_fs to identify the hugetlbfs.
> 
> hm, 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly
> non-modular") was merged almost a year ago.  And you are apparently the
> first person to discover this regression.  Can you think why that is?

Agreed -- I'd like to know just how this conclusion was reached.  Maybe
they are running some out-of-tree patches to make it modular?  Who
knows.  It would be nice if we hear back, but I don't have high hopes.

In any case, 3e89e1c5ea84 commit log says:

    Also note that MODULE_ALIAS is a no-op for non-modular code.

This isn't fundamentally hard to verify; the macros are:

#define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)

#define MODULE_ALIAS(_alias) MODULE_INFO(alias, _alias)

#define MODULE_INFO(tag, info) __MODULE_INFO(tag, tag, info)

...and then finally:

#ifdef MODULE
#define __MODULE_INFO(tag, name, info)                                    \
static const char __UNIQUE_ID(name)[]                                     \
  __used __attribute__((section(".modinfo"), unused, aligned(1)))         \
  = __stringify(tag) "=" info
#else  /* !MODULE */
/* This struct is here for syntactic coherency, it is not used */
#define __MODULE_INFO(tag, name, info)                                    \
  struct __UNIQUE_ID(name) {}
#endif

...so a commit like this would have to explain how the patch does anything in
the !MODULE case, when the syntax comment above even indicates it is not used.

I remember this commit since there was patch order issue that the kbuild
robot uncovered (as listed in the commit log) in an earlier version of it.

So I can assure the patch poster that hugetlbfs was mounted for testing,
and they should revisit the logic that led to this no-op patch.

Paul.
--

> 
> > index 4fb7b10..b63e7de 100644
> > --- a/fs/hugetlbfs/inode.c
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -35,6 +35,7 @@
> >  #include <linux/security.h>
> >  #include <linux/magic.h>
> >  #include <linux/migrate.h>
> > +#include <linux/module.h>
> >  #include <linux/uio.h>
> >  
> >  #include <asm/uaccess.h>
> > @@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
> >  	.mount		= hugetlbfs_mount,
> >  	.kill_sb	= kill_litter_super,
> >  };
> > +MODULE_ALIAS_FS("hugetlbfs");
> >  
> >  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
> >  
> 

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Re: [RFC PATCH] hugetlbfs: fix the hugetlbfs can not be mounted

[zhong jiang]

On 2016/11/4 3:17, Andrew Morton wrote:
> On Sat, 29 Oct 2016 14:08:31 +0800 zhongjiang <zhongjiang@huawei.com> wrote:
>
>> From: zhong jiang <zhongjiang@huawei.com>
>>
>> Since 'commit 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly non-modular")'
>> bring in the mainline. mount hugetlbfs will result in the following issue.
>>
>> mount: unknown filesystme type 'hugetlbfs'
>>
>> because previous patch remove the module_alias_fs, when we mount the fs type,
>> the caller get_fs_type can not find the filesystem.
>>
>> The patch just recover the module_alias_fs to identify the hugetlbfs.
> hm, 3e89e1c5ea84 ("hugetlb: make mm and fs code explicitly
> non-modular") was merged almost a year ago.  And you are apparently the
> first person to discover this regression.  Can you think why that is?
  when I pull the upstream patch in 4.9-rc2. I find that I cannot mount the hugetlbfs.
  but when I pull  the upstream remain patch in the next day.  I test again. it  work well.
  so I reply the mail right now,  please ignore the patch.  The detailed reason is not digged.

  I am sorry for wasting your time.

  Thanks you
  zhongjiang
>> index 4fb7b10..b63e7de 100644
>> --- a/fs/hugetlbfs/inode.c
>> +++ b/fs/hugetlbfs/inode.c
>> @@ -35,6 +35,7 @@
>>  #include <linux/security.h>
>>  #include <linux/magic.h>
>>  #include <linux/migrate.h>
>> +#include <linux/module.h>
>>  #include <linux/uio.h>
>>  
>>  #include <asm/uaccess.h>
>> @@ -1209,6 +1210,7 @@ static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
>>  	.mount		= hugetlbfs_mount,
>>  	.kill_sb	= kill_litter_super,
>>  };
>> +MODULE_ALIAS_FS("hugetlbfs");
>>  
>>  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
>>  
>
> .
>


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