linux-kernel - Re: [PATCH 2/6] shmem: rename functions that are memfd-related

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Date:   Fri, 3 Nov 2017 09:22:06 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Marc-André Lureau <marcandre.lureau@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        aarcange@...hat.com, hughd@...gle.com, nyc@...omorphy.com
Subject: Re: [PATCH 2/6] shmem: rename functions that are memfd-related

On 11/03/2017 09:02 AM, Marc-André Lureau wrote:
> Hi
> 
> ----- Original Message -----
>> On 10/31/2017 11:40 AM, Marc-André Lureau wrote:
>>> Those functions are called for memfd files, backed by shmem or
>>> hugetlb (the next patches will handle hugetlb).
>>>
>>> Signed-off-by: Marc-André Lureau <marcandre.lureau@...hat.com>
>>> ---
>>>  fs/fcntl.c               |  2 +-
>>>  include/linux/shmem_fs.h |  4 ++--
>>>  mm/shmem.c               | 10 +++++-----
>>>  3 files changed, 8 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/fcntl.c b/fs/fcntl.c
>>> index 448a1119f0be..752c23743616 100644
>>> --- a/fs/fcntl.c
>>> +++ b/fs/fcntl.c
>>> @@ -417,7 +417,7 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned
>>> long arg,
>>>  		break;
>>>  	case F_ADD_SEALS:
>>>  	case F_GET_SEALS:
>>> -		err = shmem_fcntl(filp, cmd, arg);
>>> +		err = memfd_fcntl(filp, cmd, arg);
>>>  		break;
>>>  	case F_GET_RW_HINT:
>>>  	case F_SET_RW_HINT:
>>> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
>>> index 557d0c3b6eca..0dac8c0f4aa4 100644
>>> --- a/include/linux/shmem_fs.h
>>> +++ b/include/linux/shmem_fs.h
>>> @@ -109,11 +109,11 @@ extern void shmem_uncharge(struct inode *inode, long
>>> pages);
>>>  
>>>  #ifdef CONFIG_TMPFS
>>>  
>>> -extern long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long
>>> arg);
>>> +extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long
>>> arg);
>>>  
>>>  #else
>>>  
>>> -static inline long shmem_fcntl(struct file *f, unsigned int c, unsigned
>>> long a)
>>> +static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned
>>> long a)
>>>  {
>>>  	return -EINVAL;
>>>  }
>>
>> Do we want memfd_fcntl() to work for hugetlbfs if CONFIG_TMPFS is not
>> defined?  I admit that having CONFIG_HUGETLBFS defined without CONFIG_TMPFS
>> is unlikely, but I think possible.  Based on the above #ifdef/#else, I
>> think hugetlbfs seals will not work if CONFIG_TMPFS is not defined.
> 
> Good point, memfd_create() will not exists either.
> 
> I think this is a separate concern, and preexisting from this patch series though.

Ah yes.  I should have addressed this when adding hugetlbfs memfd_create
support.

Of course, one 'simple' way to address this would be to make CONFIG_HUGETLBFS
depend on CONFIG_TMPFS.  Not sure what people think about this?

> Ack the function renaming part?

Yes, the remaining code looks fine to me.

-- 
Mike Kravetz

> 
>> --
>> Mike Kravetz
>>
>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>> index 37260c5e12fa..b7811979611f 100644
>>> --- a/mm/shmem.c
>>> +++ b/mm/shmem.c
>>> @@ -2722,7 +2722,7 @@ static int shmem_wait_for_pins(struct address_space
>>> *mapping)
>>>  		     F_SEAL_GROW | \
>>>  		     F_SEAL_WRITE)
>>>  
>>> -static int shmem_add_seals(struct file *file, unsigned int seals)
>>> +static int memfd_add_seals(struct file *file, unsigned int seals)
>>>  {
>>>  	struct inode *inode = file_inode(file);
>>>  	struct shmem_inode_info *info = SHMEM_I(inode);
>>> @@ -2792,7 +2792,7 @@ static int shmem_add_seals(struct file *file,
>>> unsigned int seals)
>>>  	return error;
>>>  }
>>>  
>>> -static int shmem_get_seals(struct file *file)
>>> +static int memfd_get_seals(struct file *file)
>>>  {
>>>  	if (file->f_op != &shmem_file_operations)
>>>  		return -EINVAL;
>>> @@ -2800,7 +2800,7 @@ static int shmem_get_seals(struct file *file)
>>>  	return SHMEM_I(file_inode(file))->seals;
>>>  }
>>>  
>>> -long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
>>> +long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
>>>  {
>>>  	long error;
>>>  
>>> @@ -2810,10 +2810,10 @@ long shmem_fcntl(struct file *file, unsigned int
>>> cmd, unsigned long arg)
>>>  		if (arg > UINT_MAX)
>>>  			return -EINVAL;
>>>  
>>> -		error = shmem_add_seals(file, arg);
>>> +		error = memfd_add_seals(file, arg);
>>>  		break;
>>>  	case F_GET_SEALS:
>>> -		error = shmem_get_seals(file);
>>> +		error = memfd_get_seals(file);
>>>  		break;
>>>  	default:
>>>  		error = -EINVAL;
>>>
>>
>> --
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