Re: [RFC PATCH for -mm 5/5] fix mlock return value for mm

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Mon, 2008-08-11 at 16:43 +0900, KOSAKI Motohiro wrote:
> > Now, __mlock_vma_pages_range() ignore return value of __get_user_pages().
> > We shouldn't do that.
> 
> Oops, sorry.
> I sent older version, I resend it.
> 
> Definitly, I should learn an correct operation of quilt ;)
> 
> 
> --------------------------------------------------------------
> Now, __mlock_vma_pages_range() ignore return value of __get_user_pages().
> We shouldn't do that.

Could you explain, in comments or patch description, why, after patching
__mlock_vma_pages_range() top return mlock() appropriate values for
__get_user_pages() failures, you then ignore the return value of
__mlock_vma_pages_range() in mlock_vma_pages_range() [last 4 hunks]?  Is
it because mlock_vma_pages_range() is called from mmap(), mremap(), etc,
and not from mlock()?

Lee
> 
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> 
> ---
>  mm/mlock.c |   32 ++++++++++++++++++++++++--------
>  1 file changed, 24 insertions(+), 8 deletions(-)
> 
> Index: b/mm/mlock.c
> ===================================================================
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -165,8 +165,9 @@ static int __mlock_vma_pages_range(struc
>  	unsigned long addr = start;
>  	struct page *pages[16]; /* 16 gives a reasonable batch */
>  	int nr_pages = (end - start) / PAGE_SIZE;
> -	int ret;
> +	int ret = 0;
>  	int gup_flags = 0;
> +	int ret2 = 0;
>  
>  	VM_BUG_ON(start & ~PAGE_MASK);
>  	VM_BUG_ON(end   & ~PAGE_MASK);
> @@ -249,9 +250,23 @@ static int __mlock_vma_pages_range(struc
>  		}
>  	}
>  
> +	/*
> +	  SUSv3 require following return value to mlock
> +	  - invalid addr generate to ENOMEM.
> +	  - out of memory generate EAGAIN.
> +	*/
> +	if (ret < 0) {
> +		if (ret == -EFAULT)
> +			ret2 = -ENOMEM;
> +		else if (ret == -ENOMEM)
> +			ret2 = -EAGAIN;
> +		else
> +			ret2 = ret;
> +	}
> +
>  	lru_add_drain_all();	/* to update stats */
>  
> -	return 0;	/* count entire vma as locked_vm */
> +	return ret2;	/* count entire vma as locked_vm */
>  }
>  
>  #else /* CONFIG_UNEVICTABLE_LRU */
> @@ -263,9 +278,11 @@ static int __mlock_vma_pages_range(struc
>  				   unsigned long start, unsigned long end,
>  				   int mlock)
>  {
> +	int ret = 0;
> +
>  	if (mlock && (vma->vm_flags & VM_LOCKED))
> -		make_pages_present(start, end);
> -	return 0;
> +		ret = make_pages_present(start, end);
> +	return ret;
>  }
>  #endif /* CONFIG_UNEVICTABLE_LRU */
>  
> @@ -276,7 +293,6 @@ int mlock_vma_pages_range(struct vm_area
>  			unsigned long start, unsigned long end)
>  {
>  	struct mm_struct *mm = vma->vm_mm;
> -	int error = 0;
>  	BUG_ON(!(vma->vm_flags & VM_LOCKED));
>  
>  	/*
> @@ -289,7 +305,7 @@ int mlock_vma_pages_range(struct vm_area
>  			is_vm_hugetlb_page(vma) ||
>  			vma == get_gate_vma(current))) {
>  		downgrade_write(&mm->mmap_sem);
> -		error = __mlock_vma_pages_range(vma, start, end, 1);
> +		__mlock_vma_pages_range(vma, start, end, 1);
>  		up_read(&mm->mmap_sem);
>  		/* vma can change or disappear */
>  		down_write(&mm->mmap_sem);
> @@ -297,7 +313,7 @@ int mlock_vma_pages_range(struct vm_area
>  		/* non-NULL vma must contain @start, but need to check @end */
>  		if (!vma ||  end > vma->vm_end)
>  			return -ENOMEM;
> -		return error;
> +		return 0;
>  	}
>  
>  	/*
> @@ -309,7 +325,7 @@ int mlock_vma_pages_range(struct vm_area
>  
>  no_mlock:
>  	vma->vm_flags &= ~VM_LOCKED;	/* and don't come back! */
> -	return error;			/* pages NOT mlocked */
> +	return 0;			/* pages NOT mlocked */
>  }
>  
> 
> 
> 
> 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>