Andrew,

Will it be possible to have a macro, something like
is_valid_hugepage_addr, that has the arch. specific definition of
checking the validity (like len > TASK_SIZE etc) of any hugepage addr.
It will make the following code more usable across archs. I know we
could have HAVE_ARCH_HUGETLB_UNMAPPED_AREA to have arch specific thing,
but just thought if a small cahnge in existing function could make this
code widely useable.

In addition, HUGE_PAGE_ALIGNMENT sanity check is also needed in
generic_unmapped_area code for MAP_FIXED cases.

I'm attaching a patch.  For i386, the addr parameter to this function is
not modified.  But other archs like ia64 will do that.

thanks,
rohit




> -----Original Message-----
> From: Andrew Morton [mailto:akpm@digeo.com] 
> Sent: Sunday, February 02, 2003 2:55 AM
> To: davem@redhat.com; rohit.seth@intel.com; 
> davidm@napali.hpl.hp.com; anton@samba.org; 
> wli@holomorphy.com; linux-mm@kvack.org
> Subject: Re: hugepage patches
> 
> 
> 5/4
> 
> get_unmapped_area for hugetlbfs
> 
> Having to specify the mapping address is a pain.  Give 
> hugetlbfs files a file_operations.get_unmapped_area().
> 
> The implementation is in hugetlbfs rather than in arch code 
> because it's probably common to several architectures.  If 
> the architecture has special needs it can define 
> HAVE_ARCH_HUGETLB_UNMAPPED_AREA and go it alone.  Just like 
> HAVE_ARCH_UNMAPPED_AREA.
> 
> 
> 
> Having to specify the mapping address is a pain.  Give 
> hugetlbfs files a file_operations.get_unmapped_area().
> 
> The implementation is in hugetlbfs rather than in arch code 
> because it's probably common to several architectures.  If 
> the architecture has special needs it can define 
> HAVE_ARCH_HUGETLB_UNMAPPED_AREA and go it alone.  Just like 
> HAVE_ARCH_UNMAPPED_AREA.
> 
> 
> 
>  hugetlbfs/inode.c |   46 
> ++++++++++++++++++++++++++++++++++++++++++++--
>  1 files changed, 44 insertions(+), 2 deletions(-)
> 
> diff -puN fs/hugetlbfs/inode.c~hugetlbfs-get_unmapped_area 
> fs/hugetlbfs/inode.c
> --- 25/fs/hugetlbfs/inode.c~hugetlbfs-get_unmapped_area	
> 2003-02-01 01:13:03.000000000 -0800
> +++ 25-akpm/fs/hugetlbfs/inode.c	2003-02-02 
> 01:17:01.000000000 -0800
> @@ -74,6 +74,47 @@ static int hugetlbfs_file_mmap(struct fi
>  }
>  
>  /*
> + * Called under down_write(mmap_sem), page_table_lock is not held */
> +
> +#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
> +unsigned long hugetlb_get_unmapped_area(struct file *file, 
> unsigned long addr,
> +		unsigned long len, unsigned long pgoff, 
> unsigned long flags); #else
> +static unsigned long
> +hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> +		unsigned long len, unsigned long pgoff, 
> unsigned long flags)
> +{
> +	struct mm_struct *mm = current->mm;
> +	struct vm_area_struct *vma;
> +
> +	if (len & ~HPAGE_MASK)
> +		return -EINVAL;
> +	if (len > TASK_SIZE)
> +		return -ENOMEM;
> +
> +	if (addr) {
> +		addr = ALIGN(addr, HPAGE_SIZE);
> +		vma = find_vma(mm, addr);
> +		if (TASK_SIZE - len >= addr &&
> +		    (!vma || addr + len <= vma->vm_start))
> +			return addr;
> +	}
> +
> +	addr = ALIGN(mm->free_area_cache, HPAGE_SIZE);
> +
> +	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
> +		/* At this point:  (!vma || addr < vma->vm_end). */
> +		if (TASK_SIZE - len < addr)
> +			return -ENOMEM;
> +		if (!vma || addr + len <= vma->vm_start)
> +			return addr;
> +		addr = ALIGN(vma->vm_end, HPAGE_SIZE);
> +	}
> +}
> +#endif
> +
> +/*
>   * Read a page. Again trivial. If it didn't already exist
>   * in the page cache, it is zero-filled.
>   */
> @@ -466,8 +507,9 @@ static struct address_space_operations h
>  };
>  
>  struct file_operations hugetlbfs_file_operations = {
> -	.mmap		= hugetlbfs_file_mmap,
> -	.fsync		= simple_sync_file,
> +	.mmap			= hugetlbfs_file_mmap,
> +	.fsync			= simple_sync_file,
> +	.get_unmapped_area	= hugetlb_get_unmapped_area,
>  };
>  
>  static struct inode_operations hugetlbfs_dir_inode_operations = {
> 
> _




>