From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Date: Tue, 18 Feb 2003 10:43:35 +0000 Subject: Re: [Discontig-devel] Re: [Linux-ia64] Re: 2.5.59 & mmap_sem Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org William Lee Irwin III wrote: > > On Tue, Feb 18, 2003 at 09:46:31AM +0100, Xavier Bru wrote: > > Thanks for your answers. > > You are right, we do not need a page structure for mapping /dev/mem in > > IO space (I am not a mm expert :-). > > Here after a possible patch that allows the Xserver running on the NUMA > > platform. (We had the same problem on Azusa). > > Looks perfectly reasonable to me. Other discontig/NUMA implementations > are likely to run into the same issue. > > You might want to send this on to lkml and cc: akpm, he's pretty much > the final destination wrt. VM patches and 2.5. > I'd prefer to do this at the vma level if poss. Given that mmap_mem() has set VM_RESERVED against the VMA, it should be sufficient to do diff -puN mm/memory.c~a mm/memory.c --- 25/mm/memory.c~a 2003-02-18 02:40:01.000000000 -0800 +++ 25-akpm/mm/memory.c 2003-02-18 02:40:18.000000000 -0800 @@ -211,6 +211,9 @@ int copy_page_range(struct mm_struct *ds unsigned long cow; struct pte_chain *pte_chain = NULL; + if (vma->vm_flags & (VM_RESERVED|VM_IO)) + return 0; + if (is_vm_hugetlb_page(vma)) return copy_hugetlb_page_range(dst, src, vma); diff -puN fs/hugetlbfs/inode.c~a fs/hugetlbfs/inode.c --- 25/fs/hugetlbfs/inode.c~a 2003-02-18 02:42:47.000000000 -0800 +++ 25-akpm/fs/hugetlbfs/inode.c 2003-02-18 02:42:55.000000000 -0800 @@ -63,7 +63,7 @@ static int hugetlbfs_file_mmap(struct fi down(&inode->i_sem); UPDATE_ATIME(inode); - vma->vm_flags |= VM_HUGETLB | VM_RESERVED; + vma->vm_flags |= VM_HUGETLB; vma->vm_ops = &hugetlb_vm_ops; ret = hugetlb_prefault(mapping, vma); len = (loff_t)(vma->vm_end - vma->vm_start) + _ The semantics (and usage!) of the VM_foo flags are rather vague. It needs definiton, and an audit.