Re: [patch] do_no_pfn handler

[Nick Piggin]

Jes Sorensen wrote:
> +static int do_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
> +		     unsigned long address, pte_t *page_table, pmd_t *pmd,
> +		     int write_access)
> +{
> +	spinlock_t *ptl;
> +	pte_t entry;
> +	long pfn;
> +	int ret = VM_FAULT_MINOR;
> +
> +	pte_unmap(page_table);
> +	BUG_ON(!(vma->vm_flags & VM_PFNMAP));
> +
> +	pfn = vma->vm_ops->nopfn(vma, address & PAGE_MASK, &ret);
> +	if (pfn == -ENOMEM)
> +		return VM_FAULT_OOM;
> +	if (pfn == -EFAULT)
> +		return VM_FAULT_SIGBUS;
> +	if (pfn < 0)
> +		return VM_FAULT_SIGBUS;
> +
> +	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
> +
> +	entry = pfn_pte(pfn, vma->vm_page_prot);
> +	if (write_access)
> +		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> +	set_pte_at(mm, address, page_table, entry);
> +

Should you recheck to make sure nobody else faulted this in
before it was relocked? Doesn't seem to matter in this case,
but it would be more consistent with the other fault handlers.

--
SUSE Labs, Novell Inc.
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