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Date: Tue, 2 Feb 2010 10:39:30 -0600
From: Robin Holt <holt@sgi.com>
Subject: Re: [RFP-V2 0/3] Make mmu_notifier_invalidate_range_start able to
 sleep.
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Robin Holt <holt@sgi.com>, Christoph Hellwig <hch@infradead.org>, Andrew Morton <akpm@linux-foundation.org>, Jack Steiner <steiner@sgi.com>, linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>

On Tue, Feb 02, 2010 at 05:01:46PM +0100, Andrea Arcangeli wrote:
> On Tue, Feb 02, 2010 at 09:21:42AM -0600, Robin Holt wrote:
> > unmap_mapping_range_vma would then unlock the i_mmap_lock, call
> > _inv_range_start(atomic==0) which would clear all the remote page tables
> > and TLBs.  It would then reaquire the i_mmap_lock and retry.
> 
> I guess you missed why we hold the i_mmap_lock there... it's not like
> gratuitous locking complication there's an actual reason why it's
> taken, and it's to avoid the vma to be freed from under you:

Oversight on my part.  Sorry.

Will this work?
static int unmap_mapping_range_vma(struct vm_area_struct *vma,
...
	if (need_unlocked_invalidate) {
		mm = vma->vm_mm;
		atomic_inc(&mm->mm_users);
	}
	spin_unlock(details->i_mmap_lock);
	if (need_unlocked_invalidate) {
		/*
		 * zap_page_range failed to make any progress because the
		 * mmu_notifier_invalidate_range_start was called atomically
		 * while the callee needed to sleep.  In that event, we
		 * make the callout while the i_mmap_lock is released.
		 */
		mmu_notifier_invalidate_range_start(mm, start_addr, end_addr, 0);
		mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
		mmput(mm);
	}
	cond_resched();
	spin_lock(details->i_mmap_lock);
	return -EINTR;

Robin

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