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Commit 2f89dc12 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
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dax: protect PTE modification on WP fault by radix tree entry lock 

Currently PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite()
has released corresponding radix tree entry lock.  When we want to
writeprotect PTE on cache flush, we need PTE modification to happen
under radix tree entry lock to ensure consistent updates of PTE and
radix tree (standard faults use page lock to ensure this consistency).
So move update of PTE bit into dax_pfn_mkwrite().

Link: http://lkml.kernel.org/r/1479460644-25076-20-git-send-email-jack@suse.cz


Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a6abc2c0

fs/dax.c

+16 −6
Original line number Diff line number Diff line
@@ -783,19 +783,29 @@ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 
{

	struct file *file = vma->vm_file;

	struct address_space *mapping = file->f_mapping;

	void *entry;

	void *entry, **slot;

	pgoff_t index = vmf->pgoff;



	spin_lock_irq(&mapping->tree_lock);

	entry = get_unlocked_mapping_entry(mapping, index, NULL);

	if (!entry || !radix_tree_exceptional_entry(entry))

		goto out;

	radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);

	entry = get_unlocked_mapping_entry(mapping, index, &slot);

	if (!entry || !radix_tree_exceptional_entry(entry)) {

		if (entry)

			put_unlocked_mapping_entry(mapping, index, entry);

out:

		spin_unlock_irq(&mapping->tree_lock);

		return VM_FAULT_NOPAGE;

	}

	radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);

	entry = lock_slot(mapping, slot);

	spin_unlock_irq(&mapping->tree_lock);

	/*

	 * If we race with somebody updating the PTE and finish_mkwrite_fault()

	 * fails, we don't care. We need to return VM_FAULT_NOPAGE and retry

	 * the fault in either case.

	 */

	finish_mkwrite_fault(vmf);

	put_locked_mapping_entry(mapping, index, entry);

	return VM_FAULT_NOPAGE;

}

EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);



static bool dax_range_is_aligned(struct block_device *bdev,

mm/memory.c

+1 −1
Original line number Diff line number Diff line
@@ -2315,7 +2315,7 @@ static int wp_pfn_shared(struct vm_fault *vmf) 
		pte_unmap_unlock(vmf->pte, vmf->ptl);

		vmf->flags |= FAULT_FLAG_MKWRITE;

		ret = vma->vm_ops->pfn_mkwrite(vma, vmf);

		if (ret & VM_FAULT_ERROR)

		if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))

			return ret;

		return finish_mkwrite_fault(vmf);

	}