On Tue, Sep 27, 2016 at 06:08:23PM +0200, Jan Kara wrote:
> 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 consisten updates of PTE and radix
consistent
> tree (standard faults use page lock to ensure this consistency). So move
> update of PTE bit into dax_pfn_mkwrite().
>
> Signed-off-by: Jan Kara <[email protected]>
> ---
> fs/dax.c | 22 ++++++++++++++++------
> mm/memory.c | 2 +-
> 2 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index c6cadf8413a3..a2d3781c9f4e 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1163,17 +1163,27 @@ 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;
> + entry = get_unlocked_mapping_entry(mapping, index, &slot);
> + if (!entry || !radix_tree_exceptional_entry(entry)) {
> + if (entry)
> + put_unlocked_mapping_entry(mapping, index, entry);
I don't think you need this call to put_unlocked_mapping_entry(). If we get
in here we know that 'entry' is a page cache page, in which case
put_unlocked_mapping_entry() will just return without doing any work.
With that nit & the spelling error above:
Reviewed-by: Ross Zwisler <[email protected]>
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