On Tue, Sep 27, 2016 at 06:08:14PM +0200, Jan Kara wrote:
> Move final handling of COW faults from generic code into DAX fault
> handler. That way generic code doesn't have to be aware of peculiarities
> of DAX locking so remove that knowledge.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/dax.c | 22 ++++++++++++++++------
> include/linux/dax.h | 7 -------
> include/linux/mm.h | 9 +--------
> mm/memory.c | 14 ++++----------
> 4 files changed, 21 insertions(+), 31 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0dc251ca77b8..b1c503930d1d 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -876,10 +876,15 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
> goto unlock_entry;
> if (!radix_tree_exceptional_entry(entry)) {
> vmf->page = entry;
> - return VM_FAULT_LOCKED;
> + if (unlikely(PageHWPoison(entry))) {
> + put_locked_mapping_entry(mapping, vmf->pgoff,
> + entry);
> + return VM_FAULT_HWPOISON;
> + }
> }
> - vmf->entry = entry;
> - return VM_FAULT_DAX_LOCKED;
> + error = finish_fault(vmf);
> + put_locked_mapping_entry(mapping, vmf->pgoff, entry);
> + return error ? error : VM_FAULT_DONE_COW;
> }
>
> if (!buffer_mapped(&bh)) {
> @@ -1430,10 +1435,15 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
> goto unlock_entry;
> if (!radix_tree_exceptional_entry(entry)) {
> vmf->page = entry;
In __do_fault() we explicitly clear vmf->page in the case where PageHWPoison()
is set. I think we can get the same behavior here by moving the call that
sets vmf->page after the PageHWPoison() check.
> - return VM_FAULT_LOCKED;
> + if (unlikely(PageHWPoison(entry))) {
> + put_locked_mapping_entry(mapping, vmf->pgoff,
> + entry);
> + return VM_FAULT_HWPOISON;
> + }
> }
> - vmf->entry = entry;
> - return VM_FAULT_DAX_LOCKED;
I think we're missing a call to
__SetPageUptodate(new_page);
before finish_fault()? This call currently lives in do_cow_fault(), and
is part of the path that we don't skip as part of the VM_FAULT_DAX_LOCKED
logic.
Both of these comments apply equally to the iomap_dax_fault() code.
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