Re: [PATCH 6/7] mm: allow ->page_mkwrite to do retries

[Dave Chinner]

On Thu, Oct 18, 2018 at 04:23:17PM -0400, Josef Bacik wrote:
> Before we didn't set the retry flag on our vm_fault.  We want to allow
> file systems to drop the mmap_sem if they so choose, so set this flag
> and deal with VM_FAULT_RETRY appropriately.
> 
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ---
>  mm/memory.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 433075f722ea..c5e81edd94f9 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2384,11 +2384,13 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
>  	unsigned int old_flags = vmf->flags;
>  
>  	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
> +	vmf->flags |= old_flags & FAULT_FLAG_ALLOW_RETRY;
>  
>  	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
>  	/* Restore original flags so that caller is not surprised */
>  	vmf->flags = old_flags;


> -	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
> +	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
> +			    VM_FAULT_RETRY)))

Mess.

#define __FAIL_FLAGS	(VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)
	if (ret & __FAIL_FLAGS)

Should kill the unlikely() at the same time.

-Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx