Re: [PATCH v2 2/5] dax: fallback from pmd to pte on error

[Jeff Moyer]

Vishal Verma <vishal.l.verma@xxxxxxxxx> writes:

> From: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> In preparation for consulting a badblocks list in pmem_direct_access(),
> teach dax_pmd_fault() to fallback rather than fail immediately upon
> encountering an error.  The thought being that reducing the span of the
> dax request may avoid the error region.
>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>

> ---
>  fs/dax.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 90322eb..ec6417b 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -945,8 +945,8 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
>  		long length = dax_map_atomic(bdev, &dax);
>  
>  		if (length < 0) {
> -			result = VM_FAULT_SIGBUS;
> -			goto out;
> +			dax_pmd_dbg(&bh, address, "dax-error fallback");
> +			goto fallback;
>  		}
>  		if (length < PMD_SIZE) {
>  			dax_pmd_dbg(&bh, address, "dax-length too small");