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Re: [PATCH v2 3/5] dax: enable dax in the presence of known media errors

To: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Subject: Re: [PATCH v2 3/5] dax: enable dax in the presence of known media errors (badblocks)
From: Jeff Moyer <jmoyer@xxxxxxxxxx>
Date: Fri, 15 Apr 2016 10:56:10 -0400
Cc: linux-nvdimm@xxxxxxxxxxx, Jens Axboe <axboe@xxxxxx>, Jan Kara <jack@xxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-block@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1459303190-20072-4-git-send-email-vishal.l.verma@xxxxxxxxx> (Vishal Verma's message of "Tue, 29 Mar 2016 19:59:48 -0600")
References: <1459303190-20072-1-git-send-email-vishal.l.verma@xxxxxxxxx> <1459303190-20072-4-git-send-email-vishal.l.verma@xxxxxxxxx>
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)
Vishal Verma <vishal.l.verma@xxxxxxxxx> writes:

> From: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> 1/ If a mapping overlaps a bad sector fail the request.
>
> 2/ Do not opportunistically report more dax-capable capacity than is
>    requested when errors present.
>
> [vishal: fix a conflict with system RAM collision patches]
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>

> ---
>  block/ioctl.c         | 9 ---------
>  drivers/nvdimm/pmem.c | 8 ++++++++
>  2 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index d8996bb..cd7f392 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -423,15 +423,6 @@ bool blkdev_dax_capable(struct block_device *bdev)
>                       || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
>               return false;
>  
> -     /*
> -      * If the device has known bad blocks, force all I/O through the
> -      * driver / page cache.
> -      *
> -      * TODO: support finer grained dax error handling
> -      */
> -     if (disk->bb && disk->bb->count)
> -             return false;
> -
>       return true;
>  }
>  #endif
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index da10554..eac5f93 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -174,9 +174,17 @@ static long pmem_direct_access(struct block_device *bdev,
>       struct pmem_device *pmem = bdev->bd_disk->private_data;
>       resource_size_t offset = sector * 512 + pmem->data_offset;
>  
> +     if (unlikely(is_bad_pmem(&pmem->bb, sector, dax->size)))
> +             return -EIO;
>       dax->addr = pmem->virt_addr + offset;
>       dax->pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
>  
> +     /*
> +      * If badblocks are present, limit known good range to the
> +      * requested range.
> +      */
> +     if (unlikely(pmem->bb.count))
> +             return dax->size;
>       return pmem->size - pmem->pfn_pad - offset;
>  }

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