linux-ext4 - Re: [PATCH v2 3/5] dax: enable dax in the presence of known media errors (badblocks)

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Date:	Fri, 15 Apr 2016 10:56:10 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Vishal Verma <vishal.l.verma@...el.com>
Cc:	linux-nvdimm@...1.01.org, Jens Axboe <axboe@...com>,
	Jan Kara <jack@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Dave Chinner <david@...morbit.com>,
	linux-kernel@...r.kernel.org, xfs@....sgi.com,
	linux-block@...r.kernel.org, linux-mm@...ck.org,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 3/5] dax: enable dax in the presence of known media errors (badblocks)

Vishal Verma <vishal.l.verma@...el.com> writes:

> From: Dan Williams <dan.j.williams@...el.com>
>
> 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@...el.com>

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>

> ---
>  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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