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SubjectRe: [PATCH 11/12] device-dax: Add dis-contiguous resource support
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On 3/23/20 11:55 PM, Dan Williams wrote:
> @@ -561,13 +580,26 @@ static int __alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
> if (start == U64_MAX)
> return -EINVAL;
>
> + ranges = krealloc(dev_dax->ranges, sizeof(*ranges)
> + * (dev_dax->nr_range + 1), GFP_KERNEL);
> + if (!ranges)
> + return -ENOMEM;
> +
> alloc = __request_region(res, start, size, dev_name(dev), 0);
> - if (!alloc)
> + if (!alloc) {
> + kfree(ranges);
> return -ENOMEM;
> + }

Noticed this yesterday while looking at alloc_dev_dax_range().

Is it correct to free @ranges here on __request_region failure?

IIUC krealloc() would free dev_dax->ranges if it succeeds, leaving us without
any valid ranges if __request_region failure case indeed frees @ranges. These
@ranges are being used afterwards when we delete the interface and free the
assigned regions. Perhaps we should remove the kfree() above and set
dev_dax->ranges instead before __request_region; or alternatively change the
call order between krealloc and __request_region? FWIW, krealloc checks if the
object being reallocated already meets the requested size, so perhaps there's no
harm with going with the former.

Joao

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