Re: [PATCH] lib/dma-debug: fix bucket_find_contain

From: Andrew Morton
Date: Thu Mar 19 2015 - 18:09:10 EST


On Mon, 16 Mar 2015 19:24:29 +0100 (CET) Sebastian Ott <sebott@xxxxxxxxxxxxxxxxxx> wrote:

> bucket_find_contain will search the bucket list for a dma_debug_entry. When
> the entry isn't found it needs to search other buckets too, since only the
> start address of a dma range is hashed (which might be in a different bucket).
>
> A copy of the dma_debug_entry is used to get the previous hash bucket but when
> its list is searched the original dma_debug_entry is to be used not its
> modified copy.
>
> This fixes false "device driver tries to sync DMA memory it has not allocated"
> warnings.

The changelog doesn't help me understand how serious this is. A 4.0
thing? -stable?

> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -361,7 +361,7 @@ static struct dma_debug_entry *bucket_fi
> unsigned int range = 0;
>
> while (range <= max_range) {
> - entry = __hash_bucket_find(*bucket, &index, containing_match);
> + entry = __hash_bucket_find(*bucket, ref, containing_match);
>
> if (entry)
> return entry;

This code just got more confusing :( Are you sure we aren't supposed to
use `ref' in bucket_find_contain()'s call to get_hash_bucket()?

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