Re: [PATCH 2/2] percpu: fix iteration to prevent skipping over block

[Tejun Heo]

On Wed, Sep 27, 2017 at 04:35:00PM -0500, Dennis Zhou wrote:
> The iterator functions pcpu_next_md_free_region and
> pcpu_next_fit_region use the block offset to determine if they have
> checked the area in the prior iteration. However, this causes an issue
> when the block offset is greater than subsequent block contig hints. If
> within the iterator it moves to check subsequent blocks, it may fail in
> the second predicate due to the block offset not being cleared. Thus,
> this causes the allocator to skip over blocks leading to false failures
> when allocating from the reserved chunk. While this happens in the
> general case as well, it will only fail if it cannot allocate a new
> chunk.
> 
> This patch resets the block offset to 0 to pass the second predicate
> when checking subseqent blocks within the iterator function.
> 
> Signed-off-by: Dennis Zhou <dennisszhou@xxxxxxxxx>
> Reported-by: Luis Henriques <lhenriques@xxxxxxxx>

Luis, can you please verify that this fixes the allocaiton failure you
were seeing?

Thanks.

-- 
tejun