linux-kernel - RE: [PATCH 01/12] percpu: update free path with correct new free region

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Date:   Sat, 2 Mar 2019 12:56:46 +0000
From:   Peng Fan <peng.fan@....com>
To:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>
CC:     Vlad Buslov <vladbu@...lanox.com>,
        "kernel-team@...com" <kernel-team@...com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 01/12] percpu: update free path with correct new free
 region



> -----Original Message-----
> From: owner-linux-mm@...ck.org [mailto:owner-linux-mm@...ck.org] On
> Behalf Of Dennis Zhou
> Sent: 2019年2月28日 10:18
> To: Dennis Zhou <dennis@...nel.org>; Tejun Heo <tj@...nel.org>; Christoph
> Lameter <cl@...ux.com>
> Cc: Vlad Buslov <vladbu@...lanox.com>; kernel-team@...com;
> linux-mm@...ck.org; linux-kernel@...r.kernel.org
> Subject: [PATCH 01/12] percpu: update free path with correct new free region
> 
> When updating the chunk's contig_hint on the free path of a hint that does not
> touch the page boundaries, it was incorrectly using the starting offset of the
> free region and the block's contig_hint. This could lead to incorrect
> assumptions about fit given a size and better alignment of the start. Fix this by
> using (end - start) as this is only called when updating a hint within a block.
> 
> Signed-off-by: Dennis Zhou <dennis@...nel.org>
> ---
>  mm/percpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index db86282fd024..53bd79a617b1 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -871,7 +871,7 @@ static void pcpu_block_update_hint_free(struct
> pcpu_chunk *chunk, int bit_off,
>  		pcpu_chunk_refresh_hint(chunk);
>  	else
>  		pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
> -				  s_block->contig_hint);
> +				  end - start);
>  }

Reviewed-by: Peng Fan <peng.fan@....com>

> 
>  /**
> --
> 2.17.1