linux-kernel - Re: [PATCH 7/7] btrfs: fix a wrong error check in add_ra_bio

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Message-ID: <AANLkTim+U2s5-vHhmPqam9wj0+0_=01bq3JjnR=xB8T2@mail.gmail.com>
Date:	Thu, 29 Jul 2010 18:38:39 +0800
From:	"Yan, Zheng" <zheng.yan@...cle.com>
To:	miaox@...fujitsu.com
Cc:	Chris Mason <chris.mason@...cle.com>,
	Linux Btrfs <linux-btrfs@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] btrfs: fix a wrong error check in add_ra_bio_pages()

2010/7/29 Miao Xie <miaox@...fujitsu.com>:
> From: Liu Bo <liubo2009@...fujitsu.com>
>
> Only when a page is not found by page_index, we'll go to the error check.
>
> Signed-off-by: Liu Bo <liubo2009@...fujitsu.com>
> Signed-off-by: Miao Xie <miaox@...fujitsu.com>
> ---
>  fs/btrfs/compression.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index cb3877c..8458840 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -467,7 +467,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
>                rcu_read_lock();
>                page = radix_tree_lookup(&mapping->page_tree, page_index);
>                rcu_read_unlock();
> -               if (page) {
> +               if (!page) {
>  check_misses:
>                        misses++;
>                        if (misses > 4)

This patch is wrong. The word "miss" here means "miss for read-ahead because
the page is already in the page cache"

Yan, Zheng
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