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Message-ID: <20230710154803.00004047.zbestahu@gmail.com>
Date: Mon, 10 Jul 2023 15:48:03 +0800
From: Yue Hu <zbestahu@...il.com>
To: Chunhai Guo <guochunhai@...o.com>
Cc: xiang@...nel.org, chao@...nel.org, linux-erofs@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, huyue2@...lpad.com
Subject: Re: [PATCH] erofs: avoid unnecessary loops in
z_erofs_pcluster_readmore() when read page beyond EOF
On Mon, 10 Jul 2023 12:25:31 +0800
Chunhai Guo <guochunhai@...o.com> wrote:
> z_erofs_pcluster_readmore() may take a long time to loop when the page
> offset is large enough, which is unnecessary should be prevented.
> For example, when the following case is encountered, it will loop 4691368
> times, taking about 27 seconds.
> - offset = 19217289215
> - inode_size = 1442672
>
> Signed-off-by: Chunhai Guo <guochunhai@...o.com>
> ---
> fs/erofs/zdata.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 5f1890e309c6..d9a0763f4595 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -1841,7 +1841,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
> }
>
> cur = map->m_la + map->m_llen - 1;
> - while (cur >= end) {
> + while ((cur >= end) && (cur < i_size_read(inode))) {
> pgoff_t index = cur >> PAGE_SHIFT;
> struct page *page;
>
Reviewed-by: Yue Hu <huyue2@...lpad.com>
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