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From: Joseph Qi <joseph.qi@linux.alibaba.com>
To: Jan Kara <jack@suse.cz>
Cc: ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] Possible fs corruption when hole punch races with other ops
Date: Thu, 22 Apr 2021 11:22:07 +0800	[thread overview]
Message-ID: <c4d119be-e263-366c-c2c2-6c58ee852977@linux.alibaba.com> (raw)
In-Reply-To: <20210421162953.GA13863@quack2.suse.cz>

Hi,

Checked the code flow, it seems the race you worried truly exists.
We have to take ip_alloc_sem before calling into ocfs2_get_block().

Thanks,
Joseph

On 4/22/21 12:29 AM, Jan Kara wrote:
> Hello,
> 
> I'm unifying protection various filesystems use to protect hole punch
> operations from racing with other operations (like readahead, page fault,
> writepage etc.). I was looking into OCFS2 and I think it is prone to a
> following race which can possibly lead to filesystem corruption. But maybe
> I miss something so that's why I'm writing here. The scenario I'm concerned
> about is:
> 
> CPU1					CPU2
> ocfs2_remove_inode_range()		ocfs2_writepage()
>   ...					  block_write_full_page()
>   ocfs2_remove_btree_range()		    ocfs2_extent_map_get_blocks()
> 
> Now ocfs2_extent_map_get_blocks() runs without protection of ip_alloc_sem
> AFAICT and so both these operations can be modifying extent map at the same
> time? What am I missing?
> 
> 								Honza
> 

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  reply	other threads:[~2021-04-22  3:25 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21 16:29 [Ocfs2-devel] Possible fs corruption when hole punch races with other ops Jan Kara
2021-04-22  3:22 ` Joseph Qi [this message]
2021-04-22 10:44   ` Jan Kara
2021-04-22 15:56     ` Wengang Wang
2021-04-22 16:06       ` Darrick J. Wong
2021-04-22 16:36         ` Wengang Wang
2021-04-22 16:46           ` Darrick J. Wong

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