From: Jan Kara <jack@suse.cz>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>,
linux-fsdevel@vger.kernel.org,
Matthew Wilcox <willy@infradead.org>,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH 0/3 RFC] fs: Hole punch vs page cache filling races
Date: Tue, 6 Apr 2021 14:17:02 +0200 [thread overview]
Message-ID: <20210406121702.GB19407@quack2.suse.cz> (raw)
In-Reply-To: <YGdxtbun4bT/Mko4@mit.edu>
On Fri 02-04-21 15:34:13, Theodore Ts'o wrote:
> On Wed, Jan 20, 2021 at 05:06:08PM +0100, Jan Kara wrote:
> >
> > Amir has reported [1] a that ext4 has a potential issues when reads can race
> > with hole punching possibly exposing stale data from freed blocks or even
> > corrupting filesystem when stale mapping data gets used for writeout. The
> > problem is that during hole punching, new page cache pages can get instantiated
> > in a punched range after truncate_inode_pages() has run but before the
> > filesystem removes blocks from the file. In principle any filesystem
> > implementing hole punching thus needs to implement a mechanism to block
> > instantiating page cache pages during hole punching to avoid this race. This is
> > further complicated by the fact that there are multiple places that can
> > instantiate pages in page cache. We can have regular read(2) or page fault
> > doing this but fadvise(2) or madvise(2) can also result in reading in page
> > cache pages through force_page_cache_readahead().
>
> What's the current status of this patch set? I'm going through
> pending patches and it looks like folks don't like Jan's proposed
> solution. What are next steps?
Note that I did post v2 here:
https://lore.kernel.org/linux-fsdevel/20210208163918.7871-1-jack@suse.cz/
It didn't get much comments though. I guess I'll rebase the series, include
the explanations I've added in my reply to Dave and resend.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2021-04-06 12:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 16:06 [PATCH 0/3 RFC] fs: Hole punch vs page cache filling races Jan Kara
2021-01-20 16:06 ` [PATCH 1/3] mm: Do not pass iter into generic_file_buffered_read_get_pages() Jan Kara
2021-01-20 16:18 ` Christoph Hellwig
2021-01-20 16:06 ` [PATCH 2/3] mm: Provide address_space operation for filling pages for read Jan Kara
2021-01-20 16:20 ` Christoph Hellwig
2021-01-20 17:27 ` Jan Kara
2021-01-20 17:28 ` Christoph Hellwig
2021-01-20 17:56 ` Matthew Wilcox
2021-04-02 21:17 ` Kent Overstreet
2021-04-06 12:21 ` Jan Kara
2021-01-20 16:06 ` [PATCH 3/3] ext4: Fix stale data exposure when read races with hole punch Jan Kara
2021-01-21 19:27 ` [PATCH 0/3 RFC] fs: Hole punch vs page cache filling races Matthew Wilcox
2021-01-22 14:32 ` Jan Kara
2021-04-02 19:34 ` Theodore Ts'o
2021-04-06 12:17 ` Jan Kara [this message]
2021-04-06 16:45 ` Theodore Ts'o
2021-04-06 16:50 ` Theodore Ts'o
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