From: Matthew Wilcox <willy@infradead.org>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Jan Kara <jack@suse.cz>, Dave Chinner <dchinner@redhat.com>,
Murphy Zhou <jencce.kernel@gmail.com>,
"Darrick J . Wong" <djwong@kernel.org>
Subject: Re: [PATCH] writeback, cgroup: do not reparent dax inodes
Date: Mon, 19 Jul 2021 19:13:26 +0100 [thread overview]
Message-ID: <YPXAxo6YzR8Mx/Bm@casper.infradead.org> (raw)
In-Reply-To: <20210719171350.3876830-1-guro@fb.com>
On Mon, Jul 19, 2021 at 10:13:50AM -0700, Roman Gushchin wrote:
> The inode switching code is not suited for dax inodes. An attempt
> to switch a dax inode to a parent writeback structure (as a part
> of a writeback cleanup procedure) results in a panic like this:
[...]
> The crash happens on an attempt to iterate over attached pagecache
> pages and check the dirty flag: a dax inode's xarray contains pfn's
> instead of generic struct page pointers.
I wondered why this happens for DAX and not for other kinds of non-page
entries in the inodes. The answer is that it's a tagged iteration, and
shadow/swap entries are never tagged; only DAX entries get tagged.
Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
next prev parent reply other threads:[~2021-07-19 18:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 17:13 [PATCH] writeback, cgroup: do not reparent dax inodes Roman Gushchin
2021-07-19 18:04 ` Darrick J. Wong
2021-07-19 18:42 ` Roman Gushchin
2021-07-19 18:13 ` Matthew Wilcox [this message]
2021-07-19 18:42 ` Roman Gushchin
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