From: Roman Gushchin <guro@fb.com>
To: Matthew Wilcox <willy@infradead.org>
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 11:42:42 -0700 [thread overview]
Message-ID: <YPXHokLyedlmdrZ8@carbon.lan> (raw)
In-Reply-To: <YPXAxo6YzR8Mx/Bm@casper.infradead.org>
On Mon, Jul 19, 2021 at 07:13:26PM +0100, Matthew Wilcox wrote:
> 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.
Indeed! A good note.
>
> Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
>
Thank you!
prev parent reply other threads:[~2021-07-19 22:23 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
2021-07-19 18:42 ` Roman Gushchin [this message]
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