From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, darrick.wong@oracle.com,
linux-xfs <linux-xfs@vger.kernel.org>,
Ross Zwisler <zwisler@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
lczerner@redhat.com, linux-ext4 <linux-ext4@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v4 0/2] ext4: fix DAX dma vs truncate/hole-punch
Date: Mon, 6 Aug 2018 17:49:43 +0200 [thread overview]
Message-ID: <20180806154943.GA17666@lst.de> (raw)
In-Reply-To: <20180806035550.GE7395@dastard>
> > > This allows the direct I/O path to do I/O and raise & lower page->_refcount
> > > while we're executing a truncate/hole punch. This leads to us trying to free
> > > a page with an elevated refcount.
>
> I don't see how this is possible in XFS - maybe I'm missing
> something, but "direct IO submission during truncate" is not
> something that should ever be happening in XFS, DAX or not.
The pages involved in a direct I/O are not that of the file that
the direct I/O read/write syscalls are called on, but those of the
memory regions the direct I/O read/write syscalls operate on.
Those pages could be file backed and undergo a truncate at the
same time.
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Linux-nvdimm@lists.01.org
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <zwisler@kernel.org>, Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, darrick.wong@oracle.com,
lczerner@redhat.com, linux-ext4 <linux-ext4@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH v4 0/2] ext4: fix DAX dma vs truncate/hole-punch
Date: Mon, 6 Aug 2018 17:49:43 +0200 [thread overview]
Message-ID: <20180806154943.GA17666@lst.de> (raw)
In-Reply-To: <20180806035550.GE7395@dastard>
> > > This allows the direct I/O path to do I/O and raise & lower page->_refcount
> > > while we're executing a truncate/hole punch. This leads to us trying to free
> > > a page with an elevated refcount.
>
> I don't see how this is possible in XFS - maybe I'm missing
> something, but "direct IO submission during truncate" is not
> something that should ever be happening in XFS, DAX or not.
The pages involved in a direct I/O are not that of the file that
the direct I/O read/write syscalls are called on, but those of the
memory regions the direct I/O read/write syscalls operate on.
Those pages could be file backed and undergo a truncate at the
same time.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
To: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org,
linux-xfs <linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Ross Zwisler <zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-fsdevel
<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
lczerner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
linux-ext4 <linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH v4 0/2] ext4: fix DAX dma vs truncate/hole-punch
Date: Mon, 6 Aug 2018 17:49:43 +0200 [thread overview]
Message-ID: <20180806154943.GA17666@lst.de> (raw)
In-Reply-To: <20180806035550.GE7395@dastard>
> > > This allows the direct I/O path to do I/O and raise & lower page->_refcount
> > > while we're executing a truncate/hole punch. This leads to us trying to free
> > > a page with an elevated refcount.
>
> I don't see how this is possible in XFS - maybe I'm missing
> something, but "direct IO submission during truncate" is not
> something that should ever be happening in XFS, DAX or not.
The pages involved in a direct I/O are not that of the file that
the direct I/O read/write syscalls are called on, but those of the
memory regions the direct I/O read/write syscalls operate on.
Those pages could be file backed and undergo a truncate at the
same time.
next prev parent reply other threads:[~2018-08-06 15:44 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 19:10 [PATCH v4 0/2] ext4: fix DAX dma vs truncate/hole-punch Ross Zwisler
2018-07-10 19:10 ` Ross Zwisler
2018-07-10 19:10 ` [PATCH v4 1/2] dax: dax_layout_busy_page() warn on !exceptional Ross Zwisler
2018-07-10 19:10 ` Ross Zwisler
2018-08-10 19:52 ` Eric Sandeen
2018-08-10 19:52 ` Eric Sandeen
2018-08-10 20:33 ` Theodore Y. Ts'o
2018-08-10 20:33 ` Theodore Y. Ts'o
2018-08-11 2:10 ` Theodore Y. Ts'o
2018-08-11 2:10 ` Theodore Y. Ts'o
2018-08-13 10:12 ` Jan Kara
2018-08-13 10:12 ` Jan Kara
2018-08-13 12:46 ` Theodore Y. Ts'o
2018-08-13 12:46 ` Theodore Y. Ts'o
2018-08-24 15:44 ` Jan Kara
2018-08-24 15:44 ` Jan Kara
2018-08-27 16:09 ` Jan Kara
2018-08-27 16:09 ` Jan Kara
2018-07-10 19:10 ` [PATCH v4 2/2] ext4: handle layout changes to pinned DAX mappings Ross Zwisler
2018-07-10 19:10 ` Ross Zwisler
2018-07-11 8:17 ` [PATCH v4 0/2] ext4: fix DAX dma vs truncate/hole-punch Jan Kara
2018-07-11 8:17 ` Jan Kara
2018-07-11 15:41 ` Ross Zwisler
2018-07-11 15:41 ` Ross Zwisler
2018-07-25 22:28 ` Ross Zwisler
2018-07-25 22:28 ` Ross Zwisler
2018-07-27 16:28 ` Ross Zwisler
2018-07-27 16:28 ` Ross Zwisler
2018-07-27 16:28 ` Ross Zwisler
2018-08-06 3:55 ` Dave Chinner
2018-08-06 3:55 ` Dave Chinner
2018-08-06 3:55 ` Dave Chinner
2018-08-06 15:49 ` Christoph Hellwig [this message]
2018-08-06 15:49 ` Christoph Hellwig
2018-08-06 15:49 ` Christoph Hellwig
2018-08-06 22:25 ` Dave Chinner
2018-08-06 22:25 ` Dave Chinner
2018-08-06 22:25 ` Dave Chinner
2018-08-07 8:45 ` Jan Kara
2018-08-07 8:45 ` Jan Kara
2018-08-07 8:45 ` Jan Kara
2018-09-10 22:18 ` Eric Sandeen
2018-09-10 22:18 ` Eric Sandeen
2018-09-10 22:18 ` Eric Sandeen
2018-09-11 15:14 ` Jan Kara
2018-09-11 15:14 ` Jan Kara
2018-09-11 15:14 ` Jan Kara
2018-09-11 15:20 ` Jan Kara
2018-09-11 15:20 ` Jan Kara
2018-09-11 15:20 ` Jan Kara
2018-09-11 17:28 ` Theodore Y. Ts'o
2018-09-11 17:28 ` Theodore Y. Ts'o
2018-09-11 17:28 ` Theodore Y. Ts'o
2018-09-11 18:21 ` Eric Sandeen
2018-09-11 18:21 ` Eric Sandeen
2018-09-11 18:21 ` Eric Sandeen
2018-07-31 19:44 ` Ross Zwisler
2018-07-31 19:44 ` Ross Zwisler
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