From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: rdodgen@gmail.com
Cc: linux-ext4@vger.kernel.org, tytso@mit.edu,
Randy Dodgen <dodgen@google.com>,
linux-nvdimm@lists.01.org
Subject: Re: [PATCH v3] Fix ext4 fault handling when mounted with -o dax,ro
Date: Thu, 24 Aug 2017 09:11:38 -0600 [thread overview]
Message-ID: <20170824151138.GA25588@linux.intel.com> (raw)
In-Reply-To: <416a465a9fbe1d27085883dbf652c115cd195697.1503523424.git.dodgen@google.com>
On Wed, Aug 23, 2017 at 02:26:52PM -0700, rdodgen@gmail.com wrote:
> From: Randy Dodgen <dodgen@google.com>
>
> If an ext4 filesystem is mounted with both the DAX and read-only
> options, executables on that filesystem will fail to start (claiming
> 'Segmentation fault') due to the fault handler returning
> VM_FAULT_SIGBUS.
>
> This is due to the DAX fault handler (see ext4_dax_huge_fault)
> attempting to write to the journal when FAULT_FLAG_WRITE is set. This is
> the wrong behavior for write faults which will lead to a COW page; in
> particular, this fails for readonly mounts.
>
> This change avoids journal writes for faults that are expected to COW.
>
> It might be the case that this could be better handled in
> ext4_iomap_begin / ext4_iomap_end (called via iomap_ops inside
> dax_iomap_fault). These is some overlap already (e.g. grabbing journal
> handles).
>
> Signed-off-by: Randy Dodgen <dodgen@google.com>
Cool, looks good from the DAX point of view. You can add:
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
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next prev parent reply other threads:[~2017-08-24 15:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170822222434.146233-1-dodgen@google.com>
2017-08-23 3:37 ` [PATCH v2] Fix ext4 fault handling when mounted with -o dax,ro rdodgen
2017-08-23 16:38 ` Ross Zwisler
2017-08-23 20:11 ` Randy Dodgen
2017-08-23 21:26 ` [PATCH v3] " rdodgen
2017-08-24 14:45 ` Jan Kara
2017-08-24 15:11 ` Ross Zwisler [this message]
2017-08-24 16:01 ` Christoph Hellwig
2017-08-24 20:57 ` Theodore Ts'o
2017-08-25 7:28 ` Christoph Hellwig
2017-08-29 21:20 ` Christoph Hellwig
2017-08-29 21:37 ` Ross Zwisler
2017-08-29 22:07 ` Randy Dodgen
2017-08-29 22:37 ` [fstests PATCH] generic: add test for executables on read-only DAX mounts Ross Zwisler
2017-08-30 10:59 ` Eryu Guan
2017-08-31 4:01 ` Ross Zwisler
2017-08-31 4:09 ` [fstests v2] " Ross Zwisler
2017-08-30 14:51 ` [fstests PATCH] " Christoph Hellwig
2017-08-31 4:02 ` Ross Zwisler
2017-08-31 13:09 ` Christoph Hellwig
2017-08-24 19:26 ` [PATCH v3] Fix ext4 fault handling when mounted with -o dax,ro Theodore Ts'o
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