From: Ross Zwisler <zwisler@gmail.com>
To: Matthew Wilcox <willy@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
linux-nvdimm <linux-nvdimm@ml01.01.org>,
Dave Chinner <david@fromorbit.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 2/2] dax: fix bdev NULL pointer dereferences
Date: Sat, 30 Jan 2016 23:12:12 -0700 [thread overview]
Message-ID: <33D2FA63-0EBC-4E5F-B337-F06A8A846166@gmail.com> (raw)
In-Reply-To: <20160131023247.GZ2948@linux.intel.com>
> On Jan 30, 2016, at 7:32 PM, Matthew Wilcox <willy@linux.intel.com> wrote:
>
>> On Fri, Jan 29, 2016 at 10:01:13PM -0800, Dan Williams wrote:
>>> On Fri, Jan 29, 2016 at 9:28 PM, Matthew Wilcox <willy@linux.intel.com> wrote:
>>> If we store the PFN of the underlying page instead, we don't have this
>>> problem. Instead, we have a different problem; of the device going
>>> away under us. I'm trying to find the code which tears down PTEs when
>>> the device goes away, and I'm not seeing it. What do we do about user
>>> mappings of the device?
>>
>> I deferred the dax tear down code until next cycle as Al rightly
>> pointed out some needed re-works:
>>
>> https://lists.01.org/pipermail/linux-nvdimm/2016-January/003995.html
>
> Thanks; I eventually found it in my email somewhere over the Pacific.
>
> I did probably 70% of the work needed to switch the radix tree over to
> storing PFNs instead of sectors. It seems viable, though it's a big
> change from where we are today:
At one point I had kaddrs in the radix tree, so I could just pull the addresses out
and flush them. That would save us a pfn -> kaddrs conversion before flush.
Is there a reason to store pnfs instead of kaddrs in the radix tree?
>
> fs/dax.c | 415 +++++++++++++++++++++++----------------------
> include/linux/dax.h | 3 +-
> include/linux/pfn_t.h | 33 +++-
> include/linux/radix-tree.h | 9 -
> 4 files changed, 236 insertions(+), 224 deletions(-)
>
> I'll try and get that finished off this week.
>
> One concrete and easily-separable piece is that dax_clear_blocks() has
> the wrong signature. It currently takes an inode & block as parameters;
> it has no way of finding out the correct block device. It's only two
> callers are filesystems (ext2 and xfs). Those filesystems should be
> passing the block_device instead of the inode. But without the inode,
> we can't convert a block number to a sector number, so we also need
> to pass the sector number, not the block number. It still has type
> sector_t, annoyingly.
>
> @@ -63,12 +238,11 @@ static void dax_unmap_atomic(struct block_device *bdev,
> * and hence this means the stack from this point must follow GFP_NOFS
> * semantics for all operations.
> */
> -int dax_clear_blocks(struct inode *inode, sector_t block, long _size)
> +int dax_clear_blocks(struct block_device *bdev, sector_t sector, long size)
> {
> - struct block_device *bdev = inode->i_sb->s_bdev;
> struct blk_dax_ctl dax = {
> - .sector = block << (inode->i_blkbits - 9),
> - .size = _size,
> + .sector = sector,
> + .size = size,
> };
>
> might_sleep();
>
> but I haven't looked at doing the conversion of xfs or ext2 to use that
> new interface.
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@lists.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm
next prev parent reply other threads:[~2016-01-31 6:12 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 19:35 [PATCH 1/2] block: fix pfn_mkwrite() DAX fault handler Ross Zwisler
2016-01-28 19:35 ` [PATCH 2/2] dax: fix bdev NULL pointer dereferences Ross Zwisler
2016-01-28 20:21 ` Dan Williams
2016-01-28 21:38 ` Christoph Hellwig
2016-01-29 18:28 ` Ross Zwisler
2016-01-29 23:34 ` Ross Zwisler
2016-01-30 0:18 ` Dan Williams
2016-01-31 22:44 ` Dave Chinner
2016-01-30 5:28 ` Matthew Wilcox
2016-01-30 6:01 ` Dan Williams
2016-01-30 7:08 ` Jared Hulbert
2016-01-31 2:32 ` Matthew Wilcox
2016-01-31 6:12 ` Ross Zwisler [this message]
2016-01-31 10:55 ` Matthew Wilcox
2016-01-31 16:38 ` Dan Williams
2016-01-31 18:07 ` Matthew Wilcox
2016-01-31 18:18 ` Dan Williams
2016-01-31 18:27 ` Matthew Wilcox
2016-01-31 18:50 ` Dan Williams
2016-01-31 19:51 ` Dan Williams
2016-02-01 13:44 ` Matthew Wilcox
2016-02-01 14:51 ` Jan Kara
2016-02-01 20:49 ` Matthew Wilcox
2016-02-01 21:47 ` Dave Chinner
2016-02-02 6:06 ` Jared Hulbert
2016-02-02 6:46 ` Dan Williams
2016-02-02 8:05 ` Jared Hulbert
2016-02-02 16:51 ` Dan Williams
2016-02-02 21:46 ` Jared Hulbert
2016-02-03 0:34 ` Matthew Wilcox
2016-02-03 1:21 ` Jared Hulbert
2016-02-02 11:17 ` Jan Kara
2016-02-02 16:33 ` Dan Williams
2016-02-02 16:46 ` Jan Kara
2016-02-02 17:10 ` Dan Williams
2016-02-02 17:34 ` Ross Zwisler
2016-02-02 17:46 ` Dan Williams
2016-02-02 17:47 ` Dan Williams
2016-02-02 18:24 ` Ross Zwisler
2016-02-02 18:46 ` Matthew Wilcox
2016-02-02 18:59 ` Dan Williams
2016-02-02 20:14 ` Matthew Wilcox
2016-02-03 11:09 ` Jan Kara
2016-02-03 10:46 ` Jan Kara
2016-02-03 20:13 ` Ross Zwisler
2016-02-04 9:15 ` Jan Kara
2016-02-04 23:38 ` Ross Zwisler
2016-02-06 23:15 ` Dave Chinner
2016-02-07 5:27 ` Ross Zwisler
2016-02-04 19:56 ` Ross Zwisler
2016-02-04 20:29 ` Jan Kara
2016-02-04 22:19 ` Ross Zwisler
2016-02-05 22:25 ` Ross Zwisler
2016-02-06 23:40 ` Dave Chinner
2016-02-07 6:43 ` Ross Zwisler
2016-02-08 13:48 ` Jan Kara
2016-02-07 8:38 ` Christoph Hellwig
2016-02-08 15:55 ` Ross Zwisler
2016-02-02 18:41 ` Ross Zwisler
2016-02-02 18:53 ` Ross Zwisler
2016-02-02 0:02 ` Ross Zwisler
2016-02-02 7:10 ` Dave Chinner
2016-02-02 10:34 ` Jan Kara
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