From: Dave Hansen <dave.hansen@intel.com>
To: Ross Zwisler <ross.zwisler@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-nvdimm@lists.01.org,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Pawel Lebioda <pawel.lebioda@intel.com>,
Dave Jiang <dave.jiang@intel.com>, Xiong Zhou <xzhou@redhat.com>,
Eryu Guan <eguan@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages
Date: Wed, 17 May 2017 10:33:58 -0700 [thread overview]
Message-ID: <9c45c769-2f5e-9327-c39e-1df7744fa633@intel.com> (raw)
In-Reply-To: <20170517171639.14501-1-ross.zwisler@linux.intel.com>
On 05/17/2017 10:16 AM, Ross Zwisler wrote:
> @@ -3061,7 +3061,7 @@ static int pte_alloc_one_map(struct vm_fault *vmf)
> * through an atomic read in C, which is what pmd_trans_unstable()
> * provides.
> */
> - if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd))
> + if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd))
> return VM_FAULT_NOPAGE;
I'm worried we are very unlikely to get this right in the future. It's
totally not obvious what the ordering requirement is here.
Could we move pmd_devmap() and pmd_trans_unstable() into a helper that
gets the ordering right and also spells out the ordering requirement?
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next prev parent reply other threads:[~2017-05-17 17:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-17 17:16 [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages Ross Zwisler
2017-05-17 17:16 ` [PATCH 2/2] dax: Fix race between colliding PMD & PTE entries Ross Zwisler
2017-05-17 17:17 ` [PATCH] generic: add regression test for DAX PTE/PMD races Ross Zwisler
2017-05-18 7:50 ` [PATCH 2/2] dax: Fix race between colliding PMD & PTE entries Jan Kara
2017-05-18 21:29 ` Ross Zwisler
2017-05-22 14:37 ` Jan Kara
2017-05-22 19:44 ` Ross Zwisler
2017-05-22 14:44 ` Jan Kara
2017-05-22 19:43 ` Ross Zwisler
2017-05-17 17:33 ` Dave Hansen [this message]
2017-05-17 18:23 ` [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages Ross Zwisler
2017-05-22 14:40 ` Jan Kara
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