From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
"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>,
Dave Hansen <dave.hansen@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: [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages
Date: Wed, 17 May 2017 11:16:38 -0600 [thread overview]
Message-ID: <20170517171639.14501-1-ross.zwisler@linux.intel.com> (raw)
When the pmd_devmap() checks were added by:
commit 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd")
to add better support for DAX huge pages, they were all added to the end of
if() statements after existing pmd_trans_huge() checks. So, things like:
- if (pmd_trans_huge(*pmd))
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))
When further checks were added after pmd_trans_unstable() checks by:
commit 7267ec008b5c ("mm: postpone page table allocation until we have page
to map")
they were also added at the end of the conditional:
+ if (pmd_trans_unstable(fe->pmd) || pmd_devmap(*fe->pmd))
This ordering is fine for pmd_trans_huge(), but doesn't work for
pmd_trans_unstable(). This is because DAX huge pages trip the bad_pmd()
check inside of pmd_none_or_trans_huge_or_clear_bad() (called by
pmd_trans_unstable()), which prints out a warning and returns 1. So, we do
end up doing the right thing, but only after spamming dmesg with suspicious
looking messages:
mm/pgtable-generic.c:39: bad pmd ffff8808daa49b88(84000001006000a5)
Reorder these checks so that pmd_devmap() is checked first, avoiding the
error messages.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Fixes: commit 7267ec008b5c ("mm: postpone page table allocation until we have page to map")
Cc: stable@vger.kernel.org
---
mm/memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 6ff5d72..1ee269d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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;
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
@@ -3690,7 +3690,7 @@ static int handle_pte_fault(struct vm_fault *vmf)
vmf->pte = NULL;
} else {
/* See comment in pte_alloc_one_map() */
- if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd))
+ if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd))
return 0;
/*
* A regular pmd is established and it can't morph into a huge
--
2.9.4
--
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next reply other threads:[~2017-05-17 17:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-17 17:16 Ross Zwisler [this message]
2017-05-17 17:16 ` [PATCH 2/2] dax: Fix race between colliding PMD & PTE entries Ross Zwisler
2017-05-18 7:50 ` 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 ` [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages Dave Hansen
2017-05-17 18:23 ` Ross Zwisler
2017-05-22 14:40 ` Jan Kara
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