Messages in this thread Patch in this message | | | From | Ross Zwisler <> | Subject | [PATCH 1/2] mm: avoid spurious 'bad pmd' warning messages | Date | Wed, 17 May 2017 11:16:38 -0600 |
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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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