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authorRoss Zwisler <ross.zwisler@linux.intel.com>2016-01-15 16:56:02 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-15 17:56:32 -0800
commit01871e59af5cc1cbf290ad6b4b95cd2f0cec9e8c (patch)
tree8c12bb4cd4be99b3e4f4d06e34bd9f1eb3c6aefa
parentb2e0d1625e193b40cbbd45b799f82d54d34e015c (diff)
mm, dax: fix livelock, allow dax pmd mappings to become writeable
Prior to this change DAX PMD mappings that were made read-only were never able to be made writable again. This is because the code in insert_pfn_pmd() that calls pmd_mkdirty() and pmd_mkwrite() would skip these calls if the PMD already existed in the page table. Instead, if we are doing a write always mark the PMD entry as dirty and writeable. Without this code we can get into a condition where we mark the PMD as read-only, and then on a subsequent write fault we get into an infinite loop of PMD faults where we try unsuccessfully to make the PMD writeable. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reported-by: Jeff Moyer <jmoyer@redhat.com> Reported-by: Toshi Kani <toshi.kani@hpe.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/huge_memory.c14
1 files changed, 6 insertions, 8 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9d12d63a0ddd..996e86dbeb43 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -938,15 +938,13 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
spinlock_t *ptl;
ptl = pmd_lock(mm, pmd);
- if (pmd_none(*pmd)) {
- entry = pmd_mkhuge(pfn_pmd(pfn, prot));
- if (write) {
- entry = pmd_mkyoung(pmd_mkdirty(entry));
- entry = maybe_pmd_mkwrite(entry, vma);
- }
- set_pmd_at(mm, addr, pmd, entry);
- update_mmu_cache_pmd(vma, addr, pmd);
+ entry = pmd_mkhuge(pfn_pmd(pfn, prot));
+ if (write) {
+ entry = pmd_mkyoung(pmd_mkdirty(entry));
+ entry = maybe_pmd_mkwrite(entry, vma);
}
+ set_pmd_at(mm, addr, pmd, entry);
+ update_mmu_cache_pmd(vma, addr, pmd);
spin_unlock(ptl);
}