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authorRoss Zwisler <ross.zwisler@linux.intel.com>2017-01-10 16:57:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-10 18:31:54 -0800
commitf729c8c9b24f0540a6e6b86e68f3888ba90ef7e7 (patch)
tree8dd956224ce2b958954c5bfe0b7cf1809299dce6 /fs
parent097963959594c5eccaba42510f7033f703211bda (diff)
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dax: wrprotect pmd_t in dax_mapping_entry_mkclean
Currently dax_mapping_entry_mkclean() fails to clean and write protect the pmd_t of a DAX PMD entry during an *sync operation. This can result in data loss in the following sequence: 1) mmap write to DAX PMD, dirtying PMD radix tree entry and making the pmd_t dirty and writeable 2) fsync, flushing out PMD data and cleaning the radix tree entry. We currently fail to mark the pmd_t as clean and write protected. 3) more mmap writes to the PMD. These don't cause any page faults since the pmd_t is dirty and writeable. The radix tree entry remains clean. 4) fsync, which fails to flush the dirty PMD data because the radix tree entry was clean. 5) crash - dirty data that should have been fsync'd as part of 4) could still have been in the processor cache, and is lost. Fix this by marking the pmd_t clean and write protected in dax_mapping_entry_mkclean(), which is called as part of the fsync operation 2). This will cause the writes in step 3) above to generate page faults where we'll re-dirty the PMD radix tree entry, resulting in flushes in the fsync that happens in step 4). Fixes: 4b4bb46d00b3 ("dax: clear dirty entry tags on cache flush") Link: http://lkml.kernel.org/r/1482272586-21177-3-git-send-email-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/dax.c51
1 files changed, 36 insertions, 15 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 5c74f60d0a50..ddcddfeaa03b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -691,8 +691,8 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
pgoff_t index, unsigned long pfn)
{
struct vm_area_struct *vma;
- pte_t *ptep;
- pte_t pte;
+ pte_t pte, *ptep = NULL;
+ pmd_t *pmdp = NULL;
spinlock_t *ptl;
bool changed;
@@ -707,21 +707,42 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
address = pgoff_address(index, vma);
changed = false;
- if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
+ if (follow_pte_pmd(vma->vm_mm, address, &ptep, &pmdp, &ptl))
continue;
- if (pfn != pte_pfn(*ptep))
- goto unlock;
- if (!pte_dirty(*ptep) && !pte_write(*ptep))
- goto unlock;
- flush_cache_page(vma, address, pfn);
- pte = ptep_clear_flush(vma, address, ptep);
- pte = pte_wrprotect(pte);
- pte = pte_mkclean(pte);
- set_pte_at(vma->vm_mm, address, ptep, pte);
- changed = true;
-unlock:
- pte_unmap_unlock(ptep, ptl);
+ if (pmdp) {
+#ifdef CONFIG_FS_DAX_PMD
+ pmd_t pmd;
+
+ if (pfn != pmd_pfn(*pmdp))
+ goto unlock_pmd;
+ if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
+ goto unlock_pmd;
+
+ flush_cache_page(vma, address, pfn);
+ pmd = pmdp_huge_clear_flush(vma, address, pmdp);
+ pmd = pmd_wrprotect(pmd);
+ pmd = pmd_mkclean(pmd);
+ set_pmd_at(vma->vm_mm, address, pmdp, pmd);
+ changed = true;
+unlock_pmd:
+ spin_unlock(ptl);
+#endif
+ } else {
+ if (pfn != pte_pfn(*ptep))
+ goto unlock_pte;
+ if (!pte_dirty(*ptep) && !pte_write(*ptep))
+ goto unlock_pte;
+
+ flush_cache_page(vma, address, pfn);
+ pte = ptep_clear_flush(vma, address, ptep);
+ pte = pte_wrprotect(pte);
+ pte = pte_mkclean(pte);
+ set_pte_at(vma->vm_mm, address, ptep, pte);
+ changed = true;
+unlock_pte:
+ pte_unmap_unlock(ptep, ptl);
+ }
if (changed)
mmu_notifier_invalidate_page(vma->vm_mm, address);