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dax: ensure that zero pages are removed from other processes
If the first access to a huge page was a store, there would be no existing zero pmd in this process's page tables. There could be a zero pmd in another process's page tables, if it had done a load. We can detect this case by noticing that the buffer_head returned from the filesystem is New, and ensure that other processes mapping this huge page have their page tables flushed. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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6
fs/dax.c
6
fs/dax.c
@ -568,7 +568,11 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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if ((pgoff | PG_PMD_COLOUR) >= size)
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goto fallback;
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if (is_huge_zero_pmd(*pmd))
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/*
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* If we allocated new storage, make sure no process has any
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* zero pages covering this hole
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*/
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if (buffer_new(&bh))
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unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
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if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
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