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authorAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>2019-05-13 17:19:11 -0700
committerPaul Gortmaker <paul.gortmaker@windriver.com>2019-09-16 12:20:37 -0400
commit6c961ac781501f5c2f775f60062608d322fe2a7d (patch)
tree761d5b95de998a6bc07e6d710aa9208e2add9069 /fs
parentfd1c77db4166de46d1752b330dd3413c40afbacb (diff)
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mm: page_mkclean vs MADV_DONTNEED race
commit 024eee0e83f0df52317be607ca521e0fc572aa07 upstream. MADV_DONTNEED is handled with mmap_sem taken in read mode. We call page_mkclean without holding mmap_sem. MADV_DONTNEED implies that pages in the region are unmapped and subsequent access to the pages in that range is handled as a new page fault. This implies that if we don't have parallel access to the region when MADV_DONTNEED is run we expect those range to be unallocated. w.r.t page_mkclean() we need to make sure that we don't break the MADV_DONTNEED semantics. MADV_DONTNEED check for pmd_none without holding pmd_lock. This implies we skip the pmd if we temporarily mark pmd none. Avoid doing that while marking the page clean. Keep the sequence same for dax too even though we don't support MADV_DONTNEED for dax mapping The bug was noticed by code review and I didn't observe any failures w.r.t test run. This is similar to commit 58ceeb6bec86d9140f9d91d71a710e963523d063 Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Date: Thu Apr 13 14:56:26 2017 -0700 thp: fix MADV_DONTNEED vs. MADV_FREE race commit ced108037c2aa542b3ed8b7afd1576064ad1362a Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Date: Thu Apr 13 14:56:20 2017 -0700 thp: fix MADV_DONTNEED vs. numa balancing race Link: http://lkml.kernel.org/r/20190321040610.14226-1-aneesh.kumar@linux.ibm.com Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc:"Kirill A . Shutemov" <kirill@shutemov.name> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/dax.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 0d3f640653c0..b2ade8141183 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -795,7 +795,7 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
goto unlock_pmd;
flush_cache_page(vma, address, pfn);
- pmd = pmdp_huge_clear_flush(vma, address, pmdp);
+ pmd = pmdp_invalidate(vma, address, pmdp);
pmd = pmd_wrprotect(pmd);
pmd = pmd_mkclean(pmd);
set_pmd_at(vma->vm_mm, address, pmdp, pmd);