[PATCH v3] mm: pmd dirty emulation in page fault handler
Minchan Kim
minchan at kernel.org
Thu Dec 22 23:53:07 PST 2016
Andreas reported [1] made a test in jemalloc hang in THP mode in arm64.
http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de
The problem is page fault handler supports only accessed flag emulation
for THP page of SW-dirty/accessed architecture.
This patch enables dirty-bit emulation for those architectures.
Without it, MADV_FREE makes application hang by repeated fault forever.
[1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called
Cc: Jason Evans <je at fb.com>
Cc: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: linux-arch at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: <stable at vger.kernel.org> [4.5+]
Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Reported-and-Tested-by: Andreas Schwab <schwab at suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
Signed-off-by: Minchan Kim <minchan at kernel.org>
---
* from v2
* Add acked-by/tested-by
* from v1
* Remove __handle_mm_fault part - Kirill
mm/huge_memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 10eedbf..29ec8a4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
{
pmd_t entry;
unsigned long haddr;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
goto unlock;
entry = pmd_mkyoung(orig_pmd);
+ if (write)
+ entry = pmd_mkdirty(entry);
haddr = vmf->address & HPAGE_PMD_MASK;
- if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
- vmf->flags & FAULT_FLAG_WRITE))
+ if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
unlock:
--
2.7.4
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