Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. http://lkml.kernel.org/r/[email protected]
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 <[email protected]> Cc: Kirill A. Shutemov <[email protected]> Cc: Will Deacon <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: [email protected] Cc: [email protected] Cc: <[email protected]> [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 <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Signed-off-by: Minchan Kim <[email protected]> --- * 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
