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Message-Id: <20170126115819.58875-7-kirill.shutemov@linux.intel.com> Date: Thu, 26 Jan 2017 14:57:48 +0300 From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> To: "Theodore Ts'o" <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Jan Kara <jack@...e.com>, Andrew Morton <akpm@...ux-foundation.org> Cc: Alexander Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Dave Hansen <dave.hansen@...el.com>, Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>, Ross Zwisler <ross.zwisler@...ux.intel.com>, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-block@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: [PATCHv6 06/37] thp: handle write-protection faults for file THP For filesystems that wants to be write-notified (has mkwrite), we will encount write-protection faults for huge PMDs in shared mappings. The easiest way to handle them is to clear the PMD and let it refault as wriable. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> Reviewed-by: Jan Kara <jack@...e.cz> --- mm/memory.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 6bf2b471e30c..903d9d3e01c0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3488,8 +3488,16 @@ static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd) return vmf->vma->vm_ops->pmd_fault(vmf->vma, vmf->address, vmf->pmd, vmf->flags); + if (vmf->vma->vm_flags & VM_SHARED) { + /* Clear PMD */ + zap_page_range_single(vmf->vma, vmf->address & HPAGE_PMD_MASK, + HPAGE_PMD_SIZE, NULL); + + /* Refault to establish writable PMD */ + return 0; + } + /* COW handled on pte level: split pmd */ - VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma); __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL); return VM_FAULT_FALLBACK; -- 2.11.0
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