From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f182.google.com (mail-ig0-f182.google.com [209.85.213.182]) by kanga.kvack.org (Postfix) with ESMTP id 4F0AD6B0005 for ; Wed, 6 Apr 2016 10:06:41 -0400 (EDT) Received: by mail-ig0-f182.google.com with SMTP id kb1so41897039igb.0 for ; Wed, 06 Apr 2016 07:06:41 -0700 (PDT) Received: from g1t5425.austin.hp.com (g1t5425.austin.hp.com. [15.216.225.55]) by mx.google.com with ESMTPS id z79si3134165ioi.42.2016.04.06.07.06.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Apr 2016 07:06:40 -0700 (PDT) From: Toshi Kani Subject: [PATCH] x86 get_unmapped_area: Add PMD alignment for DAX PMD mmap Date: Wed, 6 Apr 2016 07:58:09 -0600 Message-Id: <1459951089-14911-1-git-send-email-toshi.kani@hpe.com> Sender: owner-linux-mm@kvack.org List-ID: To: mingo@kernel.org, bp@suse.de, hpa@zytor.com, tglx@linutronix.de Cc: dan.j.williams@intel.com, willy@linux.intel.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, x86@kernel.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, Toshi Kani When CONFIG_FS_DAX_PMD is set, DAX supports mmap() using PMD page size. This feature relies on both mmap virtual address and FS block data (i.e. physical address) to be aligned by the PMD page size. Users can use mkfs options to specify FS to align block allocations. However, aligning mmap() address requires application changes to mmap() calls, such as: - /* let the kernel to assign a mmap addr */ - mptr = mmap(NULL, fsize, PROT_READ|PROT_WRITE, FLAGS, fd, 0); + /* 1. obtain a PMD-aligned virtual address */ + ret = posix_memalign(&mptr, PMD_SIZE, fsize); + if (!ret) + free(mptr); /* 2. release the virt addr */ + + /* 3. then pass the PMD-aligned virt addr to mmap() */ + mptr = mmap(mptr, fsize, PROT_READ|PROT_WRITE, FLAGS, fd, 0); These changes add unnecessary dependency to DAX and PMD page size into application code. The kernel should assign a mmap address appropriate for the operation. Change arch_get_unmapped_area() and arch_get_unmapped_area_topdown() to request PMD_SIZE alignment when the request is for a DAX file and its mapping range is large enough for using a PMD page. Signed-off-by: Toshi Kani Cc: Thomas Gleixner Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Borislav Petkov Cc: Dan Williams Cc: Matthew Wilcox Cc: Kirill A. Shutemov --- arch/x86/kernel/sys_x86_64.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index 10e0272..a294c66 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -157,6 +157,13 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, info.align_mask = get_align_mask(); info.align_offset += get_align_bits(); } + if (filp && IS_ENABLED(CONFIG_FS_DAX_PMD) && IS_DAX(file_inode(filp))) { + unsigned long off_end = info.align_offset + len; + unsigned long off_pmd = round_up(info.align_offset, PMD_SIZE); + + if ((off_end > off_pmd) && ((off_end - off_pmd) >= PMD_SIZE)) + info.align_mask |= (PMD_SIZE - 1); + } return vm_unmapped_area(&info); } @@ -200,6 +207,13 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, info.align_mask = get_align_mask(); info.align_offset += get_align_bits(); } + if (filp && IS_ENABLED(CONFIG_FS_DAX_PMD) && IS_DAX(file_inode(filp))) { + unsigned long off_end = info.align_offset + len; + unsigned long off_pmd = round_up(info.align_offset, PMD_SIZE); + + if ((off_end > off_pmd) && ((off_end - off_pmd) >= PMD_SIZE)) + info.align_mask |= (PMD_SIZE - 1); + } addr = vm_unmapped_area(&info); if (!(addr & ~PAGE_MASK)) return addr; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org