From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f52.google.com (mail-wg0-f52.google.com [74.125.82.52]) by kanga.kvack.org (Postfix) with ESMTP id 0969C6B0069 for ; Wed, 8 Oct 2014 16:11:09 -0400 (EDT) Received: by mail-wg0-f52.google.com with SMTP id a1so12221749wgh.23 for ; Wed, 08 Oct 2014 13:11:09 -0700 (PDT) Received: from jenni2.inet.fi (mta-out1.inet.fi. [62.71.2.197]) by mx.google.com with ESMTP id cw9si1187303wjc.49.2014.10.08.13.11.08 for ; Wed, 08 Oct 2014 13:11:08 -0700 (PDT) Date: Wed, 8 Oct 2014 23:11:00 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH v1 5/7] dax: Add huge page fault support Message-ID: <20141008201100.GB9232@node.dhcp.inet.fi> References: <1412774729-23956-1-git-send-email-matthew.r.wilcox@intel.com> <1412774729-23956-6-git-send-email-matthew.r.wilcox@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412774729-23956-6-git-send-email-matthew.r.wilcox@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox On Wed, Oct 08, 2014 at 09:25:27AM -0400, Matthew Wilcox wrote: > + > + pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; > + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; > + if (pgoff >= size) > + return VM_FAULT_SIGBUS; > + /* If the PMD would cover blocks out of the file */ > + if ((pgoff | PG_PMD_COLOUR) >= size) > + return VM_FAULT_FALLBACK; IIUC, zero pading would work too. > + > + memset(&bh, 0, sizeof(bh)); > + block = ((sector_t)pgoff & ~PG_PMD_COLOUR) << (PAGE_SHIFT - blkbits); > + > + /* Start by seeing if we already have an allocated block */ > + bh.b_size = PMD_SIZE; > + length = get_block(inode, block, &bh, 0); This makes me confused. get_block() return zero on success, right? Why the var called 'lenght'? > + sector = bh.b_blocknr << (blkbits - 9); > + length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, bh.b_size); > + if (length < 0) > + goto sigbus; > + if (length < PMD_SIZE) > + goto fallback; > + if (pfn & PG_PMD_COLOUR) > + goto fallback; /* not aligned */ So, are you rely on pure luck to make get_block() allocate 2M aligned pfn? Not really productive. You would need assistance from fs and arch_get_unmapped_area() sides. -- Kirill A. Shutemov -- 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