From patchwork Mon Aug 5 19:43:59 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Lutomirski X-Patchwork-Id: 264774 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 0AB062C00A2 for ; Tue, 6 Aug 2013 05:47:55 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754819Ab3HEToP (ORCPT ); Mon, 5 Aug 2013 15:44:15 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:36234 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754764Ab3HEToM (ORCPT ); Mon, 5 Aug 2013 15:44:12 -0400 Received: by mail-pd0-f171.google.com with SMTP id bv13so3621844pdb.2 for ; Mon, 05 Aug 2013 12:44:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references :in-reply-to:references:x-gm-message-state; bh=r1exJCPf0W5eIqHpy24Lx6/KSa5RIhDyRSPxGzn96tA=; b=UY3ZsA608AoAr0dSsGItVl/BmSAc2IrO6sJ2venvOQkKy7zf5FeVuCTSvhsZvHKx42 GhbodPnQAaLH3iiDfDFIdjtVceOpRWTvXtZGqAsGOFCSNddB8VxI5q3AsgKwZBIW4Siq B320f8F6WEWpFAhZEvpYWazHzn0FhpFt98LPOx3KG++cv6Fvztw+PERujofbW/vdk+mn V8L+2MYnisy2RGNunajrKBhC4ThHITDNjsHdpYeD09WMGokgsANgCjCZAPJvnYnz4krA KrI+Dl0Pw0kZ2NPYIsXEqgci1UkqM3FJA164irJcF8hi89JN6vn5dmzphcETcTsfcnFp EsTw== X-Received: by 10.66.121.131 with SMTP id lk3mr27303302pab.43.1375731851784; Mon, 05 Aug 2013 12:44:11 -0700 (PDT) Received: from localhost (50-76-60-73-ip-static.hfc.comcastbusiness.net. [50.76.60.73]) by mx.google.com with ESMTPSA id qf7sm1260548pac.14.2013.08.05.12.44.10 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 05 Aug 2013 12:44:11 -0700 (PDT) From: Andy Lutomirski To: linux-mm@kvack.org, linux-ext4@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski Subject: [RFC 1/3] mm: Add MADV_WILLWRITE to indicate that a range will be written to Date: Mon, 5 Aug 2013 12:43:59 -0700 Message-Id: X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: In-Reply-To: References: X-Gm-Message-State: ALoCoQnoh9OzgN572zYwmsX4Q9T2PNfLWsvMjjq8Afxz5R2moTq91jpbf88rEMrzIezH0oJyI2Ya Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org This should not cause data to be written to disk. It should, however, do any expensive operations that would otherwise happen on the first write fault to this range. Some day this may COW private mappings, allocate real memory instead of zero pages, etc. For now it just passes the request down to filesystems on shared writable mappings. Signed-off-by: Andy Lutomirski --- include/linux/mm.h | 12 ++++++++++++ include/uapi/asm-generic/mman-common.h | 3 +++ mm/madvise.c | 28 ++++++++++++++++++++++++++-- 3 files changed, 41 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f022460..d3c89ab 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -205,6 +205,18 @@ struct vm_operations_struct { * writable, if an error is returned it will cause a SIGBUS */ int (*page_mkwrite)(struct vm_area_struct *vma, struct vm_fault *vmf); + /* request to make future writes to this page fast. only called + * on shared writable maps. return 0 on success (or if there's + * nothing to do). + * + * return the number of bytes for which the operation worked (i.e. + * zero if unsupported) or a negative error if something goes wrong. + * + * called with mmap_sem held for read. + */ + long (*willwrite)(struct vm_area_struct *vma, + unsigned long start, unsigned long end); + /* called by access_process_vm when get_user_pages() fails, typically * for use by special VMAs that can switch between memory and hardware */ diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h index 4164529..e65e97d 100644 --- a/include/uapi/asm-generic/mman-common.h +++ b/include/uapi/asm-generic/mman-common.h @@ -52,6 +52,9 @@ overrides the coredump filter bits */ #define MADV_DODUMP 17 /* Clear the MADV_NODUMP flag */ +#define MADV_WILLWRITE 18 /* Will write to this page, but maybe + only after a while */ + /* compatibility flags */ #define MAP_FILE 0 diff --git a/mm/madvise.c b/mm/madvise.c index 7055883..7b537fd 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -31,6 +31,7 @@ static int madvise_need_mmap_write(int behavior) case MADV_REMOVE: case MADV_WILLNEED: case MADV_DONTNEED: + case MADV_WILLWRITE: return 0; default: /* be safe, default to 1. list exceptions explicitly */ @@ -337,6 +338,24 @@ static long madvise_remove(struct vm_area_struct *vma, return error; } +static long madvise_willwrite(struct vm_area_struct * vma, + struct vm_area_struct ** prev, + unsigned long start, unsigned long end) +{ + *prev = vma; + + if (!(vma->vm_flags & VM_WRITE)) + return -EFAULT; + + if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) + return 0; /* Not yet supported */ + + if (!vma->vm_file || !vma->vm_ops || !vma->vm_ops->willwrite) + return 0; /* Not supported */ + + return vma->vm_ops->willwrite(vma, start, end); +} + #ifdef CONFIG_MEMORY_FAILURE /* * Error injection support for memory error handling. @@ -380,6 +399,8 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, return madvise_willneed(vma, prev, start, end); case MADV_DONTNEED: return madvise_dontneed(vma, prev, start, end); + case MADV_WILLWRITE: + return madvise_willwrite(vma, prev, start, end); default: return madvise_behavior(vma, prev, start, end, behavior); } @@ -407,6 +428,7 @@ madvise_behavior_valid(int behavior) #endif case MADV_DONTDUMP: case MADV_DODUMP: + case MADV_WILLWRITE: return 1; default: @@ -465,6 +487,7 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) int write; size_t len; struct blk_plug plug; + long sum_rets = 0; #ifdef CONFIG_MEMORY_FAILURE if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE) @@ -526,8 +549,9 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ error = madvise_vma(vma, &prev, start, tmp, behavior); - if (error) + if (error < 0) goto out; + sum_rets += error; start = tmp; if (prev && start < prev->vm_end) start = prev->vm_end; @@ -546,5 +570,5 @@ out: else up_read(¤t->mm->mmap_sem); - return error; + return error ? error : sum_rets; }