Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756120Ab3JGUWG (ORCPT ); Mon, 7 Oct 2013 16:22:06 -0400 Received: from e23smtp07.au.ibm.com ([202.81.31.140]:34780 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755801Ab3JGUWB (ORCPT ); Mon, 7 Oct 2013 16:22:01 -0400 From: Robert C Jennings To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Rik van Riel , Andrea Arcangeli , Dave Hansen , Robert C Jennings , Matt Helsley , Anthony Liguori , Michael Roth , Lei Li , Leonardo Garcia , Vlastimil Babka Subject: [PATCH 1/2] vmsplice: unmap gifted pages for recipient Date: Mon, 7 Oct 2013 15:21:32 -0500 Message-Id: <1381177293-27125-2-git-send-email-rcj@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1381177293-27125-1-git-send-email-rcj@linux.vnet.ibm.com> References: <1381177293-27125-1-git-send-email-rcj@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100720-0260-0000-0000-000003BDE37D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4309 Lines: 144 Introduce use of the unused SPLICE_F_MOVE flag for vmsplice to zap pages. When vmsplice is called with flags (SPLICE_F_GIFT | SPLICE_F_MOVE) the writer's gift'ed pages would be zapped. This patch supports further work to move vmsplice'd pages rather than copying them. That patch has the restriction that the page must not be mapped by the source for the move, otherwise it will fall back to copying the page. Signed-off-by: Matt Helsley Signed-off-by: Robert C Jennings --- Since the RFC went out I have coalesced the zap_page_range() call to operate on VMAs rather than calling this for each page. For a 256MB vmsplice this reduced the write side 50% from the RFC. --- fs/splice.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++- include/linux/splice.h | 1 + 2 files changed, 51 insertions(+), 1 deletion(-) diff --git a/fs/splice.c b/fs/splice.c index 3b7ee65..a62d61e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -188,12 +188,17 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, { unsigned int spd_pages = spd->nr_pages; int ret, do_wakeup, page_nr; + struct vm_area_struct *vma; + unsigned long user_start, user_end; ret = 0; do_wakeup = 0; page_nr = 0; + vma = NULL; + user_start = user_end = 0; pipe_lock(pipe); + down_read(¤t->mm->mmap_sem); for (;;) { if (!pipe->readers) { @@ -212,8 +217,44 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, buf->len = spd->partial[page_nr].len; buf->private = spd->partial[page_nr].private; buf->ops = spd->ops; - if (spd->flags & SPLICE_F_GIFT) + if (spd->flags & SPLICE_F_GIFT) { + unsigned long useraddr = + spd->partial[page_nr].useraddr; + + if ((spd->flags & SPLICE_F_MOVE) && + !buf->offset && + (buf->len == PAGE_SIZE)) { + /* Can move page aligned buf, gather + * requests to make a single + * zap_page_range() call per VMA + */ + if (vma && (useraddr == user_end) && + ((useraddr + PAGE_SIZE) <= + vma->vm_end)) { + /* same vma, no holes */ + user_end += PAGE_SIZE; + } else { + if (vma) + zap_page_range(vma, + user_start, + (user_end - + user_start), + NULL); + vma = find_vma_intersection( + current->mm, + useraddr, + (useraddr + + PAGE_SIZE)); + if (!IS_ERR_OR_NULL(vma)) { + user_start = useraddr; + user_end = (useraddr + + PAGE_SIZE); + } else + vma = NULL; + } + } buf->flags |= PIPE_BUF_FLAG_GIFT; + } pipe->nrbufs++; page_nr++; @@ -255,6 +296,10 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, pipe->waiting_writers--; } + if (vma) + zap_page_range(vma, user_start, (user_end - user_start), NULL); + + up_read(¤t->mm->mmap_sem); pipe_unlock(pipe); if (do_wakeup) @@ -485,6 +530,7 @@ fill_it: spd.partial[page_nr].offset = loff; spd.partial[page_nr].len = this_len; + spd.partial[page_nr].useraddr = index << PAGE_CACHE_SHIFT; len -= this_len; loff = 0; spd.nr_pages++; @@ -656,6 +702,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos, this_len = min_t(size_t, vec[i].iov_len, res); spd.partial[i].offset = 0; spd.partial[i].len = this_len; + spd.partial[i].useraddr = (unsigned long)vec[i].iov_base; if (!this_len) { __free_page(spd.pages[i]); spd.pages[i] = NULL; @@ -1475,6 +1522,8 @@ static int get_iovec_page_array(const struct iovec __user *iov, partial[buffers].offset = off; partial[buffers].len = plen; + partial[buffers].useraddr = (unsigned long)base; + base = (void*)((unsigned long)base + PAGE_SIZE); off = 0; len -= plen; diff --git a/include/linux/splice.h b/include/linux/splice.h index 74575cb..56661e3 100644 --- a/include/linux/splice.h +++ b/include/linux/splice.h @@ -44,6 +44,7 @@ struct partial_page { unsigned int offset; unsigned int len; unsigned long private; + unsigned long useraddr; }; /* -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/