From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=59827 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OxgTL-0004TK-1P for qemu-devel@nongnu.org; Mon, 20 Sep 2010 09:31:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OxgTJ-00006E-Ns for qemu-devel@nongnu.org; Mon, 20 Sep 2010 09:31:55 -0400 Received: from mtagate7.de.ibm.com ([195.212.17.167]:60901) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OxgTJ-000060-BA for qemu-devel@nongnu.org; Mon, 20 Sep 2010 09:31:53 -0400 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate7.de.ibm.com (8.13.1/8.13.1) with ESMTP id o8KDVofa025372 for ; Mon, 20 Sep 2010 13:31:50 GMT Received: from d12av03.megacenter.de.ibm.com (d12av03.megacenter.de.ibm.com [9.149.165.213]) by d12nrmr1607.megacenter.de.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o8KDViQO4124774 for ; Mon, 20 Sep 2010 15:31:50 +0200 Received: from d12av03.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av03.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id o8KDViOO016498 for ; Mon, 20 Sep 2010 15:31:44 +0200 From: Stefan Hajnoczi Date: Mon, 20 Sep 2010 14:31:33 +0100 Message-Id: <1284989493-13154-1-git-send-email-stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH] blkverify: Handle overlapping I/O vector buffers List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi When blkverify clones an I/O vector in order to perform mirrored reads and then compare their contents, it does not take into account the layout of individual buffers. It turns out this is important because guests may issue requests with overlapping buffers and the results differ depending on how buffers are overlapped. This patch introduces logic to honor overlap relationships when cloning I/O vectors. Signed-off-by: Stefan Hajnoczi --- block/blkverify.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 60 insertions(+), 2 deletions(-) diff --git a/block/blkverify.c b/block/blkverify.c index 97717a6..524b777 100644 --- a/block/blkverify.c +++ b/block/blkverify.c @@ -166,17 +166,75 @@ static ssize_t blkverify_iovec_compare(QEMUIOVector *a, QEMUIOVector *b) return -1; } +typedef struct { + int src_index; + struct iovec *src_iov; + void *dest_base; +} IOVectorSortElem; + +static int sortelem_cmp_src_base(const void *a, const void *b) +{ + const IOVectorSortElem *elem_a = a; + const IOVectorSortElem *elem_b = b; + + /* Don't overflow */ + if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) { + return -1; + } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) { + return 1; + } else { + return 0; + } +} + +static int sortelem_cmp_src_index(const void *a, const void *b) +{ + const IOVectorSortElem *elem_a = a; + const IOVectorSortElem *elem_b = b; + + return elem_a->src_index - elem_b->src_index; +} + /** * Copy contents of I/O vector + * + * The relative relationships of overlapping iovecs are preserved. This is + * necessary to ensure identical semantics in the cloned I/O vector. */ static void blkverify_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf) { + IOVectorSortElem sortelems[src->niov]; + void *last_end; int i; + /* Sort by source iovecs by base address */ + for (i = 0; i < src->niov; i++) { + sortelems[i].src_index = i; + sortelems[i].src_iov = &src->iov[i]; + } + qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base); + + /* Allocate buffer space taking into account overlapping iovecs */ + last_end = NULL; + for (i = 0; i < src->niov; i++) { + struct iovec *cur = sortelems[i].src_iov; + ptrdiff_t rewind = 0; + + /* Detect overlap */ + if (last_end && last_end > cur->iov_base) { + rewind = last_end - cur->iov_base; + } + + sortelems[i].dest_base = buf - rewind; + buf += cur->iov_len - MIN(rewind, cur->iov_len); + last_end = MAX(cur->iov_base + cur->iov_len, last_end); + } + + /* Sort by source iovec index and build destination iovec */ + qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index); for (i = 0; i < src->niov; i++) { - qemu_iovec_add(dest, buf, src->iov[i].iov_len); - buf += src->iov[i].iov_len; + qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len); } } -- 1.7.1