From patchwork Fri Oct 12 21:11:00 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Roth X-Patchwork-Id: 191242 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 4AF572C008B for ; Sat, 13 Oct 2012 09:29:52 +1100 (EST) Received: from localhost ([::1]:40591 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TMmXl-0000Oy-IC for incoming@patchwork.ozlabs.org; Fri, 12 Oct 2012 17:13:17 -0400 Received: from eggs.gnu.org ([208.118.235.92]:42535) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TMmWL-0006Bm-BH for qemu-devel@nongnu.org; Fri, 12 Oct 2012 17:11:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TMmWK-00064o-0C for qemu-devel@nongnu.org; Fri, 12 Oct 2012 17:11:49 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:36593) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TMmWJ-0005iK-Oz for qemu-devel@nongnu.org; Fri, 12 Oct 2012 17:11:47 -0400 Received: by mail-ie0-f173.google.com with SMTP id 17so5335456iea.4 for ; Fri, 12 Oct 2012 14:11:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references; bh=UyoOgT3OdYUs1ptUsHq07h7+V4TW7KFSEWswtjM8MQE=; b=Hx0ft1r2n77y7pj9XDWoNyDcGacUUeOosGQ/npm+LH2J0G/77bDHjqdwR4Y9dG7HQU 0/V5oYpYwfwKVCq5YPQHh/SQ7KPWtU3MiFhWvOyKWrdx8j40x+UCeeKTl6zKTBx1RFpg qvta921iBgjaUh7miTv1Ll153TbqAZTF/m+0vl4Bfo6wef2y2ptAYQCAjua0xb0UtQu1 H5fTRAmsEMD3L1CoEGudKkk2KB8SZ1+KqHCEaKCnJYga1S8GyBP1cZnFyxQ7XUkOcFvW jDd1wLIziCiKBYZt4FtXbBw4abKnZi9OsOnW0pSobSexSxFrtx0eS9RctX9Obk1D0sw+ kYeA== Received: by 10.50.95.231 with SMTP id dn7mr3430425igb.36.1350076307599; Fri, 12 Oct 2012 14:11:47 -0700 (PDT) Received: from loki.morrigu.org (cpe-72-179-62-111.austin.res.rr.com. [72.179.62.111]) by mx.google.com with ESMTPS id uj11sm2454777igb.15.2012.10.12.14.11.46 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 12 Oct 2012 14:11:46 -0700 (PDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Fri, 12 Oct 2012 16:11:00 -0500 Message-Id: <1350076268-18461-19-git-send-email-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1350076268-18461-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1350076268-18461-1-git-send-email-mdroth@linux.vnet.ibm.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 209.85.223.173 Cc: kwolf@redhat.com, peter.maydell@linaro.org, aliguori@us.ibm.com, blauwirbel@gmail.com, pbonzini@redhat.com Subject: [Qemu-devel] [PATCH v4 18/26] qom-fuse: workaround for truncated properties > 4096 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org We currently hard-code property size at 4096 for the purposes of getattr()/stat()/etc. For 'state' properties we can exceed this easily, leading to truncated responses. Instead, for a particular property, make it max(4096, most_recent_property_size * 2). This allows some head-room for properties that change size periodically (numbers, strings, state properties containing arrays, etc) Also, implement a simple property cache to avoid spinning on qom-get if an application reads beyond the actual size. This also allows us to use a snapshot of a single qom-get that persists across read()'s. Old Cache entries are evicted as soon as we attempt to read() from offset 0 again. Reviewed-by: Anthony Liguori Reviewed-by: Paolo Bonzini Signed-off-by: Michael Roth --- QMP/qom-fuse | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/QMP/qom-fuse b/QMP/qom-fuse index b4a4eb3..bbad0de 100755 --- a/QMP/qom-fuse +++ b/QMP/qom-fuse @@ -26,6 +26,7 @@ class QOMFS(Fuse): self.qmp.connect() self.ino_map = {} self.ino_count = 1 + self.prop_cache = {} def get_ino(self, path): if self.ino_map.has_key(path): @@ -67,12 +68,16 @@ class QOMFS(Fuse): if not self.is_property(path): return -ENOENT - path, prop = path.rsplit('/', 1) - try: - data = str(self.qmp.command('qom-get', path=path, property=prop)) - data += '\n' # make values shell friendly - except: - return -EPERM + # avoid extra calls to qom-get by using cached value when offset > 0 + if offset == 0 or not self.prop_cache.has_key(path): + directory, prop = path.rsplit('/', 1) + try: + resp = str(self.qmp.command('qom-get', path=directory, property=prop)) + self.prop_cache[path] = resp + '\n' # make values shell friendly + except: + return -EPERM + + data = self.prop_cache[path] if offset > len(data): return '' @@ -111,13 +116,18 @@ class QOMFS(Fuse): 0, 0)) elif self.is_property(path): + directory, prop = path.rsplit('/', 1) + try: + resp = str(self.qmp.command('qom-get', path=directory, property=prop)) + except: + return -ENOENT value = posix.stat_result((0644 | stat.S_IFREG, self.get_ino(path), 0, 1, 1000, 1000, - 4096, + max(len(resp) * 2, 4096), 0, 0, 0))