From patchwork Fri Sep 21 14:07:37 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Roth X-Patchwork-Id: 185809 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 5282A2C00B9 for ; Sat, 22 Sep 2012 02:06:26 +1000 (EST) Received: from localhost ([::1]:37240 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF3vc-0003QF-TG for incoming@patchwork.ozlabs.org; Fri, 21 Sep 2012 10:10:00 -0400 Received: from eggs.gnu.org ([208.118.235.92]:41270) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF3uM-0001oJ-2R for qemu-devel@nongnu.org; Fri, 21 Sep 2012 10:08:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TF3uE-0007KI-8x for qemu-devel@nongnu.org; Fri, 21 Sep 2012 10:08:41 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:34534) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF3uE-0007Cw-4C for qemu-devel@nongnu.org; Fri, 21 Sep 2012 10:08:34 -0400 Received: by mail-ie0-f173.google.com with SMTP id 17so990551iea.4 for ; Fri, 21 Sep 2012 07:08:34 -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=ZDk/E1K1bQ0KMHyLdFCAfTte6h6BdZ8Zo9GJ4s2iZek=; b=oR/ESjKER1Mmntx2Yg++KwADsIPI/pvRPbDJKCIy47Uw8UZsktqT3FP+BIcttSa4Dt 10rhbUZDlN9P/eMaoH6MFpXqO6B8xFuZ3BNkT+2IVFTCbecWaHNkExBTMQ9OwQSIL8xz OmGKMfkl3oDTo3CX/ZGXjm/Kg5LLhAkwXqfZ2n0D3lQA27BcIPdopR4vV2ikhi9MmtBE orsyqIha5MHfCza6+/7uu+7GF6CTfSZi5iJXEyN8jMpVwnXBmL+dhUKwzfcSitvx6aZc kpi6rMY6M/nke7tCdvxVnzWeC5ssCYDvLe8fRmfv9JcNjLd1RSlOutp7TjPg9lu1GWPE uk1w== Received: by 10.50.51.232 with SMTP id n8mr1726008igo.68.1348236513962; Fri, 21 Sep 2012 07:08:33 -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 ua5sm17301156igb.10.2012.09.21.07.08.32 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 21 Sep 2012 07:08:33 -0700 (PDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Fri, 21 Sep 2012 09:07:37 -0500 Message-Id: <1348236465-23124-15-git-send-email-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1348236465-23124-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1348236465-23124-1-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: blauwirbel@gmail.com, peter.maydell@linaro.org, aliguori@us.ibm.com, eblake@redhat.com Subject: [Qemu-devel] [PATCH 14/22] 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 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))