From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52751) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yqfkw-0002Ey-Mi for qemu-devel@nongnu.org; Fri, 08 May 2015 06:43:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yqfkr-0000Bh-Ky for qemu-devel@nongnu.org; Fri, 08 May 2015 06:43:46 -0400 Date: Fri, 8 May 2015 12:43:37 +0200 From: Kevin Wolf Message-ID: <20150508104337.GE4318@noname.redhat.com> References: <1430971496-32659-1-git-send-email-phoeagon@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430971496-32659-1-git-send-email-phoeagon@gmail.com> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v3] block/vdi: Use bdrv_flush after metadata updates List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhe Qiu Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com Am 07.05.2015 um 06:04 hat Zhe Qiu geschrieben: > From: phoeagon > > In reference to b0ad5a455d7e5352d4c86ba945112011dbeadfb8~078a458e077d6b0db262c4b05fee51d01de2d1d2, metadata writes to qcow2/cow/qcow/vpc/vmdk are all synced prior to succeeding writes. The justification for these patches (in 2010!) was more or less that we didn't know whether the implementations were safe without the flushes. Many of the flushes added back then have been removed again until today because they have turned out to be unnecessary. > Only when write is successful that bdrv_flush is called. > > Signed-off-by: Zhe Qiu Please describe why VDI needs this flush to be safe. This is best done by describing a case where not doing the flush would lead to image corruption in case of a crash. To my knowledge, the VDI driver is completely safe without it. Kevin