From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:54591) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TG4QD-0007kz-Er for qemu-devel@nongnu.org; Mon, 24 Sep 2012 04:53:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TG4Q7-0001rP-EW for qemu-devel@nongnu.org; Mon, 24 Sep 2012 04:53:45 -0400 Message-ID: <50601F84.8020705@redhat.com> Date: Mon, 24 Sep 2012 10:53:24 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <1348072874-2096-1-git-send-email-sw@weilnetz.de> <20120922162920.GB14154@stefanha-thinkpad.localdomain> <505E0916.6030707@weilnetz.de> <50601043.2080209@redhat.com> <878vbzvmmn.fsf@blackfin.pond.sub.org> In-Reply-To: <878vbzvmmn.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] pflash: Avoid warnings from coverity List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: qemu-trivial@nongnu.org, Stefan Weil , qemu-devel@nongnu.org, Stefan Hajnoczi Am 24.09.2012 10:41, schrieb Markus Armbruster: > Kevin Wolf writes: > >> Am 22.09.2012 20:53, schrieb Stefan Weil: >>> Am 22.09.2012 18:29, schrieb Stefan Hajnoczi: >>>> On Wed, Sep 19, 2012 at 06:41:14PM +0200, Stefan Weil wrote: >>> [snip] >>>>> offset_end = (offset_end + 511) >> 9; >>>>> - bdrv_write(pfl->bs, offset, pfl->storage + (offset << 9), >>>>> - offset_end - offset); >>>>> + if (bdrv_write(pfl->bs, offset, pfl->storage + (offset << 9), >>>>> + offset_end - offset) == -1) { >>>> bdrv_write() returns -errno, not -1. >>> >>> Thanks. It looks like we have more code which uses the wrong check >>> (and which I copied). So more patches are needed. >>> >>> Should we also replace code which does bdrv_write() != 0 or !bdrv_write() >>> by bdrv_write() < 0 to get more uniform code (and the same for bdrv_read*), >>> even it is not strictly wrong? >>> >>> Maybe Kevin as block maintainer should decide that. >> >> Yes, I very much prefer ret < 0 checks for all block layer functions. >> >>>>> + fprintf(stderr, "pflash: Error writing to flash storage\n"); >>>>> + } >>>> Please report the errno and possibly bdrv_get_device_name() to uniquely >>>> identify this block device. >>> >>> That would be overkill here: writing flash memory is not used very >>> often (even on real hardware it is typically only used for firmware >>> updates). I expect that anyone who does a firmware update in a >>> QEMU guest will know the name of the flash image file. >>> >>> Usually I replace the flash image file on the QEMU host when I want >>> to exchange the firmware (much easier than flashing in the guest). >>> >>> Reporting errno might be more reasonable.Are there other values than >>> EIO (e.g. defective media) and ENOSPC (disk full) which could occur? >> >> Basically anything that the OS can return. The block layer may >> internally generate things like -EACCES for writing to read-only images, >> or -ENOMEDIUM (not sure if it's possible for pflash). >> >>> A common solution for all users of bdrv_write in the block layer >>> would be even better. VirtualBox for example stops the guest when >>> ENOSPC (disk full) occurs, so it's possible for users to fix that >>> and resume the emulation. >> >> virtio-blk/IDE/scsi-disk do that. > > Doing it in the block layer for all devices would be cleaner > conceptually. If I remember correctly, we did it in devices instead, > because that was much simpler. I believe today it wouldn't be too hard to implement the request queueing in the block layer. However, we can't change it without breaking migration, we'd need a VMState for the block layer. Kevin