From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:33937) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RROzT-000848-W3 for qemu-devel@nongnu.org; Fri, 18 Nov 2011 09:00:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RROzP-0002Zi-Dq for qemu-devel@nongnu.org; Fri, 18 Nov 2011 09:00:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:15901) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RROzP-0002ZS-4C for qemu-devel@nongnu.org; Fri, 18 Nov 2011 09:00:23 -0500 From: Kevin Wolf Date: Fri, 18 Nov 2011 15:03:13 +0100 Message-Id: <1321624993-19033-10-git-send-email-kwolf@redhat.com> In-Reply-To: <1321624993-19033-1-git-send-email-kwolf@redhat.com> References: <1321624993-19033-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 9/9] scsi-block: always use SG_IO for MMC devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Paolo Bonzini CD burning messes up the state of the host page cache and host block device. Just pass all operations down to the device, even though that might have slightly worse performance. Everything else just is not reliable in combination with burning. Reported-by: Thomas Schmitt Signed-off-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- hw/scsi-disk.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-) diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c index e3690ec..673948c 100644 --- a/hw/scsi-disk.c +++ b/hw/scsi-disk.c @@ -1703,8 +1703,20 @@ static SCSIRequest *scsi_block_new_request(SCSIDevice *d, uint32_t tag, case WRITE_VERIFY_10: case WRITE_VERIFY_12: case WRITE_VERIFY_16: - return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun, - hba_private); + /* MMC writing cannot be done via pread/pwrite, because it sometimes + * involves writing beyond the maximum LBA or to negative LBA (lead-in). + * And once you do these writes, reading from the block device is + * unreliable, too. It is even possible that reads deliver random data + * from the host page cache (this is probably a Linux bug). + * + * We might use scsi_disk_reqops as long as no writing commands are + * seen, but performance usually isn't paramount on optical media. So, + * just make scsi-block operate the same as scsi-generic for them. + */ + if (s->qdev.type != TYPE_ROM) { + return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun, + hba_private); + } } return scsi_req_alloc(&scsi_generic_req_ops, &s->qdev, tag, lun, -- 1.7.6.4