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From: | Peter Lieven |
Subject: | Re: [Qemu-devel] [PATCH] iscsi: Refuse to open as writable if the LUN is write protected |
Date: | Thu, 30 Oct 2014 11:52:39 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 30.10.2014 11:50, Fam Zheng wrote:
On Thu, 10/30 11:27, Peter Lieven wrote:On 29.10.2014 19:28, Paolo Bonzini wrote:On 10/29/2014 05:18 PM, Peter Lieven wrote:Am 29.10.2014 um 14:31 schrieb Paolo Bonzini:On 10/29/2014 02:13 PM, Fam Zheng wrote:Before, when a write protected iSCSI target is attached as scsi-disk with BDRV_O_RDWR, we report it as writable, while in fact all writes will fail. One way to improve this is to report write protect flag as true to guest, but a even better way is to refuse using a write protected LUN to guest. Target write protect flag is checked with a mode sense query. Signed-off-by: Fam Zheng <address@hidden> --- block/iscsi.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/block/iscsi.c b/block/iscsi.c index 233f462..c154928 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -1339,6 +1339,36 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags, scsi_free_scsi_task(task); task = NULL; + /* Check the write protect flag of the LUN if we want to write */ + if (flags & BDRV_O_RDWR) { + struct scsi_mode_sense *ms; + + task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun, + 1, SCSI_MODESENSE_PC_CURRENT, + 0x3F, + 0, 255); + + if (task == NULL) { + error_setg(errp, "Failed to send MODE_SENSE10 command: %s\n",This is MODE SENSE(6). Fixed and applied. Paolo+ iscsi_get_error(iscsilun->iscsi)); + ret = -EINVAL; + goto out; + } + + if (task->status != SCSI_STATUS_GOOD) { + error_setg(errp, "MODE_SENSE10 failed: %s\n", + iscsi_get_error(iscsi)); + ret = -EINVAL; + goto out; + } + ms = scsi_datain_unmarshall(task);scsi_datain_unmarshall may fail. You need to check for NULL here.Thanks for the remark, I fixed this too. PaoloI am not 100% happy with this patch as it may break support for some targets. It seems that MODESENSE is somewhat tricky with some targets. See function sd_read_write_protect_flag in <http://lxr.free-electrons.com/ident?i=sd_read_write_protect_flag>drivers/scsi/sd.c of the Linux kernel. I would not fail if this modesense fails, but just assume write enabled. Maybe drop a warning.OK.In the command itself: 0x3F => SCSI_MODEPAGE_RETURN_ALL_PAGESThat requires a newer version of libiscsi than we currently check for. Seeing drivers/scsi/sd.c used 0x3F, I left this.
Okay, I wasn't ware. It seems it went in for 1.10.0 and we check for 1.9.0, right?
Can you please post the resulting patch somewhere for review.I'll fix this with the error messsage and unmarshal failure and post another version.
Thanks, Peter
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