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 <f...@redhat.com>
---
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.
Paolo
I 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.
In the command itself:
0x3F => SCSI_MODEPAGE_RETURN_ALL_PAGES
Can you please post the resulting patch somewhere for review.
Thanks,
Peter
