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>
---
v2: Improve error message.
Fall back to a warning if mode sense failed.
Check unmarshal return value.
---
block/iscsi.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
diff --git a/block/iscsi.c b/block/iscsi.c
index 233f462..dcacbca 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1219,6 +1219,44 @@ static void iscsi_attach_aio_context(BlockDriverState
*bs,
qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + NOP_INTERVAL);
}
+static bool iscsi_is_write_protected(IscsiLun *iscsilun)
+{
+ struct scsi_task *task;
+ struct scsi_mode_sense *ms = NULL;
+
+ task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
+ 1, SCSI_MODESENSE_PC_CURRENT,
+ 0x3F,
+ 0, 255);
+
+ if (task == NULL) {
+ error_report("Failed to send MODE_SENSE6 command: %s",
+ iscsi_get_error(iscsilun->iscsi));
+ goto out;
+ }
+
+ if (task->status != SCSI_STATUS_GOOD) {
+ error_report("MODE_SENSE6 failed: %s",
+ iscsi_get_error(iscsilun->iscsi));
+ goto out;
+ }
+ ms = scsi_datain_unmarshall(task);
+ if (!ms) {
+ error_report("MODE_SENSE6 failed: %s",
+ iscsi_get_error(iscsilun->iscsi));
+ goto out;
+ }
+out:
+ if (task) {
+ scsi_free_scsi_task(task);
+ }
+ if (!ms) {
+ error_report("Assuming write enabled");
+ return false;
+ }
+ return ms->device_specific_parameter & 0x80;
+}
+
/*
* We support iscsi url's on the form
* iscsi://[<username>%<password>@]<host>[:<port>]/<targetname>/<lun>
@@ -1339,6 +1377,14 @@ 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)
+ && iscsi_is_write_protected(iscsilun)) {
+ error_setg(errp, "Cannot open a write protected LUN as read-write");
+ ret = -EPERM;
+ goto out;
+ }
+
iscsi_readcapacity_sync(iscsilun, &local_err);
if (local_err != NULL) {
error_propagate(errp, local_err);
--
1.9.3
