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iscsi: Refuse to open as writable if the LUN is write protected

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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 <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Fam Zheng 2014-10-30 19:23:46 +08:00 committed by Paolo Bonzini
parent 076893d3d0
commit c1d4096b0f
1 changed files with 42 additions and 0 deletions
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42
block/iscsi.c
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@ -1219,6 +1219,40 @@ 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;
bool wrprotected = false;
task = iscsi_modesense6_sync(iscsilun->iscsi, iscsilun->lun,
1, SCSI_MODESENSE_PC_CURRENT,
0x3F, 0, 255);
if (task == NULL) {
error_report("iSCSI: Failed to send MODE_SENSE(6) command: %s",
iscsi_get_error(iscsilun->iscsi));
goto out;
}
if (task->status != SCSI_STATUS_GOOD) {
error_report("iSCSI: Failed MODE_SENSE(6), LUN assumed writable");
goto out;
}
ms = scsi_datain_unmarshall(task);
if (!ms) {
error_report("iSCSI: Failed to unmarshall MODE_SENSE(6) data: %s",
iscsi_get_error(iscsilun->iscsi));
goto out;
}
wrprotected = ms->device_specific_parameter & 0x80;
out:
if (task) {
scsi_free_scsi_task(task);
}
return wrprotected;
}
/*
* We support iscsi url's on the form
* iscsi://[<username>%<password>@]<host>[:<port>]/<targetname>/<lun>
@ -1339,6 +1373,14 @@ 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 (iscsilun->type == TYPE_DISK && (flags & BDRV_O_RDWR) &&
iscsi_is_write_protected(iscsilun)) {
error_setg(errp, "Cannot open a write protected LUN as read-write");
ret = -EACCES;
goto out;
}
iscsi_readcapacity_sync(iscsilun, &local_err);
if (local_err != NULL) {
error_propagate(errp, local_err);