Merge: scsi: st: Skip buffer flush for information ioctls

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1762

JIRA: https://issues.redhat.com/browse/RHEL-115965

Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

Depends: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1677

With commit 9604eea ("scsi: st: Add third party poweron reset
handling") some customer tape applications fail from being unable to
complete ioctls to verify ID information for the device when there has
been any type of reset event to their tape devices.

The st driver currently will fail all standard SCSI ioctls if a call to
flush_buffer() fails in st_ioctl(). This causes ioctls which otherwise
have no effect on tape state to succeed or fail based on events
unrelated to the requested ioctl.

This makes SCSI information ioctls unreliable after a reset even if no
buffering is in use. With a reset setting the pos_unknown field,
flush_buffer() will report failure and fail all ioctls. So any
application expecting to use ioctls to check the identify the device
will be unable to do so in such a state.

For SCSI information ioctls, avoid the need for a buffer flush and allow
the ioctls to execute regardless of buffer state.

Signed-off-by: John Meneghini <jmeneghi@redhat.com>

Approved-by: bgurney <bgurney@redhat.com>
Approved-by: Ewan D. Milne <emilne@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

drivers/scsi/st.c

@@ -3526,8 +3526,64 @@ static int partition_tape(struct scsi_tape *STp, int size)
 out:
 	return result;
 }
-
 
+/*
+ * Handles any extra state needed for ioctls which are not st-specific.
+ * Called with the scsi_tape lock held, released before return
+ */
+static long st_common_ioctl(struct scsi_tape *STp, struct st_modedef *STm,
+			    struct file *file, unsigned int cmd_in,
+			    unsigned long arg)
+{
+	int i, retval = 0;
+
+	if (!STm->defined) {
+		retval = -ENXIO;
+		goto out;
+	}
+
+	switch (cmd_in) {
+	case SCSI_IOCTL_GET_IDLUN:
+	case SCSI_IOCTL_GET_BUS_NUMBER:
+	case SCSI_IOCTL_GET_PCI:
+		break;
+	case SG_IO:
+	case SCSI_IOCTL_SEND_COMMAND:
+	case CDROM_SEND_PACKET:
+		if (!capable(CAP_SYS_RAWIO)) {
+			retval = -EPERM;
+			goto out;
+		}
+		fallthrough;
+	default:
+		if ((i = flush_buffer(STp, 0)) < 0) {
+			retval = i;
+			goto out;
+		} else { /* flush_buffer succeeds */
+			if (STp->can_partitions) {
+				i = switch_partition(STp);
+				if (i < 0) {
+					retval = i;
+					goto out;
+				}
+			}
+		}
+	}
+	mutex_unlock(&STp->lock);
+
+	retval = scsi_ioctl(STp->device, file->f_mode & FMODE_WRITE,
+			    cmd_in, (void __user *)arg);
+	if (!retval && cmd_in == SCSI_IOCTL_STOP_UNIT) {
+		/* unload */
+		STp->rew_at_close = 0;
+		STp->ready = ST_NO_TAPE;
+	}
+
+	return retval;
+out:
+	mutex_unlock(&STp->lock);
+	return retval;
+}
 
 /* The ioctl command */
 static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
@@ -3565,6 +3621,15 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
 	if (retval)
 		goto out;
 
+	switch (cmd_in) {
+	case MTIOCPOS:
+	case MTIOCGET:
+	case MTIOCTOP:
+		break;
+	default:
+		return st_common_ioctl(STp, STm, file, cmd_in, arg);
+	}
+
 	cmd_type = _IOC_TYPE(cmd_in);
 	cmd_nr = _IOC_NR(cmd_in);
 
@@ -3876,29 +3941,7 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
 		}
 		mt_pos.mt_blkno = blk;
 		retval = put_user_mtpos(p, &mt_pos);
-		goto out;
-	}
-	mutex_unlock(&STp->lock);
-
-	switch (cmd_in) {
-	case SG_IO:
-	case SCSI_IOCTL_SEND_COMMAND:
-	case CDROM_SEND_PACKET:
-		if (!capable(CAP_SYS_RAWIO))
-			return -EPERM;
-		break;
-	default:
-		break;
 	}
-
-	retval = scsi_ioctl(STp->device, file->f_mode & FMODE_WRITE, cmd_in, p);
-	if (!retval && cmd_in == SCSI_IOCTL_STOP_UNIT) {
-		/* unload */
-		STp->rew_at_close = 0;
-		STp->ready = ST_NO_TAPE;
-	}
-	return retval;
-
  out:
 	mutex_unlock(&STp->lock);
 	return retval;