scsi: st: Add MTIOCGET and MTLOAD to ioctls allowed after device reset

[ Upstream commit 0b120edb37dc9dd8ca82893d386922eb6b16f860 ]

Most drives rewind the tape when the device is reset. Reading and writing
are not allowed until something is done to make the tape position match the
user's expectation (e.g., rewind the tape). Add MTIOCGET and MTLOAD to
operations allowed after reset. MTIOCGET is modified to not touch the tape
if pos_unknown is non-zero. The tape location is known after MTLOAD.

Signed-off-by: Kai Mäkisara <Kai.Makisara@kolumbus.fi>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219419#c14
Link: https://lore.kernel.org/r/20241106095723.63254-3-Kai.Makisara@kolumbus.fi
Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Tested-by: John Meneghini <jmeneghi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index c08518258f0016b3e7bf2b707f0b71c33c21610c..3b819c6b15a569609cb7281652b0b8e3a65202b6 100644 (file)
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -3505,6 +3505,7 @@ static long st_ioctl_common(struct file *file, unsigned int cmd_in, void __user
        int i, cmd_nr, cmd_type, bt;
        int retval = 0;
        unsigned int blk;
+       bool cmd_mtiocget;
        struct scsi_tape *STp = file->private_data;
        struct st_modedef *STm;
        struct st_partstat *STps;
@@ -3618,6 +3619,7 @@ static long st_ioctl_common(struct file *file, unsigned int cmd_in, void __user
                         */
                        if (mtc.mt_op != MTREW &&
                            mtc.mt_op != MTOFFL &&
+                           mtc.mt_op != MTLOAD &&
                            mtc.mt_op != MTRETEN &&
                            mtc.mt_op != MTERASE &&
                            mtc.mt_op != MTSEEK &&
@@ -3731,17 +3733,28 @@ static long st_ioctl_common(struct file *file, unsigned int cmd_in, void __user
                goto out;
        }
 
+       cmd_mtiocget = cmd_type == _IOC_TYPE(MTIOCGET) && cmd_nr == _IOC_NR(MTIOCGET);
+
        if ((i = flush_buffer(STp, 0)) < 0) {
-               retval = i;
-               goto out;
-       }
-       if (STp->can_partitions &&
-           (i = switch_partition(STp)) < 0) {
-               retval = i;
-               goto out;
+               if (cmd_mtiocget && STp->pos_unknown) {
+                       /* flush fails -> modify status accordingly */
+                       reset_state(STp);
+                       STp->pos_unknown = 1;
+               } else { /* return error */
+                       retval = i;
+                       goto out;
+               }
+       } else { /* flush_buffer succeeds */
+               if (STp->can_partitions) {
+                       i = switch_partition(STp);
+                       if (i < 0) {
+                               retval = i;
+                               goto out;
+                       }
+               }
        }
 
-       if (cmd_type == _IOC_TYPE(MTIOCGET) && cmd_nr == _IOC_NR(MTIOCGET)) {
+       if (cmd_mtiocget) {
                struct mtget mt_status;
 
                if (_IOC_SIZE(cmd_in) != sizeof(struct mtget)) {