From d27418aaf8bcb21f3f9b54a57427a0ae4f025bf7 Mon Sep 17 00:00:00 2001 From: David Jeffery Date: Tue, 4 Nov 2025 10:46:23 -0500 Subject: [PATCH] scsi: st: Skip buffer flush for information ioctls MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit With commit 9604eea5bd3a ("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: David Jeffery Tested-by: Laurence Oberman Acked-by: Kai Mäkisara Reviewed-by: John Meneghini Tested-by: John Meneghini Link: https://patch.msgid.link/20251104154709.6436-2-djeffery@redhat.com Signed-off-by: Martin K. Petersen --- drivers/scsi/st.c | 44 ++++++++++++++++++++++++-------------------- 1 file changed, 24 insertions(+), 20 deletions(-) diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index 505850f009ca..168f25e4aaa3 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -3542,31 +3542,35 @@ static long st_common_ioctl(struct scsi_tape *STp, struct st_modedef *STm, goto out; } - 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; + 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); - 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, (void __user *)arg); if (!retval && cmd_in == SCSI_IOCTL_STOP_UNIT) {