scsi: add SG_SCSI_RESET_NO_ESCALATE flag to SG_SCSI_RESET ioctl

Further to a January 2013 thread titled: "[PATCH] SG_SCSI_RESET ioctl
should only perform requested operation" by Jeremy Linton a patch (v3)
is presented that expands the existing ioctl to include "no_escalate"
versions to the existing resets. This requires no changes to SCSI low
level drivers (LLDs); it adds several more finely tuned reset options
to the user space. For example:

   /* This call remains the same, with the same escalating semantics
    * if the device (LU) reset fail. That is: on failure to try a
    * target reset and if that fails, try a bus reset, and if that fails
    * try a host (i.e. LLD) reset. */
   val = SG_SCSI_RESET_DEVICE;
   res = ioctl(<sg_or_block_fd>, SG_SCSI_RESET, &val);

   /* What follows is a new option introduced by this patch series. Only
    * a device reset is attempted. If that fails then an appropriate
    * error code is provided. N.B. There is no reset escalation. */
   val = SG_SCSI_RESET_DEVICE | SG_SCSI_RESET_NO_ESCALATE;
   res = ioctl(<sg_or_block_fd>, SG_SCSI_RESET, &val);

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Jeremy Linton <jlinton@tributary.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

5 files changed, 43 insertions, 14 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index bc5ff6ff9c79..0ed666112b4f 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -2366,8 +2366,18 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
                         break;
                 /* FALLTHROUGH */
         case SCSI_TRY_RESET_HOST:
+        case SCSI_TRY_RESET_HOST | SCSI_TRY_RESET_NO_ESCALATE:
                 rtn = scsi_try_host_reset(scmd);
                 break;
+        case SCSI_TRY_RESET_DEVICE | SCSI_TRY_RESET_NO_ESCALATE:
+                rtn = scsi_try_bus_device_reset(scmd);
+                break;
+        case SCSI_TRY_RESET_TARGET | SCSI_TRY_RESET_NO_ESCALATE:
+                rtn = scsi_try_target_reset(scmd);
+                break;
+        case SCSI_TRY_RESET_BUS | SCSI_TRY_RESET_NO_ESCALATE:
+                rtn = scsi_try_bus_reset(scmd);
+                break;
         default:
                 rtn = FAILED;
         }
diff --git a/drivers/scsi/scsi_ioctl.c b/drivers/scsi/scsi_ioctl.c
index 1aaaf43c6803..12fe676d1343 100644
--- a/drivers/scsi/scsi_ioctl.c
+++ b/drivers/scsi/scsi_ioctl.c
@@ -285,13 +285,14 @@ EXPORT_SYMBOL(scsi_ioctl);
  * scsi_nonblockable_ioctl() - Handle SG_SCSI_RESET
  * @sdev: scsi device receiving ioctl
  * @cmd: Must be SC_SCSI_RESET
- * @arg: pointer to int containing SG_SCSI_RESET_{DEVICE,BUS,HOST}
+ * @arg: pointer to int containing SG_SCSI_RESET_{DEVICE,TARGET,BUS,HOST}
+ *       possibly OR-ed with SG_SCSI_RESET_NO_ESCALATE
  * @ndelay: file mode O_NDELAY flag
  */
 int scsi_nonblockable_ioctl(struct scsi_device *sdev, int cmd,
                             void __user *arg, int ndelay)
 {
-        int val, result;
+        int val, val2, result;
 
         /* The first set of iocts may be executed even if we're doing
          * error processing, as long as the device was opened
@@ -307,27 +308,32 @@ int scsi_nonblockable_ioctl(struct scsi_device *sdev, int cmd,
                 result = get_user(val, (int __user *)arg);
                 if (result)
                         return result;
+                if (val & SG_SCSI_RESET_NO_ESCALATE) {
+                        val &= ~SG_SCSI_RESET_NO_ESCALATE;
+                        val2 = SCSI_TRY_RESET_NO_ESCALATE;
+                } else
+                        val2 = 0;
                 if (val == SG_SCSI_RESET_NOTHING)
                         return 0;
                 switch (val) {
                 case SG_SCSI_RESET_DEVICE:
-                        val = SCSI_TRY_RESET_DEVICE;
+                        val2 |= SCSI_TRY_RESET_DEVICE;
                         break;
                 case SG_SCSI_RESET_TARGET:
-                        val = SCSI_TRY_RESET_TARGET;
+                        val2 |= SCSI_TRY_RESET_TARGET;
                         break;
                 case SG_SCSI_RESET_BUS:
-                        val = SCSI_TRY_RESET_BUS;
+                        val2 |= SCSI_TRY_RESET_BUS;
                         break;
                 case SG_SCSI_RESET_HOST:
-                        val = SCSI_TRY_RESET_HOST;
+                        val2 |= SCSI_TRY_RESET_HOST;
                         break;
                 default:
                         return -EINVAL;
                 }
                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                         return -EACCES;
-                return (scsi_reset_provider(sdev, val) ==
+                return (scsi_reset_provider(sdev, val2) ==
                         SUCCESS) ? 0 : -EIO;
         }
         return -ENODEV;
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 60354449d9ed..fe44c14f551e 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -847,7 +847,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 {
         void __user *p = (void __user *)arg;
         int __user *ip = p;
-        int result, val, read_only;
+        int result, val, val2, read_only;
         Sg_device *sdp;
         Sg_fd *sfp;
         Sg_request *srp;
@@ -1082,27 +1082,32 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
                 result = get_user(val, ip);
                 if (result)
                         return result;
+                if (val & SG_SCSI_RESET_NO_ESCALATE) {
+                        val &= ~SG_SCSI_RESET_NO_ESCALATE;
+                        val2 = SCSI_TRY_RESET_NO_ESCALATE;
+                } else
+                        val2 = 0;
                 if (SG_SCSI_RESET_NOTHING == val)
                         return 0;
                 switch (val) {
                 case SG_SCSI_RESET_DEVICE:
-                        val = SCSI_TRY_RESET_DEVICE;
+                        val2 |= SCSI_TRY_RESET_DEVICE;
                         break;
                 case SG_SCSI_RESET_TARGET:
-                        val = SCSI_TRY_RESET_TARGET;
+                        val2 |= SCSI_TRY_RESET_TARGET;
                         break;
                 case SG_SCSI_RESET_BUS:
-                        val = SCSI_TRY_RESET_BUS;
+                        val2 |= SCSI_TRY_RESET_BUS;
                         break;
                 case SG_SCSI_RESET_HOST:
-                        val = SCSI_TRY_RESET_HOST;
+                        val2 |= SCSI_TRY_RESET_HOST;
                         break;
                 default:
                         return -EINVAL;
                 }
                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                         return -EACCES;
-                return (scsi_reset_provider(sdp->device, val) ==
+                return (scsi_reset_provider(sdp->device, val2) ==
                         SUCCESS) ? 0 : -EIO;
         case SCSI_IOCTL_SEND_COMMAND:
                 if (atomic_read(&sdp->detaching))
diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
index 06a8790893ef..49af14ad5288 100644
--- a/include/scsi/scsi_eh.h
+++ b/include/scsi/scsi_eh.h
@@ -62,11 +62,16 @@ extern void scsi_build_sense_buffer(int desc, u8 *buf, u8 key, u8 asc, u8 ascq);
 
 /*
  * Reset request from external source
+ * Note: if SCSI_TRY_RESET_DEVICE fails then it will escalate to
+ * SCSI_TRY_RESET_TARGET which if it fails will escalate to
+ * SCSI_TRY_RESET_BUS which if it fails will escalate to SCSI_TRY_RESET_HOST.
+ * To prevent escalation OR with SCSI_TRY_RESET_NO_ESCALATE.
  */
 #define SCSI_TRY_RESET_DEVICE   1
 #define SCSI_TRY_RESET_BUS      2
 #define SCSI_TRY_RESET_HOST     3
 #define SCSI_TRY_RESET_TARGET   4
+#define SCSI_TRY_RESET_NO_ESCALATE      0x100   /* OR-ed to prior defines */
 
 extern int scsi_reset_provider(struct scsi_device *, int);
 
diff --git a/include/scsi/sg.h b/include/scsi/sg.h
index 750e5db7c6bf..3afec7032448 100644
--- a/include/scsi/sg.h
+++ b/include/scsi/sg.h
@@ -164,12 +164,15 @@ typedef struct sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */
 
 /* Returns -EBUSY if occupied. 3rd argument pointer to int (see next) */
 #define SG_SCSI_RESET 0x2284
-/* Associated values that can be given to SG_SCSI_RESET follow */
+/* Associated values that can be given to SG_SCSI_RESET follow.
+ * SG_SCSI_RESET_NO_ESCALATE may be OR-ed to the _DEVICE, _TARGET, _BUS
+ * or _HOST reset value so only that action is attempted. */
 #define         SG_SCSI_RESET_NOTHING   0
 #define         SG_SCSI_RESET_DEVICE    1
 #define         SG_SCSI_RESET_BUS       2
 #define         SG_SCSI_RESET_HOST      3
 #define         SG_SCSI_RESET_TARGET    4
+#define         SG_SCSI_RESET_NO_ESCALATE       0x100
 
 /* synchronous SCSI command ioctl, (only in version 3 interface) */
 #define SG_IO 0x2285   /* similar effect as write() followed by read() */