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>

2 files changed, 9 insertions, 1 deletions

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() */