[SCSI] sd/scsi_lib simplify sd_rw_intr and scsi_io_completion

This patch simplifies "good_bytes" computation in sd_rw_intr().
sd: "good_bytes" computation is always done in terms of the resolution
of the device's medium, since after that it is the number of good bytes
we pass around and other layers/contexts (as opposed ot sd) can translate
that to their own resolution (block layer:512).  It also makes
scsi_io_completion() processing more straightforward, eliminating the
3rd argument to the function.

It also fixes a couple of bugs like not checking return value,
using "break" instead of "return;", etc.

I've been running with this patch for some time now on a
test (do-it-all) system.

Signed-off-by: Luben Tuikov <ltuikov@yahoo.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 42 insertions, 66 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3d04a9f386ac..4c4add53d69b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -855,8 +855,7 @@ static void scsi_release_buffers(struct scsi_cmnd *cmd)
  *              b) We can just use scsi_requeue_command() here.  This would
  *                 be used if we just wanted to retry, for example.
  */
-void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
-                        unsigned int block_bytes)
+void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 {
         int result = cmd->result;
         int this_count = cmd->bufflen;
@@ -921,87 +920,72 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
          * Next deal with any sectors which we were able to correctly
          * handle.
          */
-        if (good_bytes >= 0) {
-                SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
+        if (good_bytes > 0) {
+                SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, "
+                                              "%d bytes done.\n",
                                               req->nr_sectors, good_bytes));
                 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
 
                 if (clear_errors)
                         req->errors = 0;
-                /*
-                 * If multiple sectors are requested in one buffer, then
-                 * they will have been finished off by the first command.
-                 * If not, then we have a multi-buffer command.
-                 *
-                 * If block_bytes != 0, it means we had a medium error
-                 * of some sort, and that we want to mark some number of
-                 * sectors as not uptodate.  Thus we want to inhibit
-                 * requeueing right here - we will requeue down below
-                 * when we handle the bad sectors.
-                 */
 
-                /*
-                 * If the command completed without error, then either
-                 * finish off the rest of the command, or start a new one.
+                /* A number of bytes were successfully read.  If there
+                 * is leftovers and there is some kind of error
+                 * (result != 0), retry the rest.
                  */
-                if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
+                if (scsi_end_request(cmd, 1, good_bytes, !!result) == NULL)
                         return;
         }
-        /*
-         * Now, if we were good little boys and girls, Santa left us a request
-         * sense buffer.  We can extract information from this, so we
-         * can choose a block to remap, etc.
+
+        /* good_bytes = 0, or (inclusive) there were leftovers and
+         * result = 0, so scsi_end_request couldn't retry.
          */
         if (sense_valid && !sense_deferred) {
                 switch (sshdr.sense_key) {
                 case UNIT_ATTENTION:
                         if (cmd->device->removable) {
-                                /* detected disc change.  set a bit 
+                                /* Detected disc change.  Set a bit
                                  * and quietly refuse further access.
                                  */
                                 cmd->device->changed = 1;
-                                scsi_end_request(cmd, 0,
-                                                this_count, 1);
+                                scsi_end_request(cmd, 0, this_count, 1);
                                 return;
                         } else {
-                                /*
-                                * Must have been a power glitch, or a
-                                * bus reset.  Could not have been a
-                                * media change, so we just retry the
-                                * request and see what happens.  
-                                */
+                                /* Must have been a power glitch, or a
+                                 * bus reset.  Could not have been a
+                                 * media change, so we just retry the
+                                 * request and see what happens.
+                                 */
                                 scsi_requeue_command(q, cmd);
                                 return;
                         }
                         break;
                 case ILLEGAL_REQUEST:
-                        /*
-                        * If we had an ILLEGAL REQUEST returned, then we may
-                        * have performed an unsupported command.  The only
-                        * thing this should be would be a ten byte read where
-                        * only a six byte read was supported.  Also, on a
-                        * system where READ CAPACITY failed, we may have read
-                        * past the end of the disk.
-                        */
+                        /* If we had an ILLEGAL REQUEST returned, then
+                         * we may have performed an unsupported
+                         * command.  The only thing this should be
+                         * would be a ten byte read where only a six
+                         * byte read was supported.  Also, on a system
+                         * where READ CAPACITY failed, we may have
+                         * read past the end of the disk.
+                         */
                         if ((cmd->device->use_10_for_rw &&
                             sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
                             (cmd->cmnd[0] == READ_10 ||
                              cmd->cmnd[0] == WRITE_10)) {
                                 cmd->device->use_10_for_rw = 0;
-                                /*
-                                 * This will cause a retry with a 6-byte
-                                 * command.
+                                /* This will cause a retry with a
+                                 * 6-byte command.
                                  */
                                 scsi_requeue_command(q, cmd);
-                                result = 0;
+                                return;
                         } else {
                                 scsi_end_request(cmd, 0, this_count, 1);
                                 return;
                         }
                         break;
                 case NOT_READY:
-                        /*
-                         * If the device is in the process of becoming
+                        /* If the device is in the process of becoming
                          * ready, or has a temporary blockage, retry.
                          */
                         if (sshdr.asc == 0x04) {
@@ -1021,7 +1005,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
                         }
                         if (!(req->flags & REQ_QUIET)) {
                                 scmd_printk(KERN_INFO, cmd,
-                                           "Device not ready: ");
+                                            "Device not ready: ");
                                 scsi_print_sense_hdr("", &sshdr);
                         }
                         scsi_end_request(cmd, 0, this_count, 1);
@@ -1029,21 +1013,21 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
                 case VOLUME_OVERFLOW:
                         if (!(req->flags & REQ_QUIET)) {
                                 scmd_printk(KERN_INFO, cmd,
-                                           "Volume overflow, CDB: ");
+                                            "Volume overflow, CDB: ");
                                 __scsi_print_command(cmd->data_cmnd);
                                 scsi_print_sense("", cmd);
                         }
-                        scsi_end_request(cmd, 0, block_bytes, 1);
+                        /* See SSC3rXX or current. */
+                        scsi_end_request(cmd, 0, this_count, 1);
                         return;
                 default:
                         break;
                 }
-        }                       /* driver byte != 0 */
+        }
         if (host_byte(result) == DID_RESET) {
-                /*
-                 * Third party bus reset or reset for error
-                 * recovery reasons.  Just retry the request
-                 * and see what happens.  
+                /* Third party bus reset or reset for error recovery
+                 * reasons.  Just retry the request and see what
+                 * happens.
                  */
                 scsi_requeue_command(q, cmd);
                 return;
@@ -1051,21 +1035,13 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
         if (result) {
                 if (!(req->flags & REQ_QUIET)) {
                         scmd_printk(KERN_INFO, cmd,
-                                   "SCSI error: return code = 0x%x\n", result);
-
+                                    "SCSI error: return code = 0x%08x\n",
+                                    result);
                         if (driver_byte(result) & DRIVER_SENSE)
                                 scsi_print_sense("", cmd);
                 }
-                /*
-                 * Mark a single buffer as not uptodate.  Queue the remainder.
-                 * We sometimes get this cruft in the event that a medium error
-                 * isn't properly reported.
-                 */
-                block_bytes = req->hard_cur_sectors << 9;
-                if (!block_bytes)
-                        block_bytes = req->data_len;
-                scsi_end_request(cmd, 0, block_bytes, 1);
         }
+        scsi_end_request(cmd, 0, this_count, !result);
 }
 EXPORT_SYMBOL(scsi_io_completion);
 
@@ -1169,7 +1145,7 @@ static void scsi_blk_pc_done(struct scsi_cmnd *cmd)
          * successfully. Since this is a REQ_BLOCK_PC command the
          * caller should check the request's errors value
          */
-        scsi_io_completion(cmd, cmd->bufflen, 0);
+        scsi_io_completion(cmd, cmd->bufflen);
 }
 
 static void scsi_setup_blk_pc_cmnd(struct scsi_cmnd *cmd)