5 files changed, 51 insertions, 6 deletions

diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index b7be95b5bd24..38f81188def0 100644
--- a/Documentation/scsi/st.txt
+++ b/Documentation/scsi/st.txt
@@ -2,7 +2,7 @@ This file contains brief information about the SCSI tape driver.
 The driver is currently maintained by Kai Mäkisara (email
 Kai.Makisara@kolumbus.fi)
 
-Last modified: Mon Mar  7 21:14:44 2005 by kai.makisara
+Last modified: Thu Feb 21 21:54:16 2008 by kai.makisara
 
 
 BASICS
@@ -372,6 +372,11 @@ MTSETDRVBUFFER
              MT_ST_SYSV sets the SYSV semantics (mode)
              MT_ST_NOWAIT enables immediate mode (i.e., don't wait for
                 the command to finish) for some commands (e.g., rewind)
+             MT_ST_SILI enables setting the SILI bit in SCSI commands when
+                reading in variable block mode to enhance performance when
+                reading blocks shorter than the byte count; set this only
+                if you are sure that the drive supports SILI and the HBA
+                correctly returns transfer residuals
              MT_ST_DEBUGGING debugging (global; debugging must be
                 compiled into the driver)
         MT_ST_SETBOOLEANS
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 0a52d9d2da2c..a4361a8c6ac6 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -17,7 +17,7 @@
    Last modified: 18-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Devfs support
  */
 
-static const char *verstr = "20080221";
+static const char *verstr = "20080224";
 
 #include <linux/module.h>
 
@@ -183,6 +183,7 @@ static int modes_defined;
 
 static struct st_buffer *new_tape_buffer(int, int, int);
 static int enlarge_buffer(struct st_buffer *, int, int);
+static void clear_buffer(struct st_buffer *);
 static void normalize_buffer(struct st_buffer *);
 static int append_to_buffer(const char __user *, struct st_buffer *, int);
 static int from_buffer(struct st_buffer *, char __user *, int);
@@ -442,6 +443,7 @@ static void st_sleep_done(void *data, char *sense, int result, int resid)
 
         memcpy(SRpnt->sense, sense, SCSI_SENSE_BUFFERSIZE);
         (STp->buffer)->cmdstat.midlevel_result = SRpnt->result = result;
+        (STp->buffer)->cmdstat.residual = resid;
         DEB( STp->write_pending = 0; )
 
         if (SRpnt->waiting)
@@ -1159,6 +1161,7 @@ static int st_open(struct inode *inode, struct file *filp)
                 goto err_out;
         }
 
+        (STp->buffer)->cleared = 0;
         (STp->buffer)->writing = 0;
         (STp->buffer)->syscall_result = 0;
 
@@ -1432,8 +1435,14 @@ static int setup_buffering(struct scsi_tape *STp, const char __user *buf,
                 if (STp->block_size)
                         bufsize = STp->block_size > st_fixed_buffer_size ?
                                 STp->block_size : st_fixed_buffer_size;
-                else
+                else {
                         bufsize = count;
+                        /* Make sure that data from previous user is not leaked even if
+                           HBA does not return correct residual */
+                        if (is_read && STp->sili && !STbp->cleared)
+                                clear_buffer(STbp);
+                }
+
                 if (bufsize > STbp->buffer_size &&
                     !enlarge_buffer(STbp, bufsize, STp->restr_dma)) {
                         printk(KERN_WARNING "%s: Can't allocate %d byte tape buffer.\n",
@@ -1783,6 +1792,8 @@ static long read_tape(struct scsi_tape *STp, long count,
         memset(cmd, 0, MAX_COMMAND_SIZE);
         cmd[0] = READ_6;
         cmd[1] = (STp->block_size != 0);
+        if (!cmd[1] && STp->sili)
+                cmd[1] |= 2;
         cmd[2] = blks >> 16;
         cmd[3] = blks >> 8;
         cmd[4] = blks;
@@ -1911,8 +1922,11 @@ static long read_tape(struct scsi_tape *STp, long count,
 
         }
         /* End of error handling */ 
-        else                    /* Read successful */
+        else {                  /* Read successful */
                 STbp->buffer_bytes = bytes;
+                if (STp->sili) /* In fixed block mode residual is always zero here */
+                        STbp->buffer_bytes -= STp->buffer->cmdstat.residual;
+        }
 
         if (STps->drv_block >= 0) {
                 if (STp->block_size == 0)
@@ -2090,7 +2104,8 @@ static void st_log_options(struct scsi_tape * STp, struct st_modedef * STm, char
                        name, STm->defaults_for_writes, STp->omit_blklims, STp->can_partitions,
                        STp->scsi2_logical);
                 printk(KERN_INFO
-                       "%s:    sysv: %d nowait: %d\n", name, STm->sysv, STp->immediate);
+                       "%s:    sysv: %d nowait: %d sili: %d\n", name, STm->sysv, STp->immediate,
+                        STp->sili);
                 printk(KERN_INFO "%s:    debugging: %d\n",
                        name, debugging);
         }
@@ -2133,6 +2148,7 @@ static int st_set_options(struct scsi_tape *STp, long options)
                 STp->scsi2_logical = (options & MT_ST_SCSI2LOGICAL) != 0;
                 STp->immediate = (options & MT_ST_NOWAIT) != 0;
                 STm->sysv = (options & MT_ST_SYSV) != 0;
+                STp->sili = (options & MT_ST_SILI) != 0;
                 DEB( debugging = (options & MT_ST_DEBUGGING) != 0;
                      st_log_options(STp, STm, name); )
         } else if (code == MT_ST_SETBOOLEANS || code == MT_ST_CLEARBOOLEANS) {
@@ -2164,6 +2180,8 @@ static int st_set_options(struct scsi_tape *STp, long options)
                         STp->immediate = value;
                 if ((options & MT_ST_SYSV) != 0)
                         STm->sysv = value;
+                if ((options & MT_ST_SILI) != 0)
+                        STp->sili = value;
                 DEB(
                 if ((options & MT_ST_DEBUGGING) != 0)
                         debugging = value;
@@ -3655,6 +3673,8 @@ static int enlarge_buffer(struct st_buffer * STbuffer, int new_size, int need_dm
                 STbuffer->frp_segs += 1;
                 got += b_size;
                 STbuffer->buffer_size = got;
+                if (STbuffer->cleared)
+                        memset(page_address(STbuffer->frp[segs].page), 0, b_size);
                 segs++;
         }
         STbuffer->b_data = page_address(STbuffer->frp[0].page);
@@ -3663,6 +3683,17 @@ static int enlarge_buffer(struct st_buffer * STbuffer, int new_size, int need_dm
 }
 
 
+/* Make sure that no data from previous user is in the internal buffer */
+static void clear_buffer(struct st_buffer * st_bp)
+{
+        int i;
+
+        for (i=0; i < st_bp->frp_segs; i++)
+                memset(page_address(st_bp->frp[i].page), 0, st_bp->frp[i].length);
+        st_bp->cleared = 1;
+}
+
+
 /* Release the extra buffer */
 static void normalize_buffer(struct st_buffer * STbuffer)
 {
@@ -3987,6 +4018,7 @@ static int st_probe(struct device *dev)
         tpnt->two_fm = ST_TWO_FM;
         tpnt->fast_mteom = ST_FAST_MTEOM;
         tpnt->scsi2_logical = ST_SCSI2LOGICAL;
+        tpnt->sili = ST_SILI;
         tpnt->immediate = ST_NOWAIT;
         tpnt->default_drvbuffer = 0xff;         /* No forced buffering */
         tpnt->partition = 0;
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index 5931726fcf93..b92712f95931 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -12,6 +12,7 @@ struct st_cmdstatus {
         int midlevel_result;
         struct scsi_sense_hdr sense_hdr;
         int have_sense;
+        int residual;
         u64 uremainder64;
         u8 flags;
         u8 remainder_valid;
@@ -34,6 +35,7 @@ struct st_request {
 struct st_buffer {
         unsigned char dma;      /* DMA-able buffer */
         unsigned char do_dio;   /* direct i/o set up? */
+        unsigned char cleared;  /* internal buffer cleared after open? */
         int buffer_size;
         int buffer_blocks;
         int buffer_bytes;
@@ -122,6 +124,7 @@ struct scsi_tape {
         unsigned char try_dio_now;              /* try direct i/o before next close? */
         unsigned char c_algo;                   /* compression algorithm */
         unsigned char pos_unknown;                      /* after reset position unknown */
+        unsigned char sili;                     /* use SILI when reading in variable b mode */
         int tape_type;
         int long_timeout;       /* timeout for commands known to take long time */
 
diff --git a/drivers/scsi/st_options.h b/drivers/scsi/st_options.h
index b6b5c9c37677..d2f947935554 100644
--- a/drivers/scsi/st_options.h
+++ b/drivers/scsi/st_options.h
@@ -3,7 +3,7 @@
 
    Copyright 1995-2003 Kai Makisara.
 
-   Last modified: Mon Apr  7 22:49:18 2003 by makisara
+   Last modified: Thu Feb 21 21:47:07 2008 by kai.makisara
 */
 
 #ifndef _ST_OPTIONS_H
@@ -94,6 +94,10 @@
    The default is BSD semantics. */
 #define ST_SYSV 0
 
+/* If ST_SILI is non-zero, the SILI bit is set when reading in variable block
+   mode and the block size is determined using the residual returned by the HBA. */
+#define ST_SILI 0
+
 /* Time to wait for the drive to become ready if blocking open */
 #define ST_BLOCK_SECONDS     120
 
diff --git a/include/linux/mtio.h b/include/linux/mtio.h
index 6f8d2d45a8fb..ef01d6aa5934 100644
--- a/include/linux/mtio.h
+++ b/include/linux/mtio.h
@@ -192,6 +192,7 @@ struct	mtpos {
 #define MT_ST_SCSI2LOGICAL      0x800
 #define MT_ST_SYSV              0x1000
 #define MT_ST_NOWAIT            0x2000
+#define MT_ST_SILI              0x4000
 
 /* The mode parameters to be controlled. Parameter chosen with bits 20-28 */
 #define MT_ST_CLEAR_DEFAULT     0xfffff