[SCSI] implement scsi_data_buffer

In preparation for bidi we abstract all IO members of scsi_cmnd,
that will need to duplicate, into a substructure.

- Group all IO members of scsi_cmnd into a scsi_data_buffer
  structure.
- Adjust accessors to new members.
- scsi_{alloc,free}_sgtable receive a scsi_data_buffer instead of
  scsi_cmnd. And work on it.
- Adjust scsi_init_io() and  scsi_release_buffers() for above
  change.
- Fix other parts of scsi_lib/scsi.c to members migration. Use
  accessors where appropriate.

- fix Documentation about scsi_cmnd in scsi_host.h

- scsi_error.c
  * Changed needed members of struct scsi_eh_save.
  * Careful considerations in scsi_eh_prep/restore_cmnd.

- sd.c and sr.c
  * sd and sr would adjust IO size to align on device's block
    size so code needs to change once we move to scsi_data_buff
    implementation.
  * Convert code to use scsi_for_each_sg
  * Use data accessors where appropriate.

- tgt: convert libsrp to use scsi_data_buffer

- isd200: This driver still bangs on scsi_cmnd IO members,
  so need changing

[jejb: rebased on top of sg_table patches fixed up conflicts
and used the synergy to eliminate use_sg and sg_count]

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

3 files changed, 27 insertions, 21 deletions

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 09d44f91dbdb..c6478bb6f963 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -11,6 +11,11 @@ struct request;
 struct Scsi_Host;
 struct scsi_device;
 
+struct scsi_data_buffer {
+        struct sg_table table;
+        unsigned length;
+        int resid;
+};
 
 /* embedded in scsi_cmnd */
 struct scsi_pointer {
@@ -61,15 +66,11 @@ struct scsi_cmnd {
         /* These elements define the operation we are about to perform */
 #define MAX_COMMAND_SIZE        16
         unsigned char cmnd[MAX_COMMAND_SIZE];
-        unsigned request_bufflen;       /* Actual request size */
 
         struct timer_list eh_timeout;   /* Used to time out the command. */
-        void *request_buffer;           /* Actual requested buffer */
 
         /* These elements define the operation we ultimately want to perform */
-        struct sg_table sg_table;
-        unsigned short use_sg;  /* Number of pieces of scatter-gather */
-
+        struct scsi_data_buffer sdb;
         unsigned underflow;     /* Return error if less than
                                    this amount is transferred */
 
@@ -79,10 +80,6 @@ struct scsi_cmnd {
                                    reconnects.   Probably == sector
                                    size */
 
-        int resid;              /* Number of bytes requested to be
-                                   transferred less actual number
-                                   transferred (0 if not supported) */
-
         struct request *request;        /* The command we are
                                            working on */
 
@@ -133,18 +130,29 @@ extern void scsi_release_buffers(struct scsi_cmnd *cmd);
 extern int scsi_dma_map(struct scsi_cmnd *cmd);
 extern void scsi_dma_unmap(struct scsi_cmnd *cmd);
 
-#define scsi_sg_count(cmd) ((cmd)->use_sg)
-#define scsi_sglist(cmd) ((cmd)->sg_table.sgl)
-#define scsi_bufflen(cmd) ((cmd)->request_bufflen)
+static inline unsigned scsi_sg_count(struct scsi_cmnd *cmd)
+{
+        return cmd->sdb.table.nents;
+}
+
+static inline struct scatterlist *scsi_sglist(struct scsi_cmnd *cmd)
+{
+        return cmd->sdb.table.sgl;
+}
+
+static inline unsigned scsi_bufflen(struct scsi_cmnd *cmd)
+{
+        return cmd->sdb.length;
+}
 
 static inline void scsi_set_resid(struct scsi_cmnd *cmd, int resid)
 {
-        cmd->resid = resid;
+        cmd->sdb.resid = resid;
 }
 
 static inline int scsi_get_resid(struct scsi_cmnd *cmd)
 {
-        return cmd->resid;
+        return cmd->sdb.resid;
 }
 
 #define scsi_for_each_sg(cmd, sg, nseg, __i)                    \
diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
index d21b8913ceb3..1e08be1466ee 100644
--- a/include/scsi/scsi_eh.h
+++ b/include/scsi/scsi_eh.h
@@ -68,16 +68,14 @@ extern int scsi_get_sense_info_fld(const u8 * sense_buffer, int sb_len,
 extern int scsi_reset_provider(struct scsi_device *, int);
 
 struct scsi_eh_save {
+        /* saved state */
         int result;
         enum dma_data_direction data_direction;
         unsigned char cmd_len;
         unsigned char cmnd[MAX_COMMAND_SIZE];
+        struct scsi_data_buffer sdb;
 
-        void *buffer;
-        unsigned bufflen;
-        unsigned short use_sg;
-        int resid;
-
+        /* new command support */
         struct scatterlist sense_sgl;
 };
 
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 0fd4746ee39d..cb2bcab41dfb 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -136,9 +136,9 @@ struct scsi_host_template {
          * the done callback is invoked.
          *
          * This is called to inform the LLD to transfer
-         * cmd->request_bufflen bytes. The cmd->use_sg speciefies the
+         * scsi_bufflen(cmd) bytes. scsi_sg_count(cmd) speciefies the
          * number of scatterlist entried in the command and
-         * cmd->request_buffer contains the scatterlist.
+         * scsi_sglist(cmd) returns the scatterlist.
          *
          * return values: see queuecommand
          *