ide-scsi: sg chaining support

Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 18 insertions, 14 deletions

diff --git a/drivers/scsi/ide-scsi.c b/drivers/scsi/ide-scsi.c
index d81bb076a15a..d297f64cd432 100644
--- a/drivers/scsi/ide-scsi.c
+++ b/drivers/scsi/ide-scsi.c
@@ -70,6 +70,7 @@ typedef struct idescsi_pc_s {
         u8 *buffer;                             /* Data buffer */
         u8 *current_position;                   /* Pointer into the above buffer */
         struct scatterlist *sg;                 /* Scatter gather table */
+        struct scatterlist *last_sg;            /* Last sg element */
         int b_count;                            /* Bytes transferred from current entry */
         struct scsi_cmnd *scsi_cmd;             /* SCSI command */
         void (*done)(struct scsi_cmnd *);       /* Scsi completion routine */
@@ -173,12 +174,6 @@ static void idescsi_input_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsigne
         char *buf;
 
         while (bcount) {
-                if (pc->sg - scsi_sglist(pc->scsi_cmd) >
-                                                 scsi_sg_count(pc->scsi_cmd)) {
-                        printk (KERN_ERR "ide-scsi: scatter gather table too small, discarding data\n");
-                        idescsi_discard_data (drive, bcount);
-                        return;
-                }
                 count = min(pc->sg->length - pc->b_count, bcount);
                 if (PageHighMem(pc->sg->page)) {
                         unsigned long flags;
@@ -197,10 +192,17 @@ static void idescsi_input_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsigne
                 }
                 bcount -= count; pc->b_count += count;
                 if (pc->b_count == pc->sg->length) {
-                        pc->sg++;
+                        if (pc->sg == pc->last_sg)
+                                break;
+                        pc->sg = sg_next(pc->sg);
                         pc->b_count = 0;
                 }
         }
+
+        if (bcount) {
+                printk (KERN_ERR "ide-scsi: scatter gather table too small, discarding data\n");
+                idescsi_discard_data (drive, bcount);
+        }
 }
 
 static void idescsi_output_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsigned int bcount)
@@ -209,12 +211,6 @@ static void idescsi_output_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsign
         char *buf;
 
         while (bcount) {
-                if (pc->sg - scsi_sglist(pc->scsi_cmd) >
-                                                 scsi_sg_count(pc->scsi_cmd)) {
-                        printk (KERN_ERR "ide-scsi: scatter gather table too small, padding with zeros\n");
-                        idescsi_output_zeros (drive, bcount);
-                        return;
-                }
                 count = min(pc->sg->length - pc->b_count, bcount);
                 if (PageHighMem(pc->sg->page)) {
                         unsigned long flags;
@@ -233,10 +229,17 @@ static void idescsi_output_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsign
                 }
                 bcount -= count; pc->b_count += count;
                 if (pc->b_count == pc->sg->length) {
-                        pc->sg++;
+                        if (pc->sg == pc->last_sg)
+                                break;
+                        pc->sg = sg_next(pc->sg);
                         pc->b_count = 0;
                 }
         }
+
+        if (bcount) {
+                printk (KERN_ERR "ide-scsi: scatter gather table too small, padding with zeros\n");
+                idescsi_output_zeros (drive, bcount);
+        }
 }
 
 static void hexdump(u8 *x, int len)
@@ -804,6 +807,7 @@ static int idescsi_queue (struct scsi_cmnd *cmd,
         memcpy (pc->c, cmd->cmnd, cmd->cmd_len);
         pc->buffer = NULL;
         pc->sg = scsi_sglist(cmd);
+        pc->last_sg = sg_last(pc->sg, cmd->use_sg);
         pc->b_count = 0;
         pc->request_transfer = pc->buffer_size = scsi_bufflen(cmd);
         pc->scsi_cmd = cmd;