Merge tag 'scsi-sg' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI scatter-gather list updates from James Bottomley:
 "This topic branch covers a fundamental change in how our sg lists are
  allocated to make mq more efficient by reducing the size of the
  preallocated sg list.

  This necessitates a large number of driver changes because the
  previous guarantee that if a driver specified SG_ALL as the size of
  its scatter list, it would get a non-chained list and didn't need to
  bother with scatterlist iterators is now broken and every driver
  *must* use scatterlist iterators.

  This was broken out as a separate topic because we need to convert all
  the drivers before pulling the trigger and unconverted drivers kept
  being found, necessitating a rebase"

* tag 'scsi-sg' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (21 commits)
  scsi: core: don't preallocate small SGL in case of NO_SG_CHAIN
  scsi: lib/sg_pool.c: clear 'first_chunk' in case of no preallocation
  scsi: core: avoid preallocating big SGL for data
  scsi: core: avoid preallocating big SGL for protection information
  scsi: lib/sg_pool.c: improve APIs for allocating sg pool
  scsi: esp: use sg helper to iterate over scatterlist
  scsi: NCR5380: use sg helper to iterate over scatterlist
  scsi: wd33c93: use sg helper to iterate over scatterlist
  scsi: ppa: use sg helper to iterate over scatterlist
  scsi: pcmcia: nsp_cs: use sg helper to iterate over scatterlist
  scsi: imm: use sg helper to iterate over scatterlist
  scsi: aha152x: use sg helper to iterate over scatterlist
  scsi: s390: zfcp_fc: use sg helper to iterate over scatterlist
  scsi: staging: unisys: visorhba: use sg helper to iterate over scatterlist
  scsi: usb: image: microtek: use sg helper to iterate over scatterlist
  scsi: pmcraid: use sg helper to iterate over scatterlist
  scsi: ipr: use sg helper to iterate over scatterlist
  scsi: mvumi: use sg helper to iterate over scatterlist
  scsi: lpfc: use sg helper to iterate over scatterlist
  scsi: advansys: use sg helper to iterate over scatterlist
  ...

1 files changed, 18 insertions, 23 deletions

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index d9fa9cf2fd8b..536426f25e86 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -149,12 +149,10 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
 
 	if (scsi_bufflen(cmd)) {
 		cmd->SCp.buffer = scsi_sglist(cmd);
-		cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1;
 		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
 		cmd->SCp.this_residual = cmd->SCp.buffer->length;
 	} else {
 		cmd->SCp.buffer = NULL;
-		cmd->SCp.buffers_residual = 0;
 		cmd->SCp.ptr = NULL;
 		cmd->SCp.this_residual = 0;
 	}
@@ -163,6 +161,17 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
 	cmd->SCp.Message = 0;
 }
 
+static inline void advance_sg_buffer(struct scsi_cmnd *cmd)
+{
+	struct scatterlist *s = cmd->SCp.buffer;
+
+	if (!cmd->SCp.this_residual && s && !sg_is_last(s)) {
+		cmd->SCp.buffer = sg_next(s);
+		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
+		cmd->SCp.this_residual = cmd->SCp.buffer->length;
+	}
+}
+
 /**
  * NCR5380_poll_politely2 - wait for two chip register values
  * @hostdata: host private data
@@ -1670,12 +1679,7 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance)
 			    sun3_dma_setup_done != cmd) {
 				int count;
 
-				if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
-					++cmd->SCp.buffer;
-					--cmd->SCp.buffers_residual;
-					cmd->SCp.this_residual = cmd->SCp.buffer->length;
-					cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-				}
+				advance_sg_buffer(cmd);
 
 				count = sun3scsi_dma_xfer_len(hostdata, cmd);
 
@@ -1725,15 +1729,11 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance)
 				 * scatter-gather list, move onto the next one.
 				 */
 
-				if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
-					++cmd->SCp.buffer;
-					--cmd->SCp.buffers_residual;
-					cmd->SCp.this_residual = cmd->SCp.buffer->length;
-					cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-					dsprintk(NDEBUG_INFORMATION, instance, "%d bytes and %d buffers left\n",
-					         cmd->SCp.this_residual,
-					         cmd->SCp.buffers_residual);
-				}
+				advance_sg_buffer(cmd);
+				dsprintk(NDEBUG_INFORMATION, instance,
+					"this residual %d, sg ents %d\n",
+					cmd->SCp.this_residual,
+					sg_nents(cmd->SCp.buffer));
 
 				/*
 				 * The preferred transfer method is going to be
@@ -2126,12 +2126,7 @@ static void NCR5380_reselect(struct Scsi_Host *instance)
 	if (sun3_dma_setup_done != tmp) {
 		int count;
 
-		if (!tmp->SCp.this_residual && tmp->SCp.buffers_residual) {
-			++tmp->SCp.buffer;
-			--tmp->SCp.buffers_residual;
-			tmp->SCp.this_residual = tmp->SCp.buffer->length;
-			tmp->SCp.ptr = sg_virt(tmp->SCp.buffer);
-		}
+		advance_sg_buffer(tmp);
 
 		count = sun3scsi_dma_xfer_len(hostdata, tmp);