[SCSI] remove use_sg_chaining

With the sg table code, every SCSI driver is now either chain capable
or broken (or has sg_tablesize set so chaining is never activated), so
there's no need to have a check in the host template.

Also tidy up the code by moving the scatterlist size defines into the
SCSI includes and permit the last entry of the scatterlist pools not
to be a power of two.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

39 files changed, 18 insertions, 96 deletions

diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
index 1c244832c6c..b4912d1cee2 100644
--- a/drivers/scsi/3w-9xxx.c
+++ b/drivers/scsi/3w-9xxx.c
@@ -1990,7 +1990,6 @@ static struct scsi_host_template driver_template = {
         .max_sectors            = TW_MAX_SECTORS,
         .cmd_per_lun            = TW_MAX_CMDS_PER_LUN,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .shost_attrs            = twa_host_attrs,
         .emulated               = 1
 };
diff --git a/drivers/scsi/3w-xxxx.c b/drivers/scsi/3w-xxxx.c
index 59716ebeb10..d0953216221 100644
--- a/drivers/scsi/3w-xxxx.c
+++ b/drivers/scsi/3w-xxxx.c
@@ -2261,7 +2261,6 @@ static struct scsi_host_template driver_template = {
         .max_sectors            = TW_MAX_SECTORS,
         .cmd_per_lun            = TW_MAX_CMDS_PER_LUN,  
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .shost_attrs            = tw_host_attrs,
         .emulated               = 1
 };
diff --git a/drivers/scsi/BusLogic.c b/drivers/scsi/BusLogic.c
index ead47c143ce..4d3ebb1af49 100644
--- a/drivers/scsi/BusLogic.c
+++ b/drivers/scsi/BusLogic.c
@@ -3575,7 +3575,6 @@ static struct scsi_host_template Bus_Logic_template = {
         .unchecked_isa_dma = 1,
         .max_sectors = 128,
         .use_clustering = ENABLE_CLUSTERING,
-        .use_sg_chaining = ENABLE_SG_CHAINING,
 };
 
 /*
diff --git a/drivers/scsi/NCR53c406a.c b/drivers/scsi/NCR53c406a.c
index 137d065db3d..6961f78742a 100644
--- a/drivers/scsi/NCR53c406a.c
+++ b/drivers/scsi/NCR53c406a.c
@@ -1065,7 +1065,6 @@ static struct scsi_host_template driver_template =
      .cmd_per_lun               = 1                     /* commands per lun */, 
      .unchecked_isa_dma         = 1                     /* unchecked_isa_dma */,
      .use_clustering            = ENABLE_CLUSTERING,
-     .use_sg_chaining           = ENABLE_SG_CHAINING,
 };
 
 #include "scsi_module.c"
diff --git a/drivers/scsi/a100u2w.c b/drivers/scsi/a100u2w.c
index d3a6d15fb77..f608d4a1d6d 100644
--- a/drivers/scsi/a100u2w.c
+++ b/drivers/scsi/a100u2w.c
@@ -1071,7 +1071,6 @@ static struct scsi_host_template inia100_template = {
         .sg_tablesize           = SG_ALL,
         .cmd_per_lun            = 1,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 static int __devinit inia100_probe_one(struct pci_dev *pdev,
diff --git a/drivers/scsi/aacraid/linit.c b/drivers/scsi/aacraid/linit.c
index 61be22774e9..0e8267c1e91 100644
--- a/drivers/scsi/aacraid/linit.c
+++ b/drivers/scsi/aacraid/linit.c
@@ -1032,7 +1032,6 @@ static struct scsi_host_template aac_driver_template = {
         .cmd_per_lun                    = AAC_NUM_IO_FIB,
 #endif
         .use_clustering                 = ENABLE_CLUSTERING,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
         .emulated                       = 1,
 };
 
diff --git a/drivers/scsi/aha1740.c b/drivers/scsi/aha1740.c
index be58a0b097c..7c45d88a205 100644
--- a/drivers/scsi/aha1740.c
+++ b/drivers/scsi/aha1740.c
@@ -563,7 +563,6 @@ static struct scsi_host_template aha1740_template = {
         .sg_tablesize     = AHA1740_SCATTER,
         .cmd_per_lun      = AHA1740_CMDLUN,
         .use_clustering   = ENABLE_CLUSTERING,
-        .use_sg_chaining  = ENABLE_SG_CHAINING,
         .eh_abort_handler = aha1740_eh_abort_handler,
 };
 
diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.c b/drivers/scsi/aic7xxx/aic79xx_osm.c
index 3c4efa4ae54..01465479290 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.c
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.c
@@ -766,7 +766,6 @@ struct scsi_host_template aic79xx_driver_template = {
         .max_sectors            = 8192,
         .cmd_per_lun            = 2,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .slave_alloc            = ahd_linux_slave_alloc,
         .slave_configure        = ahd_linux_slave_configure,
         .target_alloc           = ahd_linux_target_alloc,
diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.c b/drivers/scsi/aic7xxx/aic7xxx_osm.c
index bff7f8c5985..99a3b33a323 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.c
@@ -747,7 +747,6 @@ struct scsi_host_template aic7xxx_driver_template = {
         .max_sectors            = 8192,
         .cmd_per_lun            = 2,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .slave_alloc            = ahc_linux_slave_alloc,
         .slave_configure        = ahc_linux_slave_configure,
         .target_alloc           = ahc_linux_target_alloc,
diff --git a/drivers/scsi/aic7xxx_old.c b/drivers/scsi/aic7xxx_old.c
index bcb0b870320..3bfd9296bbf 100644
--- a/drivers/scsi/aic7xxx_old.c
+++ b/drivers/scsi/aic7xxx_old.c
@@ -11141,7 +11141,6 @@ static struct scsi_host_template driver_template = {
         .max_sectors            = 2048,
         .cmd_per_lun            = 3,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 #include "scsi_module.c"
diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
index d80dba913a7..f4a202e8df2 100644
--- a/drivers/scsi/arcmsr/arcmsr_hba.c
+++ b/drivers/scsi/arcmsr/arcmsr_hba.c
@@ -122,7 +122,6 @@ static struct scsi_host_template arcmsr_scsi_host_template = {
         .max_sectors            = ARCMSR_MAX_XFER_SECTORS,
         .cmd_per_lun            = ARCMSR_MAX_CMD_PERLUN,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .shost_attrs            = arcmsr_host_attrs,
 };
 #ifdef CONFIG_SCSI_ARCMSR_AER
diff --git a/drivers/scsi/dc395x.c b/drivers/scsi/dc395x.c
index f93c73c0ba5..22ef3716e78 100644
--- a/drivers/scsi/dc395x.c
+++ b/drivers/scsi/dc395x.c
@@ -4763,7 +4763,6 @@ static struct scsi_host_template dc395x_driver_template = {
         .eh_bus_reset_handler   = dc395x_eh_bus_reset,
         .unchecked_isa_dma      = 0,
         .use_clustering         = DISABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 
diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index 19cce125124..c9dd8392aab 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -3340,7 +3340,6 @@ static struct scsi_host_template driver_template = {
         .this_id                = 7,
         .cmd_per_lun            = 1,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 #include "scsi_module.c"
 MODULE_LICENSE("GPL");
diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
index 05163cefec1..8be3d76656f 100644
--- a/drivers/scsi/eata.c
+++ b/drivers/scsi/eata.c
@@ -524,7 +524,6 @@ static struct scsi_host_template driver_template = {
         .this_id = 7,
         .unchecked_isa_dma = 1,
         .use_clustering = ENABLE_CLUSTERING,
-        .use_sg_chaining = ENABLE_SG_CHAINING,
 };
 
 #if !defined(__BIG_ENDIAN_BITFIELD) && !defined(__LITTLE_ENDIAN_BITFIELD)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 5ea1f986220..880c78bff0e 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -342,7 +342,6 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
         shost->use_clustering = sht->use_clustering;
         shost->ordered_tag = sht->ordered_tag;
         shost->active_mode = sht->supported_mode;
-        shost->use_sg_chaining = sht->use_sg_chaining;
 
         if (sht->supported_mode == MODE_UNKNOWN)
                 /* means we didn't set it ... default to INITIATOR */
diff --git a/drivers/scsi/hptiop.c b/drivers/scsi/hptiop.c
index 890f44fa0e1..ff149ad6bc4 100644
--- a/drivers/scsi/hptiop.c
+++ b/drivers/scsi/hptiop.c
@@ -906,7 +906,6 @@ static struct scsi_host_template driver_template = {
         .unchecked_isa_dma          = 0,
         .emulated                   = 0,
         .use_clustering             = ENABLE_CLUSTERING,
-        .use_sg_chaining            = ENABLE_SG_CHAINING,
         .proc_name                  = driver_name,
         .shost_attrs                = hptiop_attrs,
         .this_id                    = -1,
diff --git a/drivers/scsi/ibmmca.c b/drivers/scsi/ibmmca.c
index db004a45073..4d15a62914e 100644
--- a/drivers/scsi/ibmmca.c
+++ b/drivers/scsi/ibmmca.c
@@ -1501,7 +1501,6 @@ static struct scsi_host_template ibmmca_driver_template = {
           .sg_tablesize   = 16,
           .cmd_per_lun    = 1,
           .use_clustering = ENABLE_CLUSTERING,
-          .use_sg_chaining = ENABLE_SG_CHAINING,
 };
 
 static int ibmmca_probe(struct device *dev)
diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 30819012898..78d46a900bb 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -1600,7 +1600,6 @@ static struct scsi_host_template driver_template = {
         .this_id = -1,
         .sg_tablesize = SG_ALL,
         .use_clustering = ENABLE_CLUSTERING,
-        .use_sg_chaining = ENABLE_SG_CHAINING,
         .shost_attrs = ibmvscsi_attrs,
 };
 
diff --git a/drivers/scsi/initio.c b/drivers/scsi/initio.c
index a10a5c74b48..0cc8868ea35 100644
--- a/drivers/scsi/initio.c
+++ b/drivers/scsi/initio.c
@@ -2833,7 +2833,6 @@ static struct scsi_host_template initio_template = {
         .sg_tablesize           = SG_ALL,
         .cmd_per_lun            = 1,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 static int initio_probe_one(struct pci_dev *pdev,
diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index e5be5fd4ef5..b6f99dfbb03 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -1933,7 +1933,6 @@ static struct scsi_host_template iscsi_sht = {
         .eh_device_reset_handler= iscsi_eh_device_reset,
         .eh_host_reset_handler  = iscsi_eh_host_reset,
         .use_clustering         = DISABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .slave_configure        = iscsi_tcp_slave_configure,
         .proc_name              = "iscsi_tcp",
         .this_id                = -1,
diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index 6483c62730b..fc5c3a42b05 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/drivers/scsi/lpfc/lpfc_scsi.c
@@ -1459,7 +1459,6 @@ struct scsi_host_template lpfc_template = {
         .scan_finished          = lpfc_scan_finished,
         .this_id                = -1,
         .sg_tablesize           = LPFC_DEFAULT_SG_SEG_CNT,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .cmd_per_lun            = LPFC_CMD_PER_LUN,
         .use_clustering         = ENABLE_CLUSTERING,
         .shost_attrs            = lpfc_hba_attrs,
@@ -1482,7 +1481,6 @@ struct scsi_host_template lpfc_vport_template = {
         .sg_tablesize           = LPFC_DEFAULT_SG_SEG_CNT,
         .cmd_per_lun            = LPFC_CMD_PER_LUN,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .shost_attrs            = lpfc_vport_attrs,
         .max_sectors            = 0xFFFF,
 };
diff --git a/drivers/scsi/mac53c94.c b/drivers/scsi/mac53c94.c
index a035001f443..b12ad7c7c67 100644
--- a/drivers/scsi/mac53c94.c
+++ b/drivers/scsi/mac53c94.c
@@ -402,7 +402,6 @@ static struct scsi_host_template mac53c94_template = {
         .sg_tablesize   = SG_ALL,
         .cmd_per_lun    = 1,
         .use_clustering = DISABLE_CLUSTERING,
-        .use_sg_chaining = ENABLE_SG_CHAINING,
 };
 
 static int mac53c94_probe(struct macio_dev *mdev, const struct of_device_id *match)
diff --git a/drivers/scsi/megaraid.c b/drivers/scsi/megaraid.c
index 765c24d2bc3..4d59ae8491a 100644
--- a/drivers/scsi/megaraid.c
+++ b/drivers/scsi/megaraid.c
@@ -4490,7 +4490,6 @@ static struct scsi_host_template megaraid_template = {
         .sg_tablesize                   = MAX_SGLIST,
         .cmd_per_lun                    = DEF_CMD_PER_LUN,
         .use_clustering                 = ENABLE_CLUSTERING,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
         .eh_abort_handler               = megaraid_abort,
         .eh_device_reset_handler        = megaraid_reset,
         .eh_bus_reset_handler           = megaraid_reset,
diff --git a/drivers/scsi/megaraid/megaraid_mbox.c b/drivers/scsi/megaraid/megaraid_mbox.c
index 24e32e446e7..6db77c00e3e 100644
--- a/drivers/scsi/megaraid/megaraid_mbox.c
+++ b/drivers/scsi/megaraid/megaraid_mbox.c
@@ -361,7 +361,6 @@ static struct scsi_host_template megaraid_template_g = {
         .eh_host_reset_handler          = megaraid_reset_handler,
         .change_queue_depth             = megaraid_change_queue_depth,
         .use_clustering                 = ENABLE_CLUSTERING,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
         .sdev_attrs                     = megaraid_sdev_attrs,
         .shost_attrs                    = megaraid_shost_attrs,
 };
diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
index d7ec921865c..672c759ac24 100644
--- a/drivers/scsi/megaraid/megaraid_sas.c
+++ b/drivers/scsi/megaraid/megaraid_sas.c
@@ -1192,7 +1192,6 @@ static struct scsi_host_template megasas_template = {
         .eh_timed_out = megasas_reset_timer,
         .bios_param = megasas_bios_param,
         .use_clustering = ENABLE_CLUSTERING,
-        .use_sg_chaining = ENABLE_SG_CHAINING,
 };
 
 /**
diff --git a/drivers/scsi/mesh.c b/drivers/scsi/mesh.c
index 7470ff39ab2..651d09b08f2 100644
--- a/drivers/scsi/mesh.c
+++ b/drivers/scsi/mesh.c
@@ -1843,7 +1843,6 @@ static struct scsi_host_template mesh_template = {
         .sg_tablesize                   = SG_ALL,
         .cmd_per_lun                    = 2,
         .use_clustering                 = DISABLE_CLUSTERING,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
 };
 
 static int mesh_probe(struct macio_dev *mdev, const struct of_device_id *match)
diff --git a/drivers/scsi/nsp32.c b/drivers/scsi/nsp32.c
index 28161dc95e0..7fed3537215 100644
--- a/drivers/scsi/nsp32.c
+++ b/drivers/scsi/nsp32.c
@@ -281,7 +281,6 @@ static struct scsi_host_template nsp32_template = {
         .cmd_per_lun                    = 1,
         .this_id                        = NSP32_HOST_SCSIID,
         .use_clustering                 = DISABLE_CLUSTERING,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
         .eh_abort_handler               = nsp32_eh_abort,
         .eh_bus_reset_handler           = nsp32_eh_bus_reset,
         .eh_host_reset_handler          = nsp32_eh_host_reset,
diff --git a/drivers/scsi/pcmcia/sym53c500_cs.c b/drivers/scsi/pcmcia/sym53c500_cs.c
index 969b9387a0c..3454a571474 100644
--- a/drivers/scsi/pcmcia/sym53c500_cs.c
+++ b/drivers/scsi/pcmcia/sym53c500_cs.c
@@ -692,7 +692,6 @@ static struct scsi_host_template sym53c500_driver_template = {
      .sg_tablesize              = 32,
      .cmd_per_lun               = 1,
      .use_clustering            = ENABLE_CLUSTERING,
-     .use_sg_chaining           = ENABLE_SG_CHAINING,
      .shost_attrs               = SYM53C500_shost_attrs
 };
 
diff --git a/drivers/scsi/qla1280.c b/drivers/scsi/qla1280.c
index c94906abfee..68c0d09ffe7 100644
--- a/drivers/scsi/qla1280.c
+++ b/drivers/scsi/qla1280.c
@@ -4204,7 +4204,6 @@ static struct scsi_host_template qla1280_driver_template = {
         .sg_tablesize           = SG_ALL,
         .cmd_per_lun            = 1,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 
diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index aba1e6d4806..3954ed2d7b5 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -131,7 +131,6 @@ static struct scsi_host_template qla2x00_driver_template = {
         .this_id                = -1,
         .cmd_per_lun            = 3,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .sg_tablesize           = SG_ALL,
 
         /*
@@ -163,7 +162,6 @@ struct scsi_host_template qla24xx_driver_template = {
         .this_id                = -1,
         .cmd_per_lun            = 3,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .sg_tablesize           = SG_ALL,
 
         .max_sectors            = 0xFFFF,
diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
index d3f86646cb0..2e2b9fedffc 100644
--- a/drivers/scsi/qla4xxx/ql4_os.c
+++ b/drivers/scsi/qla4xxx/ql4_os.c
@@ -94,7 +94,6 @@ static struct scsi_host_template qla4xxx_driver_template = {
         .this_id                = -1,
         .cmd_per_lun            = 3,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .sg_tablesize           = SG_ALL,
 
         .max_sectors            = 0xFFFF,
diff --git a/drivers/scsi/qlogicfas.c b/drivers/scsi/qlogicfas.c
index 1769f965eed..1e874f1fb5c 100644
--- a/drivers/scsi/qlogicfas.c
+++ b/drivers/scsi/qlogicfas.c
@@ -197,7 +197,6 @@ static struct scsi_host_template qlogicfas_driver_template = {
         .sg_tablesize           = SG_ALL,
         .cmd_per_lun            = 1,
         .use_clustering         = DISABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 static __init int qlogicfas_init(void)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4560713ecb1..e1c7eebfe90 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bio.h>
+#include <linux/bitops.h>
 #include <linux/blkdev.h>
 #include <linux/completion.h>
 #include <linux/kernel.h>
@@ -34,13 +35,6 @@
 #define SG_MEMPOOL_NR           ARRAY_SIZE(scsi_sg_pools)
 #define SG_MEMPOOL_SIZE         2
 
-/*
- * The maximum number of SG segments that we will put inside a scatterlist
- * (unless chaining is used). Should ideally fit inside a single page, to
- * avoid a higher order allocation.
- */
-#define SCSI_MAX_SG_SEGMENTS    128
-
 struct scsi_host_sg_pool {
         size_t          size;
         char            *name;
@@ -48,19 +42,26 @@ struct scsi_host_sg_pool {
         mempool_t       *pool;
 };
 
-#define SP(x) { x, "sgpool-" #x }
+#define SP(x) { x, "sgpool-" __stringify(x) }
+#if (SCSI_MAX_SG_SEGMENTS < 32)
+#error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
+#endif
 static struct scsi_host_sg_pool scsi_sg_pools[] = {
         SP(8),
         SP(16),
-#if (SCSI_MAX_SG_SEGMENTS > 16)
-        SP(32),
 #if (SCSI_MAX_SG_SEGMENTS > 32)
-        SP(64),
+        SP(32),
 #if (SCSI_MAX_SG_SEGMENTS > 64)
+        SP(64),
+#if (SCSI_MAX_SG_SEGMENTS > 128)
         SP(128),
+#if (SCSI_MAX_SG_SEGMENTS > 256)
+#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
 #endif
 #endif
 #endif
+#endif
+        SP(SCSI_MAX_SG_SEGMENTS)
 };
 #undef SP
 
@@ -692,42 +693,16 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
         return NULL;
 }
 
-/*
- * Like SCSI_MAX_SG_SEGMENTS, but for archs that have sg chaining. This limit
- * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
- */
-#define SCSI_MAX_SG_CHAIN_SEGMENTS      2048
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
         unsigned int index;
 
-        switch (nents) {
-        case 1 ... 8:
+        BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
+
+        if (nents <= 8)
                 index = 0;
-                break;
-        case 9 ... 16:
-                index = 1;
-                break;
-#if (SCSI_MAX_SG_SEGMENTS > 16)
-        case 17 ... 32:
-                index = 2;
-                break;
-#if (SCSI_MAX_SG_SEGMENTS > 32)
-        case 33 ... 64:
-                index = 3;
-                break;
-#if (SCSI_MAX_SG_SEGMENTS > 64)
-        case 65 ... 128:
-                index = 4;
-                break;
-#endif
-#endif
-#endif
-        default:
-                printk(KERN_ERR "scsi: bad segment count=%d\n", nents);
-                BUG();
-        }
+        else
+                index = get_count_order(nents) - 3;
 
         return index;
 }
@@ -1603,20 +1578,7 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
          * this limit is imposed by hardware restrictions
          */
         blk_queue_max_hw_segments(q, shost->sg_tablesize);
-
-        /*
-         * In the future, sg chaining support will be mandatory and this
-         * ifdef can then go away. Right now we don't have all archs
-         * converted, so better keep it safe.
-         */
-#ifdef ARCH_HAS_SG_CHAIN
-        if (shost->use_sg_chaining)
-                blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
-        else
-                blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
-#else
-        blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
-#endif
+        blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
 
         blk_queue_max_sectors(q, shost->max_sectors);
         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
diff --git a/drivers/scsi/stex.c b/drivers/scsi/stex.c
index e3fab3a6aed..72f6d801535 100644
--- a/drivers/scsi/stex.c
+++ b/drivers/scsi/stex.c
@@ -1123,7 +1123,6 @@ static struct scsi_host_template driver_template = {
         .this_id                        = -1,
         .sg_tablesize                   = ST_MAX_SG,
         .cmd_per_lun                    = ST_CMD_PER_LUN,
-        .use_sg_chaining                = ENABLE_SG_CHAINING,
 };
 
 static int stex_set_dma_mask(struct pci_dev * pdev)
diff --git a/drivers/scsi/sym53c416.c b/drivers/scsi/sym53c416.c
index 1f6fd168033..6325901e509 100644
--- a/drivers/scsi/sym53c416.c
+++ b/drivers/scsi/sym53c416.c
@@ -840,6 +840,5 @@ static struct scsi_host_template driver_template = {
         .cmd_per_lun =          1,
         .unchecked_isa_dma =    1,
         .use_clustering =       ENABLE_CLUSTERING,
-        .use_sg_chaining =      ENABLE_SG_CHAINING,
 };
 #include "scsi_module.c"
diff --git a/drivers/scsi/sym53c8xx_2/sym_glue.c b/drivers/scsi/sym53c8xx_2/sym_glue.c
index e939f381323..d39107b7669 100644
--- a/drivers/scsi/sym53c8xx_2/sym_glue.c
+++ b/drivers/scsi/sym53c8xx_2/sym_glue.c
@@ -1681,7 +1681,6 @@ static struct scsi_host_template sym2_template = {
         .eh_host_reset_handler  = sym53c8xx_eh_host_reset_handler,
         .this_id                = 7,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .max_sectors            = 0xFFFF,
 #ifdef SYM_LINUX_PROC_INFO_SUPPORT
         .proc_info              = sym53c8xx_proc_info,
diff --git a/drivers/scsi/u14-34f.c b/drivers/scsi/u14-34f.c
index 4bc5407f969..662c00451be 100644
--- a/drivers/scsi/u14-34f.c
+++ b/drivers/scsi/u14-34f.c
@@ -451,7 +451,6 @@ static struct scsi_host_template driver_template = {
                 .this_id                 = 7,
                 .unchecked_isa_dma       = 1,
                 .use_clustering          = ENABLE_CLUSTERING,
-                .use_sg_chaining         = ENABLE_SG_CHAINING,
                 };
 
 #if !defined(__BIG_ENDIAN_BITFIELD) && !defined(__LITTLE_ENDIAN_BITFIELD)
diff --git a/drivers/scsi/ultrastor.c b/drivers/scsi/ultrastor.c
index 75eca6b22db..f385dce8dfb 100644
--- a/drivers/scsi/ultrastor.c
+++ b/drivers/scsi/ultrastor.c
@@ -1204,6 +1204,5 @@ static struct scsi_host_template driver_template = {
         .cmd_per_lun       = ULTRASTOR_MAX_CMDS_PER_LUN,
         .unchecked_isa_dma = 1,
         .use_clustering    = ENABLE_CLUSTERING,
-        .use_sg_chaining   = ENABLE_SG_CHAINING,
 };
 #include "scsi_module.c"
diff --git a/drivers/scsi/wd7000.c b/drivers/scsi/wd7000.c
index b4304ae7852..c975c01b3a0 100644
--- a/drivers/scsi/wd7000.c
+++ b/drivers/scsi/wd7000.c
@@ -1671,7 +1671,6 @@ static struct scsi_host_template driver_template = {
         .cmd_per_lun            = 1,
         .unchecked_isa_dma      = 1,
         .use_clustering         = ENABLE_CLUSTERING,
-        .use_sg_chaining        = ENABLE_SG_CHAINING,
 };
 
 #include "scsi_module.c"