[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 1c244832c6c8..b4912d1cee2a 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 59716ebeb10c..d09532162217 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 ead47c143ce0..4d3ebb1af490 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 137d065db3da..6961f78742ae 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 d3a6d15fb77a..f608d4a1d6da 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 61be22774e99..0e8267c1e915 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 be58a0b097c7..7c45d88a205b 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 3c4efa4ae543..014654792901 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 bff7f8c59856..99a3b33a3233 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 bcb0b870320c..3bfd9296bbfa 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 d80dba913a75..f4a202e8df26 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 f93c73c0ba53..22ef3716e786 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 19cce125124c..c9dd8392aab2 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 05163cefec12..8be3d76656fa 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 5ea1f986220c..880c78bff0e1 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 890f44fa0e1a..ff149ad6bc4e 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 db004a450732..4d15a62914e9 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 30819012898f..78d46a900bb5 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 a10a5c74b48d..0cc8868ea35d 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 e5be5fd4ef58..b6f99dfbb038 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 6483c62730b3..fc5c3a42b05a 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 a035001f4438..b12ad7c7c673 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 765c24d2bc38..4d59ae8491a4 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 24e32e446e76..6db77c00e3ee 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 d7ec921865c4..672c759ac24d 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 7470ff39ab22..651d09b08f2a 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 28161dc95e0d..7fed35372150 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 969b9387a0c3..3454a5714749 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 c94906abfee3..68c0d09ffe78 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 aba1e6d48066..3954ed2d7b51 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 d3f86646cb08..2e2b9fedffcc 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 1769f965eedf..1e874f1fb5c6 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 4560713ecb14..e1c7eebfe907 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 e3fab3a6aed7..72f6d8015358 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 1f6fd1680335..6325901e5093 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 e939f3813233..d39107b7669b 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 4bc5407f9695..662c00451be4 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 75eca6b22db5..f385dce8dfbe 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 b4304ae78527..c975c01b3a02 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"