2 files changed, 19 insertions, 13 deletions

diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 702fcfeb37f1..0f55f5b24896 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -11,6 +11,25 @@
 #include <linux/types.h>
 
 /*
+ * 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.  We could define this
+ * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
+ * minimum value is 32
+ */
+#define SCSI_MAX_SG_SEGMENTS    128
+
+/*
+ * 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.
+ */
+#ifdef ARCH_HAS_SG_CHAIN
+#define SCSI_MAX_SG_CHAIN_SEGMENTS      2048
+#else
+#define SCSI_MAX_SG_CHAIN_SEGMENTS      SCSI_MAX_SG_SEGMENTS
+#endif
+
+/*
  *      SCSI command lengths
  */
 
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index cb2bcab41dfb..5c58d594126a 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -39,9 +39,6 @@ struct blk_queue_tags;
 #define DISABLE_CLUSTERING 0
 #define ENABLE_CLUSTERING 1
 
-#define DISABLE_SG_CHAINING 0
-#define ENABLE_SG_CHAINING 1
-
 enum scsi_eh_timer_return {
         EH_NOT_HANDLED,
         EH_HANDLED,
@@ -446,15 +443,6 @@ struct scsi_host_template {
         unsigned ordered_tag:1;
 
         /*
-         * true if the low-level driver can support sg chaining. this
-         * will be removed eventually when all the drivers are
-         * converted to support sg chaining.
-         *
-         * Status: OBSOLETE
-         */
-        unsigned use_sg_chaining:1;
-
-        /*
          * Countdown for host blocking with no commands outstanding
          */
         unsigned int max_host_blocked;
@@ -598,7 +586,6 @@ struct Scsi_Host {
         unsigned unchecked_isa_dma:1;
         unsigned use_clustering:1;
         unsigned use_blk_tcq:1;
-        unsigned use_sg_chaining:1;
 
         /*
          * Host has requested that no further requests come through for the