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-rw-r--r--include/scsi/scsi.h19
-rw-r--r--include/scsi/scsi_host.h13
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- * Status: OBSOLETE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