block/scsi: Provide a limit on the number of integrity segments

Some controllers have a hardware limit on the number of protection
information scatter-gather list segments they can handle.

Introduce a max_integrity_segments limit in the block layer and provide
a new scsi_host_template setting that allows HBA drivers to provide a
value suitable for the hardware.

Add support for honoring the integrity segment limit when merging both
bios and requests.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>

2 files changed, 13 insertions, 0 deletions

diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 8fcb6e0e9e72..d63533a4a59e 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -32,6 +32,12 @@ struct scsi_cmnd;
 #endif
 
 /*
+ * DIX-capable adapters effectively support infinite chaining for the
+ * protection information scatterlist
+ */
+#define SCSI_MAX_PROT_SG_SEGMENTS       0xFFFF
+
+/*
  * Special value for scanning to specify scanning or rescanning of all
  * possible channels, (target) ids, or luns on a given shost.
  */
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index b7bdecb7b76e..d0a6a845f204 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -388,6 +388,7 @@ struct scsi_host_template {
          * of scatter-gather.
          */
         unsigned short sg_tablesize;
+        unsigned short sg_prot_tablesize;
 
         /*
          * Set this if the host adapter has limitations beside segment count.
@@ -599,6 +600,7 @@ struct Scsi_Host {
         int can_queue;
         short cmd_per_lun;
         short unsigned int sg_tablesize;
+        short unsigned int sg_prot_tablesize;
         short unsigned int max_sectors;
         unsigned long dma_boundary;
         /* 
@@ -823,6 +825,11 @@ static inline unsigned int scsi_host_get_prot(struct Scsi_Host *shost)
         return shost->prot_capabilities;
 }
 
+static inline int scsi_host_prot_dma(struct Scsi_Host *shost)
+{
+        return shost->prot_capabilities >= SHOST_DIX_TYPE0_PROTECTION;
+}
+
 static inline unsigned int scsi_host_dif_capable(struct Scsi_Host *shost, unsigned int target_type)
 {
         static unsigned char cap[] = { 0,