IB/srp: Implement SRP_CRED_REQ and SRP_AER_REQ

This patch adds support for SRP_CRED_REQ to avoid a lockup by targets
that use that mechanism to return credits to the initiator. This
prevents a lockup observed in the field where we would never add the
credits from the SRP_CRED_REQ to our current count, and would therefore
never send another command to the target.

Minimal support for SRP_AER_REQ is also added, as these messages can
also be used to convey additional credits to the initiator.

Based upon extensive debugging and code by Bart Van Assche and a bug
report by Chris Worley.

Signed-off-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/include/scsi/srp.h b/include/scsi/srp.h
index ad178fa78f66..1ae84db4c9fb 100644
--- a/include/scsi/srp.h
+++ b/include/scsi/srp.h
@@ -239,4 +239,42 @@ struct srp_rsp {
         u8      data[0];
 } __attribute__((packed));
 
+struct srp_cred_req {
+        u8      opcode;
+        u8      sol_not;
+        u8      reserved[2];
+        __be32  req_lim_delta;
+        u64     tag;
+};
+
+struct srp_cred_rsp {
+        u8      opcode;
+        u8      reserved[7];
+        u64     tag;
+};
+
+/*
+ * The SRP spec defines the fixed portion of the AER_REQ structure to be
+ * 36 bytes, so it needs to be packed to avoid having it padded to 40 bytes
+ * on 64-bit architectures.
+ */
+struct srp_aer_req {
+        u8      opcode;
+        u8      sol_not;
+        u8      reserved[2];
+        __be32  req_lim_delta;
+        u64     tag;
+        u32     reserved2;
+        __be64  lun;
+        __be32  sense_data_len;
+        u32     reserved3;
+        u8      sense_data[0];
+} __attribute__((packed));
+
+struct srp_aer_rsp {
+        u8      opcode;
+        u8      reserved[7];
+        u64     tag;
+};
+
 #endif /* SCSI_SRP_H */