return valid data buffer length in scsi_bufflen() API using RQF_SPECIAL_PAYLOAD

Regression due to commit f9d03f96b988002027d4b28ea1b7a24729a4c9b5
block: improve handling of the magic discard payload

<megaraid_sas> and <mpt3sas> HBA FW encounter FW fault in DMA operation while creating File system on SSDs.
Below CDB cause FW fault.
CDB: Write same(16) 93 08 00 00 00 00 00 00 00 00 00 00 80 00 00 00

Root cause is SCSI buffer length and DMA buffer length miss match for WRITE SAME command.

Fix - return valid data buffer length in scsi_bufflen() API using RQF_SPECIAL_PAYLOAD

---

index 9fc1aec..1f796fc 100644
@@ -180,7 +180,8 @@ static inline struct scatterlist *scsi_sglist(struct

scsi_cmnd *cmd)

static inline unsigned scsi_bufflen(struct scsi_cmnd *cmd) {
- return cmd->sdb.length;
+ return (cmd->request->rq_flags & RQF_SPECIAL_PAYLOAD) ?
+ cmd->request->special_vec.bv_len :
cmd->sdb.length;
}

static inline void scsi_set_resid(struct scsi_cmnd *cmd, int resid)

Hi Kashyap,

can you try 4.10-rc8? It has "scsi: use blk_rq_payload_bytes" which initializeѕ sdb->length to blk_rq_payload_bytes(), which should fix your issue.