From bd81372065fa467e262150c70be885f47f9535df Mon Sep 17 00:00:00 2001 From: Lee Duncan Date: Tue, 15 May 2018 18:25:24 -0700 Subject: [PATCH] scsi: target: transport should handle st FM/EOM/ILI reads When a tape drive is exported via LIO using the pscsi module, a read that requests more bytes per block than the tape can supply returns an empty buffer. This is because the pscsi pass-through target module sees the "ILI" illegal length bit set and thinks there is no reason to return the data. This is a long-standing transport issue, since it assumes that no data need be returned under a check condition, which isn't always the case for tape. Add in a check for tape reads with the ILI, EOM, or FM bits set, with a sense code of NO_SENSE, treating such cases as if the read succeeded. The layered tape driver then "does the right thing" when it gets such a response. Signed-off-by: Bodo Stroesser Signed-off-by: Lee Duncan Reviewed-by: Hannes Reinecke Signed-off-by: Martin K. Petersen --- drivers/target/target_core_pscsi.c | 26 ++++++++++++++-- drivers/target/target_core_transport.c | 43 ++++++++++++++++++++++---- include/target/target_core_base.h | 1 + 3 files changed, 62 insertions(+), 8 deletions(-) diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c index 0d99b242e82e..f31215b1d009 100644 --- a/drivers/target/target_core_pscsi.c +++ b/drivers/target/target_core_pscsi.c @@ -689,8 +689,29 @@ static void pscsi_complete_cmd(struct se_cmd *cmd, u8 scsi_status, } after_mode_select: - if (scsi_status == SAM_STAT_CHECK_CONDITION) + if (scsi_status == SAM_STAT_CHECK_CONDITION) { transport_copy_sense_to_cmd(cmd, req_sense); + + /* + * check for TAPE device reads with + * FM/EOM/ILI set, so that we can get data + * back despite framework assumption that a + * check condition means there is no data + */ + if (sd->type == TYPE_TAPE && + cmd->data_direction == DMA_FROM_DEVICE) { + /* + * is sense data valid, fixed format, + * and have FM, EOM, or ILI set? + */ + if (req_sense[0] == 0xf0 && /* valid, fixed format */ + req_sense[2] & 0xe0 && /* FM, EOM, or ILI */ + (req_sense[2] & 0xf) == 0) { /* key==NO_SENSE */ + pr_debug("Tape FM/EOM/ILI status detected. Treat as normal read.\n"); + cmd->se_cmd_flags |= SCF_TREAT_READ_AS_NORMAL; + } + } + } } enum { @@ -1061,7 +1082,8 @@ static void pscsi_req_done(struct request *req, blk_status_t status) switch (host_byte(result)) { case DID_OK: - target_complete_cmd(cmd, scsi_status); + target_complete_cmd_with_length(cmd, scsi_status, + cmd->data_length - scsi_req(req)->resid_len); break; default: pr_debug("PSCSI Host Byte exception at cmd: %p CDB:" diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 3500aa5927f2..bde14f46ed5b 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -779,7 +779,9 @@ EXPORT_SYMBOL(target_complete_cmd); void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length) { - if (scsi_status == SAM_STAT_GOOD && length < cmd->data_length) { + if ((scsi_status == SAM_STAT_GOOD || + cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) && + length < cmd->data_length) { if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) { cmd->residual_count += cmd->data_length - length; } else { @@ -2084,12 +2086,24 @@ static void transport_complete_qf(struct se_cmd *cmd) goto queue_status; } - if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) + /* + * Check if we need to send a sense buffer from + * the struct se_cmd in question. We do NOT want + * to take this path of the IO has been marked as + * needing to be treated like a "normal read". This + * is the case if it's a tape read, and either the + * FM, EOM, or ILI bits are set, but there is no + * sense data. + */ + if (!(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) && + cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) goto queue_status; switch (cmd->data_direction) { case DMA_FROM_DEVICE: - if (cmd->scsi_status) + /* queue status if not treating this as a normal read */ + if (cmd->scsi_status && + !(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL)) goto queue_status; trace_target_cmd_complete(cmd); @@ -2194,9 +2208,15 @@ static void target_complete_ok_work(struct work_struct *work) /* * Check if we need to send a sense buffer from - * the struct se_cmd in question. + * the struct se_cmd in question. We do NOT want + * to take this path of the IO has been marked as + * needing to be treated like a "normal read". This + * is the case if it's a tape read, and either the + * FM, EOM, or ILI bits are set, but there is no + * sense data. */ - if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) { + if (!(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) && + cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) { WARN_ON(!cmd->scsi_status); ret = transport_send_check_condition_and_sense( cmd, 0, 1); @@ -2238,7 +2258,18 @@ static void target_complete_ok_work(struct work_struct *work) queue_rsp: switch (cmd->data_direction) { case DMA_FROM_DEVICE: - if (cmd->scsi_status) + /* + * if this is a READ-type IO, but SCSI status + * is set, then skip returning data and just + * return the status -- unless this IO is marked + * as needing to be treated as a normal read, + * in which case we want to go ahead and return + * the data. This happens, for example, for tape + * reads with the FM, EOM, or ILI bits set, with + * no sense data. + */ + if (cmd->scsi_status && + !(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL)) goto queue_status; atomic_long_add(cmd->data_length, diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 9f9f5902af38..922a39f45abc 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -143,6 +143,7 @@ enum se_cmd_flags_table { SCF_ACK_KREF = 0x00400000, SCF_USE_CPUID = 0x00800000, SCF_TASK_ATTR_SET = 0x01000000, + SCF_TREAT_READ_AS_NORMAL = 0x02000000, }; /*