scsi: core: Don't memset() the entire scsi_cmnd in scsi_init_command()

Replace the big fat memset that requires saving and restoring various
fields with just initializing those fields that need initialization.

All the clearing to 0 is moved to scsi_prepare_cmd() as scsi_ioctl_reset()
alreadly uses kzalloc() to allocate a pre-zeroed command.

This is still conservative and can probably be optimized further.

Link: https://lore.kernel.org/r/20220224175552.988286-3-hch@lst.de
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index a1c18ba5e8d38ee2206ba1e503b07cbdcdfd7a0d..572ffc3abe4433dd4bebf8bcfac9b1bb3c497b0c 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1163,45 +1163,16 @@ static void scsi_cleanup_rq(struct request *rq)
 /* Called before a request is prepared. See also scsi_mq_prep_fn(). */
 void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 {
-       void *buf = cmd->sense_buffer;
-       void *prot = cmd->prot_sdb;
        struct request *rq = scsi_cmd_to_rq(cmd);
-       unsigned int flags = cmd->flags & SCMD_PRESERVED_FLAGS;
-       unsigned long jiffies_at_alloc;
-       int retries, to_clear;
-       bool in_flight;
-       int budget_token = cmd->budget_token;
-
-       if (!blk_rq_is_passthrough(rq) && !(flags & SCMD_INITIALIZED)) {
-               flags |= SCMD_INITIALIZED;
+
+       if (!blk_rq_is_passthrough(rq) && !(cmd->flags & SCMD_INITIALIZED)) {
+               cmd->flags |= SCMD_INITIALIZED;
                scsi_initialize_rq(rq);
        }
 
-       jiffies_at_alloc = cmd->jiffies_at_alloc;
-       retries = cmd->retries;
-       in_flight = test_bit(SCMD_STATE_INFLIGHT, &cmd->state);
-       /*
-        * Zero out the cmd, except for the embedded scsi_request. Only clear
-        * the driver-private command data if the LLD does not supply a
-        * function to initialize that data.
-        */
-       to_clear = sizeof(*cmd) - sizeof(cmd->req);
-       if (!dev->host->hostt->init_cmd_priv)
-               to_clear += dev->host->hostt->cmd_size;
-       memset((char *)cmd + sizeof(cmd->req), 0, to_clear);
-
        cmd->device = dev;
-       cmd->sense_buffer = buf;
-       cmd->prot_sdb = prot;
-       cmd->flags = flags;
        INIT_LIST_HEAD(&cmd->eh_entry);
        INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
-       cmd->jiffies_at_alloc = jiffies_at_alloc;
-       cmd->retries = retries;
-       if (in_flight)
-               __set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
-       cmd->budget_token = budget_token;
-
 }
 
 static blk_status_t scsi_setup_scsi_cmnd(struct scsi_device *sdev,
@@ -1586,10 +1557,35 @@ static blk_status_t scsi_prepare_cmd(struct request *req)
        struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
        struct scsi_device *sdev = req->q->queuedata;
        struct Scsi_Host *shost = sdev->host;
+       bool in_flight = test_bit(SCMD_STATE_INFLIGHT, &cmd->state);
        struct scatterlist *sg;
 
        scsi_init_command(sdev, cmd);
 
+       cmd->eh_eflags = 0;
+       cmd->allowed = 0;
+       cmd->prot_type = 0;
+       cmd->prot_flags = 0;
+       cmd->submitter = 0;
+       cmd->cmd_len = 0;
+       cmd->cmnd = NULL;
+       memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+       cmd->underflow = 0;
+       cmd->transfersize = 0;
+       cmd->host_scribble = NULL;
+       cmd->result = 0;
+       cmd->extra_len = 0;
+       cmd->state = 0;
+       if (in_flight)
+               __set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
+
+       /*
+        * Only clear the driver-private command data if the LLD does not supply
+        * a function to initialize that data.
+        */
+       if (!shost->hostt->init_cmd_priv)
+               memset(cmd + 1, 0, shost->hostt->cmd_size);
+
        cmd->prot_op = SCSI_PROT_NORMAL;
        if (blk_rq_bytes(req))
                cmd->sc_data_direction = rq_dma_dir(req);