Commit 71bada34 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Martin K. Petersen
Browse files

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: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarJohn Garry <john.garry@huawei.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent c49ff72c

drivers/scsi/scsi_lib.c

+28 −32
Original line number Diff line number Diff line
@@ -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);