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Commit 832889f5 authored by Bart Van Assche's avatar Bart Van Assche Committed by Martin K. Petersen
Browse files

scsi: Improve requeuing behavior 



Requests are unprepared and reprepared when being requeued.  Avoid that
requeuing resets .jiffies_at_alloc and .retries by initializing these
two member variables from inside scsi_initialize_rq() and by preserving
both member variables when preparing a request. This patch affects the
requeuing behavior of both the legacy scsi and the scsi-mq code paths.

Reported-by: default avatarBrian King <brking@linux.vnet.ibm.com>
References: https://lkml.org/lkml/2017/8/18/923

 ("Re: [BUG][bisected 270065e] linux-next fails to boot on powerpc")
Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Brian King <brking@linux.vnet.ibm.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 64104f70

drivers/scsi/scsi_lib.c

+13 −2
Original line number Diff line number Diff line
@@ -1112,9 +1112,13 @@ int scsi_init_io(struct scsi_cmnd *cmd) 
EXPORT_SYMBOL(scsi_init_io);



/**

 * scsi_initialize_rq - initialize struct scsi_cmnd.req

 * scsi_initialize_rq - initialize struct scsi_cmnd partially

 * @rq: Request associated with the SCSI command to be initialized.

 *

 * This function initializes the members of struct scsi_cmnd that must be

 * initialized before request processing starts and that won't be

 * reinitialized if a SCSI command is requeued.

 *

 * Called from inside blk_get_request() for pass-through requests and from

 * inside scsi_init_command() for filesystem requests.

 */
@@ -1123,6 +1127,8 @@ void scsi_initialize_rq(struct request *rq) 
	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);



	scsi_req_init(&cmd->req);

	cmd->jiffies_at_alloc = jiffies;

	cmd->retries = 0;

}

EXPORT_SYMBOL(scsi_initialize_rq);
@@ -1162,12 +1168,16 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd) 
	void *prot = cmd->prot_sdb;

	struct request *rq = blk_mq_rq_from_pdu(cmd);

	unsigned int flags = cmd->flags & SCMD_PRESERVED_FLAGS;

	unsigned long jiffies_at_alloc;

	int retries;



	if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) {

		flags |= SCMD_INITIALIZED;

		scsi_initialize_rq(rq);

	}



	jiffies_at_alloc = cmd->jiffies_at_alloc;

	retries = cmd->retries;

	/* zero out the cmd, except for the embedded scsi_request */

	memset((char *)cmd + sizeof(cmd->req), 0,

		sizeof(*cmd) - sizeof(cmd->req) + dev->host->hostt->cmd_size);
@@ -1177,7 +1187,8 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd) 
	cmd->prot_sdb = prot;

	cmd->flags = flags;

	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);

	cmd->jiffies_at_alloc = jiffies;

	cmd->jiffies_at_alloc = jiffies_at_alloc;

	cmd->retries = retries;



	scsi_add_cmd_to_list(cmd);

}