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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: Brian 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: Bart 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: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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1 changed files with 13 additions and 2 deletions
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@ -1112,9 +1112,13 @@ int scsi_init_io(struct scsi_cmnd *cmd)
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EXPORT_SYMBOL(scsi_init_io);
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/**
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* scsi_initialize_rq - initialize struct scsi_cmnd.req
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* scsi_initialize_rq - initialize struct scsi_cmnd partially
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* @rq: Request associated with the SCSI command to be initialized.
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*
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* This function initializes the members of struct scsi_cmnd that must be
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* initialized before request processing starts and that won't be
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* reinitialized if a SCSI command is requeued.
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*
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* Called from inside blk_get_request() for pass-through requests and from
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* inside scsi_init_command() for filesystem requests.
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*/
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@ -1123,6 +1127,8 @@ void scsi_initialize_rq(struct request *rq)
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struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
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scsi_req_init(&cmd->req);
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cmd->jiffies_at_alloc = jiffies;
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cmd->retries = 0;
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}
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EXPORT_SYMBOL(scsi_initialize_rq);
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@ -1162,12 +1168,16 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
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void *prot = cmd->prot_sdb;
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struct request *rq = blk_mq_rq_from_pdu(cmd);
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unsigned int flags = cmd->flags & SCMD_PRESERVED_FLAGS;
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unsigned long jiffies_at_alloc;
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int retries;
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if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) {
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flags |= SCMD_INITIALIZED;
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scsi_initialize_rq(rq);
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}
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jiffies_at_alloc = cmd->jiffies_at_alloc;
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retries = cmd->retries;
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/* zero out the cmd, except for the embedded scsi_request */
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memset((char *)cmd + sizeof(cmd->req), 0,
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sizeof(*cmd) - sizeof(cmd->req) + dev->host->hostt->cmd_size);
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@ -1177,7 +1187,8 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
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cmd->prot_sdb = prot;
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cmd->flags = flags;
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INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
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cmd->jiffies_at_alloc = jiffies;
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cmd->jiffies_at_alloc = jiffies_at_alloc;
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cmd->retries = retries;
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scsi_add_cmd_to_list(cmd);
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}
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