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Commit f29841e0 authored by Tejun Heo's avatar Tejun Heo Committed by Jeff Garzik
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[PATCH] libata: implement ata_scsi_timed_out() 



Implement ata_scsi_timed_out(), to be used as
scsi_host_template->eh_timed_out callback for all libata drivers.
Without this function, the following race exists.

If a qc completes after SCSI timer expires but before libata EH kicks
in, the qc gets completed but the scsicmd still gets passed to libata
EH resulting in ->eng_timeout invocation with NULL qc, which none is
handling properly.

This patch makes sure that scmd and qc share the same lifetime.
Original idea from Jeff Garzik <jgarzik@pobox.com>.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@pobox.com>
parent 341963b9

drivers/scsi/libata-core.c

+1 −0
Original line number Diff line number Diff line
@@ -4913,6 +4913,7 @@ EXPORT_SYMBOL_GPL(ata_ratelimit); 
EXPORT_SYMBOL_GPL(ata_busy_sleep);

EXPORT_SYMBOL_GPL(ata_scsi_ioctl);

EXPORT_SYMBOL_GPL(ata_scsi_queuecmd);

EXPORT_SYMBOL_GPL(ata_scsi_timed_out);

EXPORT_SYMBOL_GPL(ata_scsi_error);

EXPORT_SYMBOL_GPL(ata_scsi_slave_config);

EXPORT_SYMBOL_GPL(ata_scsi_release);

drivers/scsi/libata-scsi.c

+41 −0
Original line number Diff line number Diff line
@@ -716,6 +716,47 @@ int ata_scsi_slave_config(struct scsi_device *sdev) 
	return 0;	/* scsi layer doesn't check return value, sigh */

}



/**

 *	ata_scsi_timed_out - SCSI layer time out callback

 *	@cmd: timed out SCSI command

 *

 *	Handles SCSI layer timeout.  We race with normal completion of

 *	the qc for @cmd.  If the qc is already gone, we lose and let

 *	the scsi command finish (EH_HANDLED).  Otherwise, the qc has

 *	timed out and EH should be invoked.  Prevent ata_qc_complete()

 *	from finishing it by setting EH_SCHEDULED and return

 *	EH_NOT_HANDLED.

 *

 *	LOCKING:

 *	Called from timer context

 *

 *	RETURNS:

 *	EH_HANDLED or EH_NOT_HANDLED

 */

enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd)

{

	struct Scsi_Host *host = cmd->device->host;

	struct ata_port *ap = (struct ata_port *) &host->hostdata[0];

	unsigned long flags;

	struct ata_queued_cmd *qc;

	enum scsi_eh_timer_return ret = EH_HANDLED;



	DPRINTK("ENTER\n");



	spin_lock_irqsave(&ap->host_set->lock, flags);

	qc = ata_qc_from_tag(ap, ap->active_tag);

	if (qc) {

		assert(qc->scsicmd == cmd);

		qc->flags |= ATA_QCFLAG_EH_SCHEDULED;

		qc->err_mask |= AC_ERR_TIMEOUT;

		ret = EH_NOT_HANDLED;

	}

	spin_unlock_irqrestore(&ap->host_set->lock, flags);



	DPRINTK("EXIT, ret=%d\n", ret);

	return ret;

}



/**

 *	ata_scsi_error - SCSI layer error handler callback

 *	@host: SCSI host on which error occurred

include/linux/libata.h

+1 −0
Original line number Diff line number Diff line
@@ -509,6 +509,7 @@ extern void ata_host_set_remove(struct ata_host_set *host_set); 
extern int ata_scsi_detect(struct scsi_host_template *sht);

extern int ata_scsi_ioctl(struct scsi_device *dev, int cmd, void __user *arg);

extern int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *));

extern enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd);

extern int ata_scsi_error(struct Scsi_Host *host);

extern void ata_eh_qc_complete(struct ata_queued_cmd *qc);

extern void ata_eh_qc_retry(struct ata_queued_cmd *qc);