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[PATCH] libata: implement ata_scsi_timed_out()

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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: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
This commit is contained in:
Tejun Heo 2006-02-10 15:10:48 +09:00 committed by Jeff Garzik
parent 341963b909
commit f29841e08f
3 changed files with 43 additions and 0 deletions
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1
drivers/scsi/libata-core.c
View file

@ -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);

41
drivers/scsi/libata-scsi.c
View file

@ -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

1
include/linux/libata.h
View file

@ -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);