[PATCH 02/11] libata: Convert to host_lock less w/ interrupts disabled internally

[PATCH 02/11] libata: Convert to host_lock less w/ interrupts disabled internally

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch changes ata_scsi_queuecmd_lck() to a host lock less
ata_scsi_queuecmd() that will disable interrupts internally using
ap->lock and drops the now legacy host_lock unlock.

Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
---
 drivers/ata/libata-scsi.c |   14 ++++----------
 1 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a007c36..9614758 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3173,25 +3173,22 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
  *	SCSI commands.  This creates the overall effect of
  *	ATA and ATAPI devices appearing as SCSI devices.
  *
- *	LOCKING:
- *	Releases scsi-layer-held lock, and obtains host lock.
- *
  *	RETURNS:
  *	Return value from __ata_scsi_queuecmd() if @cmd can be queued,
  *	0 otherwise.
  */
-static int ata_scsi_queuecmd_lck(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
+int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
 {
 	struct ata_port *ap;
 	struct ata_device *dev;
 	struct scsi_device *scsidev = cmd->device;
 	struct Scsi_Host *shost = scsidev->host;
+	unsigned long irq_flags;
 	int rc = 0;
 
 	ap = ata_shost_to_port(shost);
 
-	spin_unlock(shost->host_lock);
-	spin_lock(ap->lock);
+	spin_lock_irqsave(ap->lock, irq_flags);
 
 	ata_scsi_dump_cdb(ap, cmd);
 
@@ -3203,13 +3200,10 @@ static int ata_scsi_queuecmd_lck(struct scsi_cmnd *cmd, void (*done)(struct scsi
 		done(cmd);
 	}
 
-	spin_unlock(ap->lock);
-	spin_lock(shost->host_lock);
+	spin_unlock_irqrestore(ap->lock, irq_flags);
 	return rc;
 }
 
-DEF_SCSI_QCMD(ata_scsi_queuecmd)
-
 /**
  *	ata_scsi_simulate - simulate SCSI command on ATA device
  *	@dev: the target device
-- 
1.7.2.3

Re: [PATCH 02/11] libata: Convert to host_lock less w/ interrupts disabled internally

[Jeff Garzik]

On 11/11/2010 07:13 PM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger<nab@linux-iscsi.org>
>
> This patch changes ata_scsi_queuecmd_lck() to a host lock less
> ata_scsi_queuecmd() that will disable interrupts internally using
> ap->lock and drops the now legacy host_lock unlock.
>
> Signed-off-by: Nicholas A. Bellinger<nab@linux-iscsi.org>
> ---
>   drivers/ata/libata-scsi.c |   14 ++++----------
>   1 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index a007c36..9614758 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3173,25 +3173,22 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
>    *	SCSI commands.  This creates the overall effect of
>    *	ATA and ATAPI devices appearing as SCSI devices.
>    *
> - *	LOCKING:
> - *	Releases scsi-layer-held lock, and obtains host lock.
> - *

The code appears correct but the comment removal is not.

Locking has not disappeared, and the ATA host lock continues to be obtained.

Re: [PATCH 02/11] libata: Convert to host_lock less w/ interrupts disabled internally

[Nicholas A. Bellinger]

On Thu, 2010-11-11 at 22:47 -0500, Jeff Garzik wrote:
> On 11/11/2010 07:13 PM, Nicholas A. Bellinger wrote:
> > From: Nicholas Bellinger<nab@linux-iscsi.org>
> >
> > This patch changes ata_scsi_queuecmd_lck() to a host lock less
> > ata_scsi_queuecmd() that will disable interrupts internally using
> > ap->lock and drops the now legacy host_lock unlock.
> >
> > Signed-off-by: Nicholas A. Bellinger<nab@linux-iscsi.org>
> > ---
> >   drivers/ata/libata-scsi.c |   14 ++++----------
> >   1 files changed, 4 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> > index a007c36..9614758 100644
> > --- a/drivers/ata/libata-scsi.c
> > +++ b/drivers/ata/libata-scsi.c
> > @@ -3173,25 +3173,22 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
> >    *	SCSI commands.  This creates the overall effect of
> >    *	ATA and ATAPI devices appearing as SCSI devices.
> >    *
> > - *	LOCKING:
> > - *	Releases scsi-layer-held lock, and obtains host lock.
> > - *
> 
> The code appears correct but the comment removal is not.
> 
> Locking has not disappeared, and the ATA host lock continues to be obtained.
> 
> 

My apologies for not reading this comment throughly..  Reinstating in
lio-core-2.6.git/lock_less-LLDs-for-38

Thank you!

--nab