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Date: Mon, 12 May 2008 22:32:39 +0200
From: "Jesper Juhl" <jesper.juhl@...il.com>
To: "James Bottomley" <James.Bottomley@...senpartnership.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
"Eric Youngdale" <eric@...ante.org>,
"David Miller" <davem@...emloft.net>,
"Mike Anderson" <andmike@...ibm.com>,
"Russell King" <rmk@....linux.org.uk>,
"Jesper Juhl" <jesper.juhl@...il.com>,
"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH][Resend] fewer pointer derefs in scsi_error
2008/4/27 Jesper Juhl <jesper.juhl@...il.com>:
> From: Jesper Juhl <jesper.juhl@...il.com>
>
> [This patch previously submitted on 24 April 2008 00:18]
>
Hmmm, no feedback at all on this one. Could someone please ACK or NACK it?
I've more stuff like this in the pipeline, but I'm holding it back
until I see if this one takes root or not ;)
/Jesper
>
> This patch reduces the number of sequential pointer derefs in scsi_error
> ( drivers/scsi/scsi_error.c ).
>
> The bennefits are:
> - makes the code easier to read. Lots of sequential derefs of the
> same pointers are not easy on the eye.
> - makes the size of the source file 55 bytes smaller.
> - makes the size of the object file 48 bytes smaller.
> - theoretically at least, just dereferencing the pointers once can
> allow the compiler to generally slightly faster code, so in
> theory this could also be a micro speed optimization.
>
> Please consider applying.
>
>
> Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>
> ---
>
> scsi_error.c | 58 ++++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 32 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 221f31e..94395a7 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -185,13 +185,14 @@ int scsi_delete_timer(struct scsi_cmnd *scmd)
> void scsi_times_out(struct scsi_cmnd *scmd)
> {
> enum scsi_eh_timer_return (* eh_timed_out)(struct scsi_cmnd *);
> + struct Scsi_Host *host = scmd->device->host;
>
> scsi_log_completion(scmd, TIMEOUT_ERROR);
>
> - if (scmd->device->host->transportt->eh_timed_out)
> - eh_timed_out = scmd->device->host->transportt->eh_timed_out;
> - else if (scmd->device->host->hostt->eh_timed_out)
> - eh_timed_out = scmd->device->host->hostt->eh_timed_out;
> + if (host->transportt->eh_timed_out)
> + eh_timed_out = host->transportt->eh_timed_out;
> + else if (host->hostt->eh_timed_out)
> + eh_timed_out = host->hostt->eh_timed_out;
> else
> eh_timed_out = NULL;
>
> @@ -474,22 +475,22 @@ static int scsi_try_host_reset(struct scsi_cmnd *scmd)
> {
> unsigned long flags;
> int rtn;
> + struct Scsi_Host *host = scmd->device->host;
>
> SCSI_LOG_ERROR_RECOVERY(3, printk("%s: Snd Host RST\n",
> __FUNCTION__));
>
> - if (!scmd->device->host->hostt->eh_host_reset_handler)
> + if (!host->hostt->eh_host_reset_handler)
> return FAILED;
>
> - rtn = scmd->device->host->hostt->eh_host_reset_handler(scmd);
> + rtn = host->hostt->eh_host_reset_handler(scmd);
>
> if (rtn == SUCCESS) {
> - if (!scmd->device->host->hostt->skip_settle_delay)
> + if (!host->hostt->skip_settle_delay)
> ssleep(HOST_RESET_SETTLE_TIME);
> - spin_lock_irqsave(scmd->device->host->host_lock, flags);
> - scsi_report_bus_reset(scmd->device->host,
> - scmd_channel(scmd));
> - spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
> + spin_lock_irqsave(host->host_lock, flags);
> + scsi_report_bus_reset(host, scmd_channel(scmd));
> + spin_unlock_irqrestore(host->host_lock, flags);
> }
>
> return rtn;
> @@ -503,22 +504,22 @@ static int scsi_try_bus_reset(struct scsi_cmnd *scmd)
> {
> unsigned long flags;
> int rtn;
> + struct Scsi_Host *host = scmd->device->host;
>
> SCSI_LOG_ERROR_RECOVERY(3, printk("%s: Snd Bus RST\n",
> __FUNCTION__));
>
> - if (!scmd->device->host->hostt->eh_bus_reset_handler)
> + if (!host->hostt->eh_bus_reset_handler)
> return FAILED;
>
> - rtn = scmd->device->host->hostt->eh_bus_reset_handler(scmd);
> + rtn = host->hostt->eh_bus_reset_handler(scmd);
>
> if (rtn == SUCCESS) {
> - if (!scmd->device->host->hostt->skip_settle_delay)
> + if (!host->hostt->skip_settle_delay)
> ssleep(BUS_RESET_SETTLE_TIME);
> - spin_lock_irqsave(scmd->device->host->host_lock, flags);
> - scsi_report_bus_reset(scmd->device->host,
> - scmd_channel(scmd));
> - spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
> + spin_lock_irqsave(host->host_lock, flags);
> + scsi_report_bus_reset(host, scmd_channel(scmd));
> + spin_unlock_irqrestore(host->host_lock, flags);
> }
>
> return rtn;
> @@ -544,16 +545,17 @@ static int scsi_try_target_reset(struct scsi_cmnd *scmd)
> {
> unsigned long flags;
> int rtn;
> + struct Scsi_Host *host = scmd->device->host;
>
> - if (!scmd->device->host->hostt->eh_target_reset_handler)
> + if (!host->hostt->eh_target_reset_handler)
> return FAILED;
>
> - rtn = scmd->device->host->hostt->eh_target_reset_handler(scmd);
> + rtn = host->hostt->eh_target_reset_handler(scmd);
> if (rtn == SUCCESS) {
> - spin_lock_irqsave(scmd->device->host->host_lock, flags);
> + spin_lock_irqsave(host->host_lock, flags);
> __starget_for_each_device(scsi_target(scmd->device), NULL,
> __scsi_report_device_reset);
> - spin_unlock_irqrestore(scmd->device->host->host_lock, flags);
> + spin_unlock_irqrestore(host->host_lock, flags);
> }
>
> return rtn;
> @@ -572,11 +574,12 @@ static int scsi_try_target_reset(struct scsi_cmnd *scmd)
> static int scsi_try_bus_device_reset(struct scsi_cmnd *scmd)
> {
> int rtn;
> + struct Scsi_Host *host = scmd->device->host;
>
> - if (!scmd->device->host->hostt->eh_device_reset_handler)
> + if (!host->hostt->eh_device_reset_handler)
> return FAILED;
>
> - rtn = scmd->device->host->hostt->eh_device_reset_handler(scmd);
> + rtn = host->hostt->eh_device_reset_handler(scmd);
> if (rtn == SUCCESS)
> __scsi_report_device_reset(scmd->device, NULL);
> return rtn;
> @@ -584,10 +587,13 @@ static int scsi_try_bus_device_reset(struct scsi_cmnd *scmd)
>
> static int __scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
> {
> - if (!scmd->device->host->hostt->eh_abort_handler)
> + int (* eh_abort_handler)(struct scsi_cmnd *)
> + = scmd->device->host->hostt->eh_abort_handler;
> +
> + if (!eh_abort_handler)
> return FAILED;
>
> - return scmd->device->host->hostt->eh_abort_handler(scmd);
> + return eh_abort_handler(scmd);
> }
>
> /**
>
>
--
Jesper Juhl <jesper.juhl@...il.com>
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please http://www.expita.com/nomime.html
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