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Message-ID: <5412F680.2070702@redhat.com>
Date: Fri, 12 Sep 2014 15:34:56 +0200
From: Tomas Henzl <thenzl@...hat.com>
To: Ching Huang <ching2048@...ca.com.tw>, hch@...radead.org,
jbottomley@...allels.com, dan.carpenter@...cle.com,
agordeev@...hat.com, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] arcmsr: simplify ioctl data read/write
On 09/12/2014 09:29 AM, Ching Huang wrote:
> From: Ching Huang <ching2048@...ca.com.tw>
>
> This patch is to modify previous patch 13/17 and it is relative to
> http://git.infradead.org/users/hch/scsi-queue.git/tree/arcmsr-for-3.18:/drivers/scsi/arcmsr
>
> change in v4:
> 1. for readability, rename firstindex to getIndex, rename lastindex to putIndex
For some reason, the names head+tail areusual for a circular buffer.
But let us ignore the names, I don't care.
> 2. define ARCMSR_API_DATA_BUFLEN as 1032
> 3. simplify ioctl data read by macro CIRC_CNT_TO_END and CIRC_CNT
It's definitely better when you post renames and other non-functional changes in separate
patches, it's easier for the reviewer.
>
> Signed-off-by: Ching Huang <ching2048@...ca.com.tw>
> ---
>
> diff -uprN a/drivers/scsi/arcmsr/arcmsr_attr.c b/drivers/scsi/arcmsr/arcmsr_attr.c
> --- a/drivers/scsi/arcmsr/arcmsr_attr.c 2014-08-21 12:14:27.000000000 +0800
> +++ b/drivers/scsi/arcmsr/arcmsr_attr.c 2014-09-12 15:18:46.659125000 +0800
> @@ -50,6 +50,7 @@
> #include <linux/errno.h>
> #include <linux/delay.h>
> #include <linux/pci.h>
> +#include <linux/circ_buf.h>
>
> #include <scsi/scsi_cmnd.h>
> #include <scsi/scsi_device.h>
> @@ -68,7 +69,7 @@ static ssize_t arcmsr_sysfs_iop_message_
> struct device *dev = container_of(kobj,struct device,kobj);
> struct Scsi_Host *host = class_to_shost(dev);
> struct AdapterControlBlock *acb = (struct AdapterControlBlock *) host->hostdata;
> - uint8_t *pQbuffer,*ptmpQbuffer;
> + uint8_t *ptmpQbuffer;
> int32_t allxfer_len = 0;
> unsigned long flags;
>
> @@ -78,57 +79,22 @@ static ssize_t arcmsr_sysfs_iop_message_
> /* do message unit read. */
> ptmpQbuffer = (uint8_t *)buf;
> spin_lock_irqsave(&acb->rqbuffer_lock, flags);
> - if (acb->rqbuf_firstindex != acb->rqbuf_lastindex) {
> - pQbuffer = &acb->rqbuffer[acb->rqbuf_firstindex];
> - if (acb->rqbuf_firstindex > acb->rqbuf_lastindex) {
> - if ((ARCMSR_MAX_QBUFFER - acb->rqbuf_firstindex) >= 1032) {
> - memcpy(ptmpQbuffer, pQbuffer, 1032);
> - acb->rqbuf_firstindex += 1032;
> - acb->rqbuf_firstindex %= ARCMSR_MAX_QBUFFER;
> - allxfer_len = 1032;
> - } else {
> - if (((ARCMSR_MAX_QBUFFER - acb->rqbuf_firstindex)
> - + acb->rqbuf_lastindex) > 1032) {
> - memcpy(ptmpQbuffer, pQbuffer,
> - ARCMSR_MAX_QBUFFER
> - - acb->rqbuf_firstindex);
> - ptmpQbuffer += ARCMSR_MAX_QBUFFER
> - - acb->rqbuf_firstindex;
> - memcpy(ptmpQbuffer, acb->rqbuffer, 1032
> - - (ARCMSR_MAX_QBUFFER -
> - acb->rqbuf_firstindex));
> - acb->rqbuf_firstindex = 1032 -
> - (ARCMSR_MAX_QBUFFER -
> - acb->rqbuf_firstindex);
> - allxfer_len = 1032;
> - } else {
> - memcpy(ptmpQbuffer, pQbuffer,
> - ARCMSR_MAX_QBUFFER -
> - acb->rqbuf_firstindex);
> - ptmpQbuffer += ARCMSR_MAX_QBUFFER -
> - acb->rqbuf_firstindex;
> - memcpy(ptmpQbuffer, acb->rqbuffer,
> - acb->rqbuf_lastindex);
> - allxfer_len = ARCMSR_MAX_QBUFFER -
> - acb->rqbuf_firstindex +
> - acb->rqbuf_lastindex;
> - acb->rqbuf_firstindex =
> - acb->rqbuf_lastindex;
> - }
> - }
> - } else {
> - if ((acb->rqbuf_lastindex - acb->rqbuf_firstindex) > 1032) {
> - memcpy(ptmpQbuffer, pQbuffer, 1032);
> - acb->rqbuf_firstindex += 1032;
> - allxfer_len = 1032;
> - } else {
> - memcpy(ptmpQbuffer, pQbuffer, acb->rqbuf_lastindex
> - - acb->rqbuf_firstindex);
> - allxfer_len = acb->rqbuf_lastindex -
> - acb->rqbuf_firstindex;
> - acb->rqbuf_firstindex = acb->rqbuf_lastindex;
> - }
> + if (acb->rqbuf_getIndex != acb->rqbuf_putIndex) {
> + unsigned int tail = acb->rqbuf_getIndex;
> + unsigned int head = acb->rqbuf_putIndex;
> + unsigned int cnt_to_end = CIRC_CNT_TO_END(head, tail, ARCMSR_MAX_QBUFFER);
> +
> + allxfer_len = CIRC_CNT(head, tail, ARCMSR_MAX_QBUFFER);
> + if (allxfer_len > ARCMSR_API_DATA_BUFLEN)
> + allxfer_len = ARCMSR_API_DATA_BUFLEN;
> +
> + if (allxfer_len <= cnt_to_end)
> + memcpy(ptmpQbuffer, acb->rqbuffer + tail, allxfer_len);
> + else {
> + memcpy(ptmpQbuffer, acb->rqbuffer + tail, cnt_to_end);
> + memcpy(ptmpQbuffer + cnt_to_end, acb->rqbuffer, allxfer_len - cnt_to_end);
> }
> + acb->rqbuf_getIndex = (acb->rqbuf_getIndex + allxfer_len) % ARCMSR_MAX_QBUFFER;
> }
> if (acb->acb_flags & ACB_F_IOPDATA_OVERFLOW) {
> struct QBUFFER __iomem *prbuffer;
> @@ -150,33 +116,32 @@ static ssize_t arcmsr_sysfs_iop_message_
> struct device *dev = container_of(kobj,struct device,kobj);
> struct Scsi_Host *host = class_to_shost(dev);
> struct AdapterControlBlock *acb = (struct AdapterControlBlock *) host->hostdata;
> - int32_t my_empty_len, user_len, wqbuf_firstindex, wqbuf_lastindex;
> + int32_t my_empty_len, user_len, wqbuf_getIndex, wqbuf_putIndex;
> uint8_t *pQbuffer, *ptmpuserbuffer;
> unsigned long flags;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
> - if (count > 1032)
> + if (count > ARCMSR_API_DATA_BUFLEN)
> return -EINVAL;
> /* do message unit write. */
> ptmpuserbuffer = (uint8_t *)buf;
> user_len = (int32_t)count;
> spin_lock_irqsave(&acb->wqbuffer_lock, flags);
> - wqbuf_lastindex = acb->wqbuf_lastindex;
> - wqbuf_firstindex = acb->wqbuf_firstindex;
> - if (wqbuf_lastindex != wqbuf_firstindex) {
> + wqbuf_putIndex = acb->wqbuf_putIndex;
> + wqbuf_getIndex = acb->wqbuf_getIndex;
> + if (wqbuf_putIndex != wqbuf_getIndex) {
> arcmsr_write_ioctldata2iop(acb);
> spin_unlock_irqrestore(&acb->wqbuffer_lock, flags);
> return 0; /*need retry*/
> } else {
> - my_empty_len = (wqbuf_firstindex-wqbuf_lastindex - 1)
> - &(ARCMSR_MAX_QBUFFER - 1);
> + my_empty_len = ARCMSR_MAX_QBUFFER - 1;
This^ doesn't look like like an rename can you explain?
Let us stop here, or we end in an endless loop of corrections. The original 13/17
you are trying to improve here was at least without bugs (better said I haven't noticed) so
improving it now only complicates the process.
My suggestion is -let us skip this patch and focus only on fixing the spinlock problem found in 16/17.
OKay?
Cheers,
Tomas
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