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Date: Mon, 15 Sep 2014 12:25:29 +0200
From: Tomas Henzl <thenzl@...hat.com>
To: Ching Huang <ching2048@...ca.com.tw>
CC: 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 09/15/2014 04:56 AM, Ching Huang wrote:
> On Fri, 2014-09-12 at 15:34 +0200, Tomas Henzl wrote:
>> 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?
> It is just a code simplification.
Yes it is of some kind. But I think it's also a bug, because you have replaced
'firstindex - lastindex' with nothing.
>> 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?
> Agree.
>> Cheers,
>> Tomas
>>
>
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