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Date: Mon, 15 Sep 2014 13:50:31 +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 12:36 PM, Ching Huang wrote:
> On Mon, 2014-09-15 at 12:25 +0200, Tomas Henzl wrote:
>> 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.
> It will be not a bug. At here, firstindex == lastindex, so firstindex-lastindex is 0
Thanks, I haven't seen it before. In that case because user_len is max 1032 and ARCMSR_MAX_QBUFFER is 4k
the next if statement '(my_empty_len >= user_len)' will be true for any user_len (<1032),
and it looks like you could remove my_empty_len completely.
>>>> 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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