Re: [PATCH v4 1/2] arcmsr: simplify ioctl data read/write

From: Ching Huang
Date: Sun Sep 14 2014 - 22:57:05 EST

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@xxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxx>
> > ---
> >
> > 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.
>
> 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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