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----- Forwarded message from Anders Henke <[EMAIL PROTECTED]> -----

Date:   Thu, 29 Nov 2007 13:31:50 +0100
From: Anders Henke <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: broken dpt_i2o in 2.6.23 (was: ext2_check_page: bad entry in 
directory)
User-Agent: Mutt/1.5.13 (2006-08-11)

On November 28 2007, Anders Henke wrote:
> As "everything is reported as being zero" is quite odd an Jan took a
> guess that it might be block-layer or driver-related, I've assumed
> that the driver is responsible for this; just out of the curiousity, 
> I've manually replaced the dpt_i2o driver by the 2.6.19 one by copying 
> driver/scsi/dpt_i2o.c driver/scsi/dpti.h and driver/scsi/dpt/ into a 
> vanilla 2.6.23.1. kernel; using this kernel fixed the issue for me.
> 
> I haven't yet fine-tested from which kernel release on the dpt_i2o driver 
> behaves like this and spews out zeroed blocks when trying to mount
> the rootfs. Maybe this is just some timing issue.

I've started the fine-tests and can say so far that dpt_i2o from 
2.6.22 is still fine. Test is simple:

[EMAIL PROTECTED]:/usr/src/linux-2.6.22/drivers/scsi/dpt$ cp -r dpt/ dpt_i2o.c 
dpti.h /usr/src/linux-2.6.23.1/drivers/scsi/

... recompile the kernel, reboot: works.

2.6.22 and 2.6.23 differ in terms of the dpt_i2o driver by two different
patch sets:
-one 2 Kb small set of patches from 2.6.22 to 2.6.22-rc1
-one 7 Kb set of patches from 2.6.23-rc2 to 2.6.23-rc3
-one 162 Kb set of patches from 2.6.23-rc9 to 2.6.23-rc10.

When applying the 2.6.23-rc1-based driver to "my" 2.6.31.1 kernel,
the "zero blocks"-symptom show up, so it's the "lucky" situation
that the smallest patch actually seams to be the broken one.

According to the 2.6.23-rc1 short-form changelog, there is
one major edit on the dpt_i2o driver:

FUJITA Tomonori 

      [SCSI] dpt_i2o: convert to use the data buffer accessors

Stephen Rothwell 
      dpt_i2o depends on virt_to_bus

Fujita, would you please take a look at this?

I think that something's broken in there, leading to the dpt_i2o 
sending out blocks of zeroes right after initialization, at least on
some specific controllers (in this case, Adaptec 2010S on Intel
SE7501WV2S-based boxes).

I don't have insight kernel driver development knowledge, so I'm
quite out of help right now. Nevertheless, I'll add the diff
from 2.6.22 to 2.6.23-rc1 in terms of dpt_i2o:

---cut
diff -Nur linux-2.6.22/drivers/scsi/dpt_i2o.c 
linux-2.6.23-rc1/drivers/scsi/dpt_i2o.c
--- linux-2.6.22/drivers/scsi/dpt_i2o.c 2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.23-rc1/drivers/scsi/dpt_i2o.c     2007-07-22 22:41:00.000000000 
+0200
@@ -2078,12 +2078,13 @@
        u32 *lenptr;
        int direction;
        int scsidir;
+       int nseg;
        u32 len;
        u32 reqlen;
        s32 rcode;
 
        memset(msg, 0 , sizeof(msg));
-       len = cmd->request_bufflen;
+       len = scsi_bufflen(cmd);
        direction = 0x00000000; 
        
        scsidir = 0x00000000;                   // DATA NO XFER
@@ -2140,21 +2141,21 @@
        lenptr=mptr++;          /* Remember me - fill in when we know */
        reqlen = 14;            // SINGLE SGE
        /* Now fill in the SGList and command */
-       if(cmd->use_sg) {
-               struct scatterlist *sg = (struct scatterlist 
*)cmd->request_buffer;
-               int sg_count = pci_map_sg(pHba->pDev, sg, cmd->use_sg,
-                               cmd->sc_data_direction);
 
+       nseg = scsi_dma_map(cmd);
+       BUG_ON(nseg < 0);
+       if (nseg) {
+               struct scatterlist *sg;
 
                len = 0;
-               for(i = 0 ; i < sg_count; i++) {
+               scsi_for_each_sg(cmd, sg, nseg, i) {
                        *mptr++ = direction|0x10000000|sg_dma_len(sg);
                        len+=sg_dma_len(sg);
                        *mptr++ = sg_dma_address(sg);
-                       sg++;
+                       /* Make this an end of list */
+                       if (i == nseg - 1)
+                               mptr[-2] = direction|0xD0000000|sg_dma_len(sg);
                }
-               /* Make this an end of list */
-               mptr[-2] = direction|0xD0000000|sg_dma_len(sg-1);
                reqlen = mptr - msg;
                *lenptr = len;
                
@@ -2163,16 +2164,8 @@
                                len, cmd->underflow);
                }
        } else {
-               *lenptr = len = cmd->request_bufflen;
-               if(len == 0) {
-                       reqlen = 12;
-               } else {
-                       *mptr++ = 0xD0000000|direction|cmd->request_bufflen;
-                       *mptr++ = pci_map_single(pHba->pDev,
-                               cmd->request_buffer,
-                               cmd->request_bufflen,
-                               cmd->sc_data_direction);
-               }
+               *lenptr = len = 0;
+               reqlen = 12;
        }
        
        /* Stick the headers on */
@@ -2232,7 +2225,7 @@
        hba_status = detailed_status >> 8;
 
        // calculate resid for sg 
-       cmd->resid = cmd->request_bufflen - readl(reply+5);
+       scsi_set_resid(cmd, scsi_bufflen(cmd) - readl(reply+5));
 
        pHba = (adpt_hba*) cmd->device->host->hostdata[0];
 
---cut

Personally I guess that it's the large drop from lines 2164 on
that's broken, who replaces a mapping routine by some static assignment.


Regards,

Anders
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