Re: new Areca driver in 2.6.16-rc6-mm2 appears to be broken

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 

Dear Jens Axboe,

I had found a big difference of generic_make_request(struct bio *bio)
got message : sdb1: rw=0, want=...., limit=.....


*****************
** TEST 1
*****************
I used "MAX_XFER_SECTORS 4096" driver to do mkfs.ext2 with ARECA RAID volume sdb1. 
and copy a big file (900MB) into sdb1.
If I copy this file from sdb1, the message rw=.... ,want=......, limit=...... will appear immediately. 

When I reboot the system and used  "MAX_XFER_SECTORS  512" driver.
I copy this big file from sdb1, the message rw=.... ,want=......, limit=...... still appear immediately.
When I redo mkfs.ext2 with ARECA RAID volume sdb1 (used "MAX_XFER_SECTORS 512") 
and copy the same file (900MB) into sdb1.
I copy this file from sdb1 again,the message rw=.... ,want=......, limit=...... disappear. 

****************
** TEST 2
****************

When I do another test with "MAX_XFER_SECTORS  4096" driver

#echo 0 > /sys/block/sdb/queue/read_ahead_kb
#mkfs.ext2 /dev/sdb1

then copy the same file (900MB) into sdb1.
I copy this file from sdb1 again,the message rw=.... ,want=......, limit=...... disappear. Even I redo "echo 4096 > /sys/block/sdb/queue/read_ahead_kb" with ARECA RAID volume. The message rw=.... ,want=......, limit=...... never appear at my "copy compare" test script. 

Now I can say the bug come from "block read ahead".
And this bug will certainly appear when do "mkfs.ext2" if read_ahead_kb value large enough. 


Best Regards
Erich Chen
----- Original Message ----- From: "Jens Axboe" <[email protected]> 
To: "Andrew Morton" <[email protected]>
Cc: "James Bottomley" <[email protected]>; <[email protected]>
Sent: Friday, March 31, 2006 3:42 PM
Subject: Re: new Areca driver in 2.6.16-rc6-mm2 appears to be broken




(irk, Erich wasn't in the cc, sorry to Andrew and James for getting this
mail twice)

On Thu, Mar 30 2006, Andrew Morton wrote:

"erich" <[email protected]> wrote:
>
> Dear Chris Caputo,
>
> Thanks you to conform this issue again, my colleague assisted me and > to 
>  double check my older version driver yesterday.
>  and the old driver is working fine as your mention before.
>
>  The ARCMSR_MAX_XFER_SECTORS is the reason why cause "attempt to access
>  beyond end of device".
>
>  #define ARCMSR_MAX_XFER_SECTORS
>  256     -----old
>  #define ARCMSR_MAX_XFER_SECTORS
>  4096     -----new

That seems odd.  ARCMSR_MAX_XFER_SECTORS just gets put into
scsi_host_template.max_sectors.  Could it be a scsi core buglet?


Perhaps the larger max sectors setting is causing read-ahead to be
overly optimistic and going beyond the end? Should not happen.

Erich, can you try and shrink read-ahead on that device and retest?
Basically just do

# echo 0 > /sys/block/sdX/queue/read_ahead_kb

and see if it still complains.

--
Jens Axboe



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux