RE: Software raid0 will crash the file-system, when each disk is 5TB

2007-05-17 Thread Jeff Zheng 
 Fix confirmed, filled the whole 11T hard disk, without crashing.
I presume this would go into 2.6.22

Thanks again.

Jeff

 -Original Message-
 From: [EMAIL PROTECTED] 
 [mailto:[EMAIL PROTECTED] On Behalf Of Jeff Zheng
 Sent: Thursday, 17 May 2007 5:39 p.m.
 To: Neil Brown; [EMAIL PROTECTED]; Michal Piotrowski; Ingo 
 Molnar; linux-raid@vger.kernel.org; 
 [EMAIL PROTECTED]; [EMAIL PROTECTED]
 Subject: RE: Software raid0 will crash the file-system, when 
 each disk is 5TB
 
 
 Yeah, seems you've locked it down, :D. I've written 600GB of 
 data now, and anything is still fine.
 Will let it run overnight, and fill the whole 11T. I'll post 
 the result tomorrow
 
 Thanks a lot though.
 
 Jeff 
 
  -Original Message-
  From: Neil Brown [mailto:[EMAIL PROTECTED]
  Sent: Thursday, 17 May 2007 5:31 p.m.
  To: [EMAIL PROTECTED]; Jeff Zheng; Michal Piotrowski; Ingo Molnar; 
  linux-raid@vger.kernel.org; [EMAIL PROTECTED]; 
  [EMAIL PROTECTED]
  Subject: RE: Software raid0 will crash the file-system, 
 when each disk 
  is 5TB
  
  On Thursday May 17, [EMAIL PROTECTED] wrote:
   
   Uhm, I just noticed something.
   'chunk' is unsigned long, and when it gets shifted up, we
  might lose
   bits.  That could still happen with the 4*2.75T 
 arrangement, but is 
   much more likely in the 2*5.5T arrangement.
  
  Actually, it cannot be a problem with the 4*2.75T arrangement.
chuck  chunksize_bits
  
  will not exceed the size of the underlying device *in*kilobytes*.
  In that case that is 0xAE9EC800 which will git in a 32bit long.
  We don't double it to make sectors until after we add
  zone-dev_offset, which is sector_t and so 64bit 
 arithmetic is used.
  
  So I'm quite certain this bug will cause exactly the problems 
  experienced!!
  
   
   Jeff, can you try this patch?
  
  Don't bother about the other tests I mentioned, just try this one.
  Thanks.
  
  NeilBrown
  
   Signed-off-by: Neil Brown [EMAIL PROTECTED]
   
   ### Diffstat output
./drivers/md/raid0.c |2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
   
   diff .prev/drivers/md/raid0.c ./drivers/md/raid0.c
   --- .prev/drivers/md/raid0.c  2007-05-17 
  10:33:30.0 +1000
   +++ ./drivers/md/raid0.c  2007-05-17 15:02:15.0 +1000
   @@ -475,7 +475,7 @@ static int raid0_make_request (request_q
 x = block  chunksize_bits;
 tmp_dev = zone-dev[sector_div(x, zone-nb_dev)];
 }
   - rsect = (((chunk  chunksize_bits) + zone-dev_offset)1)
   + rsect = sector_t)chunk  chunksize_bits) +
   +zone-dev_offset)1)
 + sect_in_chunk;
 
 bio-bi_bdev = tmp_dev-bdev;
  
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RE: Software raid0 will crash the file-system, when each disk is 5TB

2007-05-17 Thread Neil Brown 
On Friday May 18, [EMAIL PROTECTED] wrote:
  Fix confirmed, filled the whole 11T hard disk, without crashing.
 I presume this would go into 2.6.22

Yes, and probably 2.6.21.y, though the patch will be slightly
different, see below.
 
 Thanks again.

And thank-you for pursuing this with me.

NeilBrown


---
Avoid overflow in raid0 calculation with large components.

If a raid0 has a component device larger than 4TB, and is accessed on
a 32bit machines, then as 'chunk' is unsigned lock,
   chunk  chunksize_bits
can overflow (this can be as high as the size of the device in KB).
chunk itself will not overflow (without triggering a BUG).

So change 'chunk' to be 'sector_t, and get rid of the 'BUG' as it becomes
impossible to hit.

Cc: Jeff Zheng [EMAIL PROTECTED]
Signed-off-by: Neil Brown [EMAIL PROTECTED]

### Diffstat output
 ./drivers/md/raid0.c |3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff .prev/drivers/md/raid0.c ./drivers/md/raid0.c
--- .prev/drivers/md/raid0.c2007-05-17 10:33:30.0 +1000
+++ ./drivers/md/raid0.c2007-05-17 16:14:12.0 +1000
@@ -415,7 +415,7 @@ static int raid0_make_request (request_q
raid0_conf_t *conf = mddev_to_conf(mddev);
struct strip_zone *zone;
mdk_rdev_t *tmp_dev;
-   unsigned long chunk;
+   sector_t chunk;
sector_t block, rsect;
const int rw = bio_data_dir(bio);
 
@@ -470,7 +470,6 @@ static int raid0_make_request (request_q
 
sector_div(x, zone-nb_dev);
chunk = x;
-   BUG_ON(x != (sector_t)chunk);
 
x = block  chunksize_bits;
tmp_dev = zone-dev[sector_div(x, zone-nb_dev)];
-
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