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

Neil Brown
2007-05-18T00:22:22Z

On Friday May 18, Jeff.Zheng@endace.com 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" <Jeff.Zheng@endace.com>
Signed-off-by: Neil Brown <neilb@suse.de>

### 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.c 2007-05-17 10:33:30.000000000 +1000
+++ ./drivers/md/raid0.c 2007-05-17 16:14:12.000000000 +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)];