On 09/20/2011 03:00 PM, Alex Elder wrote:
> On Mon, 2011-09-19 at 16:45 -0500, Eric Sandeen wrote:
>> RH QA discovered this bug:
>>
>> Steps to Reproduce:
>> 1. Create 4 TB - 1 B partition
>> dd if=/dev/zero of=x.img bs=1 count=0 seek=4398046511103
>> 2. Create xfs fs with 512 B block size on the partition
>> mkfs.xfs -b size=512 xfs.img
>>
>> Actual results:
>> Agsize is computed incorrectly resulting in fs creation fail:
>> agsize (2147483648b) too big, maximum is 2147483647 blocks
>>
>> This is due to the "rounding up" at the very end of the calculations;
>> there may be other places to alleviate the problem, but it seems
>> most obvious to simply skip the rounding up if it would create too
>> many blocks in the AG. Worst case, we lose 1 block per AG.
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>
> The fix is the right way about it.
>
> This may seem petty, but I think this would be better:
>
> blocks = dblocks >> shift
> if (blocks & xfs_mask32lo(shift)) {
> if (blocks < XFS_AG_MAX_BLOCKS(blocklog))
> blocks++;
> }
>
> It emphasizes more why we'd be doing the increment,
> plus I'd rather see a "real" increment rather than
> adding a Boolean value.
Yes, that's probably better. More code change ... making it more readable.
I'll check it in that way (or, maybe you can, since I can't reach the
git repo)?
Thanks,
-Eric
> Either way:
> Reviewed-by: Alex Elder <aelder@xxxxxxx>
>
>> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
>> index 5b3b9a7..856a261 100644
>> --- a/mkfs/xfs_mkfs.c
>> +++ b/mkfs/xfs_mkfs.c
>> @@ -658,7 +659,9 @@ calc_default_ag_geometry(
>> * last bit of the filesystem. The same principle applies
>> * to the AG count, so we don't lose the last AG!
>> */
>> - blocks = (dblocks >> shift) + ((dblocks & xfs_mask32lo(shift)) != 0);
>> + blocks = (dblocks >> shift);
>> + if (blocks < XFS_AG_MAX_BLOCKS(blocklog))
>> + blocks += ((dblocks & xfs_mask32lo(shift)) != 0);
>>
>> done:
>> *agsize = blocks;
>>
>> _______________________________________________
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>> xfs@xxxxxxxxxxx
>> http://oss.sgi.com/mailman/listinfo/xfs
>
>
>
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