On 2010-03-27, at 09:07, Theodore Ts'o wrote:
I was monitoring the progress of a distributed download program, and
saw
the following output from two runs of filefrag taken a few seconds
apart:
8 790 8825663 8825551 65
9 855 0 8825727 319 unknown,delalloc
10 1174 8798367 318 128
7 790 8825663 8825559 69
8 1174 8798367 8825731 128
The length of the delalloc extent, 319, is bogus. The 319 seems to
come
from 1174 - 855. But it's not actually the number of delayed
allocation blocks, as we can see when the blocks finally get written;
apparently it was only 4 blocks long.
I'm surprised it shows anything at all for delalloc blocks, since
AFAIK FIEMAP is only walking the extent tree. It would be interesting
if it walked the VM pagetable for unallocated extents in the file, and
beyond i_size.
I don't have time to try to track this down just now, and it's not all
that serious a bug since delalloc regions are by definition highly
transient, but it does look like we have a bug here.
Cheers, Andreas
--
Andreas Dilger
Principal Engineer, Lustre Group
Oracle Corporation Canada Inc.
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
