Re: [PATCH] ext4: Fix fallocate to update the file size in each transaction.

[Eric Sandeen <sandeen@redhat.com>]

Andreas Dilger wrote:
> On Mar 11, 2008  11:25 +0530, Aneesh Kumar K.V wrote:
>> +	-x: run test after preallocating the area (1|2) 2 to not update size.\n\
> 
> The issue with preallocating just a single area in fsx is that this isn't
> much different than starting the test with a single large write or truncate.

except that the filesystem does still have to manage the unwritten
extent splits properly... but I agree that ongoing extending and
non-extending fallocates of various sizes would be very interesting.

-Eric

> What would be a lot more useful is to have fsx continually do fallocate
> requests of variable sizes during the test.  This would be quite similar
> to a "write" operation, except that it wouldn't change any existing data
> and holes would still read back as zero.  The only difference is in the
> "do not update size" test any fallocate at the end of the file would not
> increase the file size.
> 
> This would exercise the fallocate code a LOT because it would put unwritten
> extents in the middle of the file, map a single fallocate to multiple
> discontiguous holes of the file (not overwriting existing allocated data
> in the middle of the file), verify fallocate of an overlapping unwritten
> extent works, etc.
>