Re: [PATCH v5 00/10] speculative preallocation inode tracking

Mark Tinguely
2012-10-21T17:51:46Z

On 10/21/12 09:00, Brian Foster wrote:
> On 10/19/2012 05:02 PM, Mark Tinguely wrote:
>> On 10/05/12 09:17, Brian Foster wrote:
>>> Hi all,
>>>
>>> This is v3 of the speculative preallocation inode tracking patchset. This
>>> functionality tracks inodes with post-EOF speculative preallocation
>>> for the
>>> purpose of background and on-demand trimming.
>>>
>>> Background scanning occurs on a longish interval (5 minutes by
>>> default) and in
>>> a best-effort mode (i.e., inodes are skipped due to lock contention or
>>> dirty
>>> cache). The intent is to clear up post-EOF blocks on inodes that might
>>> have
>>> allocations hanging around due to open-write-close sequences (NFS).
>>>
>>> On demand scanning is provided via a new ioctl and supports various
>>> parameters
>>> such as scan mode, filtering by quota id and minimum file size. A
>>> pending use
>>> case for on demand scanning is for accurate quota accounting via the
>>> gluster
>>> scale out filesystem (i.e., to free up preallocated space when near a
>>> usage
>>> limit).
>>>
>>> Brian
>>
>> The series looks great.
>>
>
> Hi Mark,
>
> Thanks for the review.
>
>> I am just curious, what is the reason for the padding in the
>> xfs_eofblocks structure?
>>
>
> I added the padding in response to review on an early revision of the set:
>
> http://oss.sgi.com/archives/xfs/2012-09/msg00024.html
>
> The purpose is to allow adding fields to the control structure down the
> road without breaking existing binaries.
>
> Brian
>
>> Reviewed-by: Mark Tinguely<tinguely@sgi.com>
>

Thank-you for the information.

I would think that changing the number of arguments would also
involving changing the version number. The kernel should know
that version 1 copies in 16 bytes, version 2 copies in 16+t bytes,
version n copies in 16+n bytes...

Not at all a big deal, (16 used and 12 padding = ) 28 bytes was an
odd number and it got my curiosity up. I suspected it was part a plan
of yours and Pinky to take over the world. :)

Nice feature. I jury-rigged a ioctl to test and it works great. I look
forwarded to seeing this in xfs_io.

--Mark.