On 06/03/2016 11:20 PM, Josef Bacik wrote:
On 04/01/2016 02:34 AM, Qu Wenruo wrote:
This patchset can be fetched from github:
https://github.com/adam900710/linux.git wang_dedupe_20160401
In this patchset, we're proud to bring a completely new storage backend:
Khala backend.
With Khala backend, all dedupe hash will be restored in the Khala,
shared with every Kalai protoss, with unlimited storage and almost zero
search latency.
A perfect backend for any Kalai protoss. "My life for Aiur!"
Unfortunately, such backend is not available for human.
OK, except the super-fancy and date-related backend, the patchset is
still a serious patchset.
In this patchset, we mostly addressed the on-disk format change
comment from
Chris:
1) Reduced dedupe hash item and bytenr item.
Now dedupe hash item structure size is reduced from 41 bytes
(9 bytes hash_item + 32 bytes hash)
to 29 bytes (5 bytes hash_item + 24 bytes hash)
Without the last patch, it's even less with only 24 bytes
(24 bytes hash only).
And dedupe bytenr item structure size is reduced from 32 bytes (full
hash) to 0.
2) Hide dedupe ioctls into CONFIG_BTRFS_DEBUG
Advised by David, to make btrfs dedupe as an experimental feature for
advanced user.
This is used to allow this patchset to be merged while still allow us
to change ioctl in the further.
3) Add back missing bug fix patches
I just missed 2 bug fix patches in previous iteration.
Adding them back.
Now patch 1~11 provide the full backward-compatible in-memory backend.
And patch 12~14 provide per-file dedupe flag feature.
Patch 15~20 provide on-disk dedupe backend with persist dedupe state for
in-memory backend.
The last patch is just preparation for possible dedupe-compress co-work.
You can add
Reviewed-by: Josef Bacik <jba...@fb.com>
to everything I didn't comment on (and not the ENOSPC one either, but I
commented on that one last time).
Thanks for the review.
All your comment will be addressed in next version, except ones I commented.
But just because I've reviewed it doesn't mean it's ready to go in.
Before we are going to take this I want to see the following
Right, I won't rush to merge it, and I'm pretty sure you would like to
review the incoming ENOSPC fix further, as the root fix would be a
little complicated and affects a lot of common routines.
1) fsck support for dedupe that verifies the hashes with what is on disk
Nice advice, if hash pool is screwed up, the whole fs will be screwed up.
But that's for on-disk backend, and unfortunately, on-disk backend will
be excluded in next version.
On-disk backend will only be re-introduced after in-memory backend only
patchset.
so any xfstests we write are sure to catch problems.
2) xfstests. They need to do the following things for both in memory
and ondisk
a) targeted verification. So write one pattern, write the same
pattern to a different file and use fiemap to verify they are the
same.
Already in previous xfstests patchset.
But need a little modification, as we may merge in-mem and on-disk
backend in different kernel merge windows, so test cases may be split
for different backends.
I'll update xfstest with V11 patchset, to do in-mem only checks.
b) modify fsstress to have an option to always write the same
pattern and then run a stress test while balancing.
We already had such test cases, and even with current fsstress, its
pattern is already good enough to trigger some bug in our test cases.
But it's still a good idea to make fsstress to reproduce dedupe bugs
more preciously.
Thanks,
Qu
Once the issues I've hilighted in the other patches are resolved and the
above xfstests things are merged and the fsck patches are
reviewed/accepted then we can move forward with including dedup. Thanks,
Josef
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