* bcachefs - snapshots
@ 2021-09-27 1:49 Kent Overstreet
2021-09-27 13:06 ` Bernd Schubert
0 siblings, 1 reply; 3+ messages in thread
From: Kent Overstreet @ 2021-09-27 1:49 UTC (permalink / raw)
To: linux-kernel, linux-bcachefs, linux-fsdevel
Snapshots have been merged! 9 months of work and 3k lines of new code, finally
released. Some highlights:
- btrfs style subvolumes & snapshots interface
- snapshots are writeable
- highly scalable: number of snapshots is limited only by your disk space
- highly space efficient: no internal fragmentation issues
Design doc here: https://bcachefs.org/Snapshots/
The core functionality is complete - snapshot creation and deletion works, fsck
changes are done (most of the complexity was in making fsck work without
O(number of snapshots) performance - tricky). Everything else is a todo item:
- still need to export different st_dev for files in different subvolumes
(we'll never allocate a new inode with an inode number that collides with an
inode inother subvolume - but snapshots will naturally result in colliding
inode numbers)
- need to hide dirents that point to snapshots when inside snapshots...
- snapshot creation is not atomic w.r.t. page cache, we do sync_fs() but don't
block buffered writes
- other niggling page cache stuff - need to walk page cache and mark blocks as
no longer reserved on snapshot creation
- we no longer have quota support, since old style quotas interact badly with
snapshots
- we need per subvolume disk space accounting before i can implement btrfs
style subvolume quotas
- all the things I neglected to think of yet, and all the bugs I haven't found
yet
Go wild, please try and break it.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: bcachefs - snapshots
2021-09-27 1:49 bcachefs - snapshots Kent Overstreet
@ 2021-09-27 13:06 ` Bernd Schubert
2021-09-27 16:43 ` Frank Filz
0 siblings, 1 reply; 3+ messages in thread
From: Bernd Schubert @ 2021-09-27 13:06 UTC (permalink / raw)
To: Kent Overstreet, linux-kernel, linux-bcachefs, linux-fsdevel
On 9/27/21 3:49 AM, Kent Overstreet wrote:
> Snapshots have been merged! 9 months of work and 3k lines of new code, finally
> released. Some highlights:
>
> - btrfs style subvolumes & snapshots interface
> - snapshots are writeable
> - highly scalable: number of snapshots is limited only by your disk space
> - highly space efficient: no internal fragmentation issues
>
> Design doc here: https://bcachefs.org/Snapshots/
>
> The core functionality is complete - snapshot creation and deletion works, fsck
> changes are done (most of the complexity was in making fsck work without
> O(number of snapshots) performance - tricky). Everything else is a todo item:
>
> - still need to export different st_dev for files in different subvolumes
> (we'll never allocate a new inode with an inode number that collides with an
> inode inother subvolume - but snapshots will naturally result in colliding
> inode numbers)
With my limited high level view on it - shouldn't you discuss with Neil
about a solution and to avoid going the btrfs route for colliding inode
numbers?
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: bcachefs - snapshots
2021-09-27 13:06 ` Bernd Schubert
@ 2021-09-27 16:43 ` Frank Filz
0 siblings, 0 replies; 3+ messages in thread
From: Frank Filz @ 2021-09-27 16:43 UTC (permalink / raw)
To: 'Bernd Schubert', 'Kent Overstreet',
linux-kernel, linux-bcachefs, linux-fsdevel
> On 9/27/21 3:49 AM, Kent Overstreet wrote:
> > Snapshots have been merged! 9 months of work and 3k lines of new code,
> > finally released. Some highlights:
> >
> > - btrfs style subvolumes & snapshots interface
> > - snapshots are writeable
> > - highly scalable: number of snapshots is limited only by your disk
> > space
> > - highly space efficient: no internal fragmentation issues
> >
> > Design doc here: https://bcachefs.org/Snapshots/
> >
> > The core functionality is complete - snapshot creation and deletion
> > works, fsck changes are done (most of the complexity was in making
> > fsck work without O(number of snapshots) performance - tricky). Everything
> else is a todo item:
> >
> > - still need to export different st_dev for files in different subvolumes
> > (we'll never allocate a new inode with an inode number that collides with an
> > inode inother subvolume - but snapshots will naturally result in colliding
> > inode numbers)
>
> With my limited high level view on it - shouldn't you discuss with Neil about a
> solution and to avoid going the btrfs route for colliding inode numbers?
I was going to ask that also having been watching the btrfs subvolume saga. As maintainer of the Ganesha user space NFS server I have an interest in this also though we haven't had anyone talk about bcachefs yet.
Frank
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-09-27 16:48 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-09-27 1:49 bcachefs - snapshots Kent Overstreet
2021-09-27 13:06 ` Bernd Schubert
2021-09-27 16:43 ` Frank Filz
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