From: Kent Overstreet <kent.overstreet@gmail.com>
To: linux-kernel@vger.kernel.org, linux-bcachefs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: bcachefs - snapshots
Date: Sun, 26 Sep 2021 21:49:07 -0400 [thread overview]
Message-ID: <YVEjEwCiqje7yDyV@moria.home.lan> (raw)
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.
next reply other threads:[~2021-09-27 1:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 1:49 Kent Overstreet [this message]
2021-09-27 13:06 ` bcachefs - snapshots Bernd Schubert
2021-09-27 16:43 ` Frank Filz
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