User kernel API

This page was created to help simplifying the user-kernel API for Next3 snapshots, according to suggestions of Ted T'so.

For internal kernel API, see Code documentation#Snapshot_kernel_API.

Table of Contents Taking a snapshot Mounting a snapshot Deleting a snapshot Listing snapshots

Taking a snapshot

Script command: "next3 take NAME"

Current API:

# chattr +x <mntdir>/.snapshots
# touch <mntdir>/.snapshots/<snapfile>
# chattr -X +S <mntdir>/.snapshots/<snapfile>

Simplified API:

# touch <mntdir>/.snapshots/<snapfile>

TODO: Create .snapshots directory on mkfs.next3.

TODO: Invoke snapshot take from create command.

Mounting a snapshot

Script command: "next3 mount NAME"

Current API:

# chattr -X +n <mntdir>/.snapshots/<snapfile>
# mount -r -t ext2 -o loop <mntdir>/.snapshots/<snapfile> <snapmnt>

Simplified API:

# mount -r -o loop,noload <mntdir>/.snapshots/<snapfile> <snapmnt>

TODO: Auto-enable snapshot on snapshot file open.

Deleting a snapshot

Script command: "next3 remove NAME"

Current API:

# umount -d <snapmnt>
# chattr -X -n <mntdir>/.snapshots>/<snapfile>
# chattr -X -S <mntdir>/.snapshots/<snapfile>
# rm <mntdir>/.snapshots/<snapfile> (may fail if snapshot file is in use)

Simplified API:

# umount <snapmnt>
# rm <mntdir>/.snapshots/<snapfile> (queue snapshot for deletion and return EBUSY if snapshot file is in use)

TODO: Auto-disable snapshot on last snapshot file close.

TODO: Invoke snapshot delete from unlink command.

Listing snapshots

Script command: "next3 stat"

Current API:

# lsattr -X <mntdir>/.snapshots

New API:

# lssnap <mntdir>/.snapshots