linux/Documentation/ABI/testing/sysfs-bus-rbd
Alex Elder 02cdb02cea rbd: kill create_snap sysfs entry
Josh proposed the following change, and I don't think I could
explain it any better than he did:

    From: Josh Durgin <josh.durgin@inktank.com>
    Date: Tue, 24 Jul 2012 14:22:11 -0700
    To: ceph-devel <ceph-devel@vger.kernel.org>
    Message-ID: <500F1203.9050605@inktank.com>

    Right now the kernel still has one piece of rbd management
    duplicated from the rbd command line tool: snapshot creation.
    There's nothing special about snapshot creation that makes it
    advantageous to do from the kernel, so I'd like to remove the
    create_snap sysfs interface.  That is,
	/sys/bus/rbd/devices/<id>/create_snap
    would be removed.

    Does anyone rely on the sysfs interface for creating rbd
    snapshots?  If so, how hard would it be to replace with:

	rbd snap create pool/image@snap

    Is there any benefit to the sysfs interface that I'm missing?

    Josh

This patch implements this proposal, removing the code that
implements the "snap_create" sysfs interface for rbd images.
As a result, quite a lot of other supporting code goes away.

Suggested-by: Josh Durgin <josh.durgin@inktank.com>
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
2012-10-01 14:30:53 -05:00

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What: /sys/bus/rbd/
Date: November 2010
Contact: Yehuda Sadeh <yehuda@newdream.net>,
Sage Weil <sage@newdream.net>
Description:
Being used for adding and removing rbd block devices.
Usage: <mon ip addr> <options> <pool name> <rbd image name> [snap name]
$ echo "192.168.0.1 name=admin rbd foo" > /sys/bus/rbd/add
The snapshot name can be "-" or omitted to map the image read/write. A <dev-id>
will be assigned for any registered block device. If snapshot is used, it will
be mapped read-only.
Removal of a device:
$ echo <dev-id> > /sys/bus/rbd/remove
Entries under /sys/bus/rbd/devices/<dev-id>/
--------------------------------------------
client_id
The ceph unique client id that was assigned for this specific session.
major
The block device major number.
name
The name of the rbd image.
image_id
The unique id for the rbd image. (For rbd image format 1
this is empty.)
pool
The name of the storage pool where this rbd image resides.
An rbd image name is unique within its pool.
pool_id
The unique identifier for the rbd image's pool. This is
a permanent attribute of the pool. A pool's id will never
change.
size
The size (in bytes) of the mapped block device.
refresh
Writing to this file will reread the image header data and set
all relevant datastructures accordingly.
current_snap
The current snapshot for which the device is mapped.
snap_*
A directory per each snapshot
Entries under /sys/bus/rbd/devices/<dev-id>/snap_<snap-name>
-------------------------------------------------------------
snap_id
The rados internal snapshot id assigned for this snapshot
snap_size
The size of the image when this snapshot was taken.