1/*
2 * snapshot.c    Ceph snapshot context utility routines (part of libceph)
3 *
4 * Copyright (C) 2013 Inktank Storage, Inc.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * version 2 as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 * 02110-1301, USA.
19 */
20
21#include <stddef.h>
22
23#include <linux/types.h>
24#include <linux/export.h>
25#include <linux/ceph/libceph.h>
26
27/*
28 * Ceph snapshot contexts are reference counted objects, and the
29 * returned structure holds a single reference.  Acquire additional
30 * references with ceph_get_snap_context(), and release them with
31 * ceph_put_snap_context().  When the reference count reaches zero
32 * the entire structure is freed.
33 */
34
35/*
36 * Create a new ceph snapshot context large enough to hold the
37 * indicated number of snapshot ids (which can be 0).  Caller has
38 * to fill in snapc->seq and snapc->snaps[0..snap_count-1].
39 *
40 * Returns a null pointer if an error occurs.
41 */
42struct ceph_snap_context *ceph_create_snap_context(u32 snap_count,
43						gfp_t gfp_flags)
44{
45	struct ceph_snap_context *snapc;
46	size_t size;
47
48	size = sizeof (struct ceph_snap_context);
49	size += snap_count * sizeof (snapc->snaps[0]);
50	snapc = kzalloc(size, gfp_flags);
51	if (!snapc)
52		return NULL;
53
54	atomic_set(&snapc->nref, 1);
55	snapc->num_snaps = snap_count;
56
57	return snapc;
58}
59EXPORT_SYMBOL(ceph_create_snap_context);
60
61struct ceph_snap_context *ceph_get_snap_context(struct ceph_snap_context *sc)
62{
63	if (sc)
64		atomic_inc(&sc->nref);
65	return sc;
66}
67EXPORT_SYMBOL(ceph_get_snap_context);
68
69void ceph_put_snap_context(struct ceph_snap_context *sc)
70{
71	if (!sc)
72		return;
73	if (atomic_dec_and_test(&sc->nref)) {
74		/*printk(" deleting snap_context %p\n", sc);*/
75		kfree(sc);
76	}
77}
78EXPORT_SYMBOL(ceph_put_snap_context);
79