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 <linux/types.h>
22 #include <linux/export.h>
23 #include <linux/ceph/libceph.h>
24
25 /*
26 * Ceph snapshot contexts are reference counted objects, and the
27 * returned structure holds a single reference. Acquire additional
28 * references with ceph_get_snap_context(), and release them with
29 * ceph_put_snap_context(). When the reference count reaches zero
30 * the entire structure is freed.
31 */
32
33 /*
34 * Create a new ceph snapshot context large enough to hold the
35 * indicated number of snapshot ids (which can be 0). Caller has
36 * to fill in snapc->seq and snapc->snaps[0..snap_count-1].
37 *
38 * Returns a null pointer if an error occurs.
39 */
40 struct ceph_snap_context *ceph_create_snap_context(u32 snap_count,
41 gfp_t gfp_flags)
42 {
43 struct ceph_snap_context *snapc;
44 size_t size;
45
46 size = sizeof (struct ceph_snap_context);
47 size += snap_count * sizeof (snapc->snaps[0]);
48 snapc = kzalloc(size, gfp_flags);
49 if (!snapc)
50 return NULL;
51
52 refcount_set(&snapc->nref, 1);
53 snapc->num_snaps = snap_count;
54
55 return snapc;
56 }
57 EXPORT_SYMBOL(ceph_create_snap_context);
58
59 struct ceph_snap_context *ceph_get_snap_context(struct ceph_snap_context *sc)
60 {
61 if (sc)
62 refcount_inc(&sc->nref);
63 return sc;
64 }
65 EXPORT_SYMBOL(ceph_get_snap_context);
66
67 void ceph_put_snap_context(struct ceph_snap_context *sc)
68 {
69 if (!sc)
70 return;
71 if (refcount_dec_and_test(&sc->nref)) {
72 /*printk(" deleting snap_context %p\n", sc);*/
73 kfree(sc);
74 }
75 }
76 EXPORT_SYMBOL(ceph_put_snap_context);
77
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