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 */
42 struct 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 }
59 EXPORT_SYMBOL(ceph_create_snap_context);
60
61 struct 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 }
67 EXPORT_SYMBOL(ceph_get_snap_context);
68
69 void 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 }
78 EXPORT_SYMBOL(ceph_put_snap_context);
79
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