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