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