net/ceph/snapshot.c

   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         atomic_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                 atomic_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 (atomic_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);