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 <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);