Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph...

[karo-tx-linux.git] / net / ceph / snapshot.c

diff --git a/net/ceph/snapshot.c b/net/ceph/snapshot.c
new file mode 100644 (file)
index 0000000..154683f
--- /dev/null
+++ b/net/ceph/snapshot.c
@@ -0,0 +1,78 @@
+/*
+ * snapshot.c    Ceph snapshot context utility routines (part of libceph)
+ *
+ * Copyright (C) 2013 Inktank Storage, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include <stddef.h>
+
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/ceph/libceph.h>
+
+/*
+ * Ceph snapshot contexts are reference counted objects, and the
+ * returned structure holds a single reference.  Acquire additional
+ * references with ceph_get_snap_context(), and release them with
+ * ceph_put_snap_context().  When the reference count reaches zero
+ * the entire structure is freed.
+ */
+
+/*
+ * Create a new ceph snapshot context large enough to hold the
+ * indicated number of snapshot ids (which can be 0).  Caller has
+ * to fill in snapc->seq and snapc->snaps[0..snap_count-1].
+ *
+ * Returns a null pointer if an error occurs.
+ */
+struct ceph_snap_context *ceph_create_snap_context(u32 snap_count,
+                                               gfp_t gfp_flags)
+{
+       struct ceph_snap_context *snapc;
+       size_t size;
+
+       size = sizeof (struct ceph_snap_context);
+       size += snap_count * sizeof (snapc->snaps[0]);
+       snapc = kzalloc(size, gfp_flags);
+       if (!snapc)
+               return NULL;
+
+       atomic_set(&snapc->nref, 1);
+       snapc->num_snaps = snap_count;
+
+       return snapc;
+}
+EXPORT_SYMBOL(ceph_create_snap_context);
+
+struct ceph_snap_context *ceph_get_snap_context(struct ceph_snap_context *sc)
+{
+       if (sc)
+               atomic_inc(&sc->nref);
+       return sc;
+}
+EXPORT_SYMBOL(ceph_get_snap_context);
+
+void ceph_put_snap_context(struct ceph_snap_context *sc)
+{
+       if (!sc)
+               return;
+       if (atomic_dec_and_test(&sc->nref)) {
+               /*printk(" deleting snap_context %p\n", sc);*/
+               kfree(sc);
+       }
+}
+EXPORT_SYMBOL(ceph_put_snap_context);