From 62ed8b36d67e073fd26c2c7353a8b7cc0961be20 Mon Sep 17 00:00:00 2001

From: Niels de Vos <ndevos@redhat.com>

Date: Sun, 31 May 2015 15:16:41 +0200

Subject: [PATCH 144/190] core: add "gf_ref_t" for common refcounting structures

This is a backport of http://review.gluster.org/#/c/11022/

There were errors from checkpatch.pl, it is fixed as part of

this backport, below are the changes:

added additional parenthesis for macro definition

    GF_REF_INIT

    GF_REF_GET

    GF_REF_PUT

> Checks for compiler supported atomic operations comes from client_t.h.

>

> An example usage of this change can be found in adding reference

> counting to "struct auth_cache_entry" in http://review.gluster.org/11023

>

> Basic usage looks like this:

>

>    #include "refcount.h"

>

>    struct my_struct {

>        GF_REF_DECL;

>        ... /* more members */

>    }

>

>    void my_destructor (void *data)

>    {

>        struct my_struct *my_ptr = (struct my_struct *) data;

>

>        ... /* do some more cleanups */

>        GF_FREE (my_ptr);

>    }

>

>    void init_ptr (struct parent *parent)

>    {

>        struct my_struct *my_ptr = malloc (sizeof (struct my_struct));

>

>        GF_REF_INIT (my_ptr, my_destructor); /* refcount is set to 1 */

>

>        ... /* my_ptr probably gets added to some parent structure */

>        parent_add_ptr (parent, my_ptr);

>    }

>

>    void do_something (struct parent *parent)

>    {

>        struct my_struct *my_ptr = NULL;

>

>        /* likely need to lock parent, depends on its access pattern */

>        my_ptr = parent_remove_first_ptr (parent);

>        /* unlock parent */

>

>        ... /* do something */

>

>        GF_REF_PUT (my_ptr); /* calls my_destructor on refcount = 0 */

>    }

>

> URL: http://thread.gmane.org/gmane.comp.file-systems.gluster.devel/11202

> Change-Id: Idb98a5861a44c31676108ed8876db12c320912ef

> BUG: 1228157

> Signed-off-by: Niels de Vos <ndevos@redhat.com>

> Reviewed-on: http://review.gluster.org/11022

> Reviewed-by: Xavier Hernandez <xhernandez@datalab.es>

> Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>

> Tested-by: Gluster Build System <jenkins@build.gluster.com>

> Tested-by: NetBSD Build System <jenkins@build.gluster.org>

Change-Id: I5630ff3fbd0e0021a83597d778e1037796be5355

BUG: 1235628

Signed-off-by: vmallika <vmallika@redhat.com>

Reviewed-on: https://code.engineering.redhat.com/gerrit/51605

Reviewed-by: Raghavendra Gowdappa <rgowdapp@redhat.com>

Tested-by: Raghavendra Gowdappa <rgowdapp@redhat.com>

---

 libglusterfs/src/Makefile.am |    4 +-

 libglusterfs/src/refcount.c  |  112 ++++++++++++++++++++++++++++++++++++++++++

 libglusterfs/src/refcount.h  |  103 ++++++++++++++++++++++++++++++++++++++

 3 files changed, 217 insertions(+), 2 deletions(-)

 create mode 100644 libglusterfs/src/refcount.c

 create mode 100644 libglusterfs/src/refcount.h

diff --git a/libglusterfs/src/Makefile.am b/libglusterfs/src/Makefile.am

index 80ce672..ed441d0 100644

--- a/libglusterfs/src/Makefile.am

+++ b/libglusterfs/src/Makefile.am

@@ -22,7 +22,7 @@ libglusterfs_la_SOURCES = dict.c xlator.c logging.c \

 	$(CONTRIBDIR)/rbtree/rb.c rbthash.c store.c latency.c \

 	graph.c syncop.c graph-print.c trie.c run.c options.c fd-lk.c \

 	circ-buff.c event-history.c gidcache.c ctx.c client_t.c event-poll.c \

-	event-epoll.c syncop-utils.c cluster-syncop.c \

+	event-epoll.c syncop-utils.c cluster-syncop.c refcount.c \

 	$(CONTRIBDIR)/libgen/basename_r.c \

 	$(CONTRIBDIR)/libgen/dirname_r.c $(CONTRIBDIR)/stdlib/gf_mkostemp.c \

 	strfd.c parse-utils.c $(CONTRIBDIR)/mount/mntent.c \

@@ -40,7 +40,7 @@ noinst_HEADERS = common-utils.h defaults.h dict.h glusterfs.h hashfn.h timespec.

 	gf-dirent.h locking.h syscall.h iobuf.h globals.h statedump.h \

 	checksum.h daemon.h $(CONTRIBDIR)/rbtree/rb.h store.h\

 	rbthash.h iatt.h latency.h mem-types.h syncop.h cluster-syncop.h \

-	graph-utils.h trie.h \

+	graph-utils.h trie.h refcount.h \

 	run.h options.h lkowner.h fd-lk.h circ-buff.h event-history.h \

 	gidcache.h client_t.h glusterfs-acl.h glfs-message-id.h \

 	template-component-messages.h strfd.h syncop-utils.h parse-utils.h \

diff --git a/libglusterfs/src/refcount.c b/libglusterfs/src/refcount.c

new file mode 100644

index 0000000..96edc10

--- /dev/null

+++ b/libglusterfs/src/refcount.c

@@ -0,0 +1,112 @@

+/*

+  Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>

+  This file is part of GlusterFS.

+

+  This file is licensed to you under your choice of the GNU Lesser

+  General Public License, version 3 or any later version (LGPLv3 or

+  later), or the GNU General Public License, version 2 (GPLv2), in all

+  cases as published by the Free Software Foundation.

+*/

+

+#include "common-utils.h"

+#include "refcount.h"

+

+#ifndef REFCOUNT_NEEDS_LOCK

+

+unsigned int

+_gf_ref_get (gf_ref_t *ref)

+{

+        unsigned int cnt = __sync_fetch_and_add (&ref->cnt, 1);

+

+        /* if cnt == 0, we're in a fatal position, the object will be free'd

+         *

+         * There is a race when two threads do a _gf_ref_get(). Only one of

+         * them may get a 0 returned. That is acceptible, because one

+         * _gf_ref_get() returning 0 should be handled as a fatal problem and

+         * when correct usage/locking is used, it should never happen.

+         */

+        GF_ASSERT (cnt != 0);

+

+        return cnt;

+}

+

+unsigned int

+_gf_ref_put (gf_ref_t *ref)

+{

+        unsigned int cnt = __sync_fetch_and_sub (&ref->cnt, 1);

+

+        /* if cnt == 1, the last user just did a _gf_ref_put()

+         *

+         * When cnt == 0, one _gf_ref_put() was done too much and there has

+         * been a thread using the refcounted structure when it was not

+         * supposed to.

+         */

+        GF_ASSERT (cnt != 0);

+

+        if (cnt == 1 && ref->release) {

+                ref->release (ref->data);

+                /* set return value to 0 to inform the caller correctly */

+                cnt = 0;

+        }

+

+        return cnt;

+}

+

+#else

+

+unsigned int

+_gf_ref_get (gf_ref_t *ref)

+{

+        unsigned int cnt = 0;

+

+        LOCK (&ref->lk);

+        {

+                /* never can be 0, should have been free'd */

+                if (ref->cnt > 0)

+                        cnt = ++ref->cnt;

+                else

+                        GF_ASSERT (ref->cnt > 0);

+        }

+        UNLOCK (&ref->lk);

+

+        return cnt;

+}

+

+unsigned int

+_gf_ref_put (gf_ref_t *ref)

+{

+        unsigned int cnt = 0;

+        int release = 0;

+

+        LOCK (&ref->lk);

+        {

+                if (ref->cnt != 0) {

+                        cnt = --ref->cnt;

+                        /* call release() only when cnt == 0 */

+                        release = (cnt == 0);

+                } else

+                        GF_ASSERT (ref->cnt != 0);

+        }

+        UNLOCK (&ref->lk);

+

+        if (release && ref->release)

+                ref->release (ref->data);

+

+        return cnt;

+}

+

+#endif /* REFCOUNT_NEEDS_LOCK */

+

+

+void

+_gf_ref_init (gf_ref_t *ref, gf_ref_release_t release, void *data)

+{

+        GF_ASSERT (ref);

+

+#ifdef REFCOUNT_NEEDS_LOCK

+        LOCK_INIT (&ref->lk);

+#endif

+        ref->cnt = 1;

+        ref->release = release;

+        ref->data = data;

+}

diff --git a/libglusterfs/src/refcount.h b/libglusterfs/src/refcount.h

new file mode 100644

index 0000000..c8113a2

--- /dev/null

+++ b/libglusterfs/src/refcount.h

@@ -0,0 +1,103 @@

+/*

+  Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>

+  This file is part of GlusterFS.

+

+  This file is licensed to you under your choice of the GNU Lesser

+  General Public License, version 3 or any later version (LGPLv3 or

+  later), or the GNU General Public License, version 2 (GPLv2), in all

+  cases as published by the Free Software Foundation.

+*/

+

+#ifndef _REFCOUNT_H

+#define _REFCOUNT_H

+

+/* check for compiler support for __sync_*_and_fetch()

+ *

+ * a more comprehensive feature test is shown at

+ * http://lists.iptel.org/pipermail/semsdev/2010-October/005075.html

+ * this is sufficient for RHEL5 i386 builds

+ */

+#if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)) && !defined(__i386__)

+#undef REFCOUNT_NEEDS_LOCK

+#else

+#define REFCOUNT_NEEDS_LOCK

+#include "locking.h"

+#endif /* compiler support for __sync_*_and_fetch() */

+

+typedef void (*gf_ref_release_t)(void *data);

+

+struct _gf_ref_t {

+#ifdef REFCOUNT_NEEDS_LOCK

+        gf_lock_t          lk;      /* lock for atomically adjust cnt */

+#endif

+        unsigned int       cnt;     /* number of users, free on 0 */

+

+        gf_ref_release_t   release; /* cleanup when cnt == 0 */

+        void              *data;    /* parameter passed to release() */

+};

+typedef struct _gf_ref_t gf_ref_t;

+

+

+/* _gf_ref_get -- increase the refcount and return the number of references

+ *

+ * @return: greater then 0 when a reference was taken, 0 when not

+ */

+unsigned int

+_gf_ref_get (gf_ref_t *ref);

+

+/* _gf_ref_put -- decrease the refcount and return the number of references

+ *

+ * @return: greater then 0 when there are still references, 0 when cleanup

+ *          should be done

+ */

+unsigned int

+_gf_ref_put (gf_ref_t *ref);

+

+/* _gf_ref_init -- initalize an embedded refcount object

+ *

+ * @release: function to call when the refcount == 0

+ * @data: parameter to be passed to @release

+ */

+void

+_gf_ref_init (gf_ref_t *ref, gf_ref_release_t release, void *data);

+

+

+/*

+ * Strong suggestion to use the simplified GF_REF_* API.

+ */

+

+/* GF_REF_DECL -- declaration to put inside your structure

+ *

+ * Example:

+ *   struct my_struct {

+ *       GF_REF_DECL;

+ *

+ *       ... // additional members

+ *   };

+ */

+#define GF_REF_DECL         gf_ref_t _ref

+

+/* GF_REF_INIT -- initialize a GF_REF_DECL structure

+ *

+ * @p: allocated structure with GF_REF_DECL

+ * @d: destructor to call once refcounting reaches 0

+ *

+ * Sets the refcount to 1.

+ */

+#define GF_REF_INIT(p, d)   (_gf_ref_init (&p->_ref, d, p))

+

+/* GF_REF_GET -- increase the refcount of a GF_REF_DECL structure

+ *

+ * @return: greater then 0 when a reference was taken, 0 when not

+ */

+#define GF_REF_GET(p)       (_gf_ref_get (&p->_ref))

+

+/* GF_REF_PUT -- decrease the refcount of a GF_REF_DECL structure

+ *

+ * @return: greater then 0 when there are still references, 0 when cleanup

+ *          should be done

+ */

+#define GF_REF_PUT(p)       (_gf_ref_put (&p->_ref))

+

+

+#endif /* _REFCOUNT_H */

-- 

1.7.1