md-cache: meta-data caching translator

This is a metadata caching translator which is well integrated with
glusterfs core framework and leverages some of the recent protocol
changes to do a better job at caching.

- It uses the attributes returned along callbacks of all calls to
  update its attribute cache as frequently as possible without
  issuing calls on its own (i.e, very low overhead)

- It caches attributes returned via readdirp into the inode contexts
  corresponding to those entries (i.e, well integrated)

- It caches and updates xattrs and not just inode attributes (i.e,
  eliminates the need for a separate xattr-prefetch translator)

In its current form it has a timeout based consistency model

Change-Id: I891f6225c1a4c08bb111e287571d5f6d326dbe97
BUG: 765785
Reviewed-on: http://review.gluster.com/2713
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

3 files changed, 1811 insertions, 0 deletions

diff --git a/xlators/performance/md-cache/src/Makefile.am b/xlators/performance/md-cache/src/Makefile.am
new file mode 100644
index 00000000000..6031c223fa9
--- /dev/null
+++ b/xlators/performance/md-cache/src/Makefile.am
@@ -0,0 +1,14 @@
+xlator_LTLIBRARIES = md-cache.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+md_cache_la_LDFLAGS = -module -avoidversion
+
+md_cache_la_SOURCES = md-cache.c
+md_cache_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+noinst_HEADERS = md-cache-mem-types.h
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS) \
+	-I$(top_srcdir)/libglusterfs/src -I$(CONTRIBDIR)/rbtree -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES =
diff --git a/xlators/performance/md-cache/src/md-cache-mem-types.h b/xlators/performance/md-cache/src/md-cache-mem-types.h
new file mode 100644
index 00000000000..f09e882573c
--- /dev/null
+++ b/xlators/performance/md-cache/src/md-cache-mem-types.h
@@ -0,0 +1,33 @@
+/*
+   Copyright (c) 2012 Red Hat, Inc. <http://www.redhat.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS 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, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef __MDC_MEM_TYPES_H__
+#define __MDC_MEM_TYPES_H__
+
+#include "mem-types.h"
+
+enum gf_mdc_mem_types_ {
+        gf_mdc_mt_mdc_local_t   = gf_common_mt_end + 1,
+	gf_mdc_mt_md_cache_t,
+	gf_mdc_mt_mdc_conf_t,
+        gf_mdc_mt_end
+};
+#endif
+
diff --git a/xlators/performance/md-cache/src/md-cache.c b/xlators/performance/md-cache/src/md-cache.c
new file mode 100644
index 00000000000..dd9a8d6d09a
--- /dev/null
+++ b/xlators/performance/md-cache/src/md-cache.c
@@ -0,0 +1,1764 @@
+/*
+  Copyright (c) 2012 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS 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, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "md-cache-mem-types.h"
+#include <assert.h>
+#include <sys/time.h>
+
+
+/* TODO:
+   - cache symlink() link names and nuke symlink-cache
+   - send proper postbuf in setattr_cbk even when op_ret = -1
+*/
+
+
+struct mdc_conf {
+	int  timeout;
+};
+
+
+struct mdc_key {
+	const char *name;
+	int         load;
+	int         check;
+} mdc_keys[] = {
+	{
+		.name = "system.posix_acl_access",
+		.load = 1,
+		.check = 1,
+	},
+	{
+		.name = "system.posix_acl_default",
+		.load = 1,
+		.check = 1,
+	},
+	{
+		.name = "security.selinux",
+		.load = 1,
+		.check = 1,
+	},
+	{
+		.name = "security.capability",
+		.load = 1,
+		.check = 1,
+	},
+	{
+		.name = "gfid-req",
+		.load = 0,
+		.check = 1,
+	},
+	{},
+};
+
+
+static uint64_t
+gfid_to_ino (uuid_t gfid)
+{
+	uint64_t  ino = 0;
+	int       i = 0, j = 0;
+
+        for (i = 15; i > (15 - 8); i--) {
+                ino += (uint64_t)(gfid[i]) << j;
+                j += 8;
+        }
+
+	return ino;
+}
+
+
+struct mdc_local;
+typedef struct mdc_local mdc_local_t;
+
+#define MDC_STACK_UNWIND(fop, frame, params ...) do {           \
+                mdc_local_t *__local = NULL;                    \
+                xlator_t    *__xl    = NULL;                    \
+                if (frame) {                                    \
+                        __xl         = frame->this;             \
+                        __local      = frame->local;            \
+                        frame->local = NULL;                    \
+                }                                               \
+                STACK_UNWIND_STRICT (fop, frame, params);       \
+                mdc_local_wipe (__xl, __local);                 \
+        } while (0)
+
+
+struct md_cache {
+        ia_prot_t     md_prot;
+        uint32_t      md_nlink;
+        uint32_t      md_uid;
+        uint32_t      md_gid;
+        uint32_t      md_atime;
+        uint32_t      md_atime_nsec;
+        uint32_t      md_mtime;
+        uint32_t      md_mtime_nsec;
+        uint32_t      md_ctime;
+        uint32_t      md_ctime_nsec;
+        uint64_t      md_rdev;
+        uint64_t      md_size;
+        uint64_t      md_blocks;
+        dict_t       *xattr;
+        char         *linkname;
+	time_t        ia_time;
+	time_t        xa_time;
+};
+
+
+struct mdc_local {
+        loc_t     loc;
+        loc_t     loc2;
+        fd_t     *fd;
+        char     *linkname;
+        dict_t   *xattr;
+};
+
+
+int
+__mdc_inode_ctx_get (xlator_t *this, inode_t *inode, struct md_cache **mdc_p)
+{
+        int              ret = 0;
+        struct md_cache *mdc = NULL;
+        uint64_t         mdc_int = 0;
+
+	ret = __inode_ctx_get (inode, this, &mdc_int);
+	mdc = (void *) (long) (mdc_int);
+	if (ret == 0 && mdc_p)
+		*mdc_p = mdc;
+
+	return ret;
+}
+
+
+int
+mdc_inode_ctx_get (xlator_t *this, inode_t *inode, struct md_cache **mdc_p)
+{
+	int   ret;
+
+	LOCK(&inode->lock);
+	{
+		ret = __mdc_inode_ctx_get (this, inode, mdc_p);
+	}
+	UNLOCK(&inode->lock);
+
+	return ret;
+}
+
+
+int
+__mdc_inode_ctx_set (xlator_t *this, inode_t *inode, struct md_cache *mdc)
+{
+        int              ret = 0;
+        uint64_t         mdc_int = 0;
+
+	mdc_int = (long) mdc;
+	ret = __inode_ctx_set2 (inode, this, &mdc_int, 0);
+
+	return ret;
+}
+
+
+int
+mdc_inode_ctx_set (xlator_t *this, inode_t *inode, struct md_cache *mdc)
+{
+	int   ret;
+
+	LOCK(&inode->lock);
+	{
+		ret = __mdc_inode_ctx_set (this, inode, mdc);
+	}
+	UNLOCK(&inode->lock);
+
+	return ret;
+}
+
+
+mdc_local_t *
+mdc_local_get (call_frame_t *frame)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+        if (local)
+                goto out;
+
+        local = GF_CALLOC (sizeof (*local), 1, gf_mdc_mt_mdc_local_t);
+        if (!local)
+                goto out;
+
+        frame->local = local;
+out:
+        return local;
+}
+
+
+void
+mdc_local_wipe (xlator_t *this, mdc_local_t *local)
+{
+        if (!local)
+                return;
+
+        loc_wipe (&local->loc);
+
+        loc_wipe (&local->loc2);
+
+        if (local->fd)
+                fd_unref (local->fd);
+
+        if (local->linkname)
+                GF_FREE (local->linkname);
+
+        if (local->xattr)
+                dict_unref (local->xattr);
+
+        GF_FREE (local);
+        return;
+}
+
+
+int
+mdc_inode_wipe (xlator_t *this, inode_t *inode)
+{
+        int              ret = 0;
+        uint64_t         mdc_int = 0;
+        struct md_cache *mdc = NULL;
+
+        ret = inode_ctx_del (inode, this, &mdc_int);
+        if (ret != 0)
+                goto out;
+
+        mdc = (void *) (long) mdc_int;
+
+        if (mdc->xattr)
+                dict_unref (mdc->xattr);
+
+        if (mdc->linkname)
+                GF_FREE (mdc->linkname);
+
+        GF_FREE (mdc);
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+struct md_cache *
+mdc_inode_prep (xlator_t *this, inode_t *inode)
+{
+        int              ret = 0;
+        struct md_cache *mdc = NULL;
+
+        LOCK (&inode->lock);
+        {
+		ret = __mdc_inode_ctx_get (this, inode, &mdc);
+                if (ret == 0)
+                        goto unlock;
+
+                mdc = GF_CALLOC (sizeof (*mdc), 1, gf_mdc_mt_md_cache_t);
+                if (!mdc) {
+                        gf_log (this->name, GF_LOG_ERROR,
+                                "out of memory :(");
+                        goto unlock;
+                }
+
+                ret = __mdc_inode_ctx_set (this, inode, mdc);
+                if (ret) {
+                        gf_log (this->name, GF_LOG_ERROR,
+                                "out of memory :(");
+                        GF_FREE (mdc);
+                        mdc = NULL;
+                }
+        }
+unlock:
+        UNLOCK (&inode->lock);
+
+        return mdc;
+}
+
+
+static gf_boolean_t
+is_md_cache_iatt_valid (xlator_t *this, struct md_cache *mdc)
+{
+	struct mdc_conf *conf = NULL;
+	time_t           now = 0;
+
+	conf = this->private;
+
+	time (&now);
+
+	if (now > (mdc->ia_time + conf->timeout))
+		return _gf_false;
+
+	return _gf_true;
+}
+
+
+static gf_boolean_t
+is_md_cache_xatt_valid (xlator_t *this, struct md_cache *mdc)
+{
+	struct mdc_conf *conf = NULL;
+	time_t           now = 0;
+
+	conf = this->private;
+
+	time (&now);
+
+	if (now > (mdc->xa_time + conf->timeout))
+		return _gf_false;
+
+	return _gf_true;
+}
+
+
+void
+mdc_from_iatt (struct md_cache *mdc, struct iatt *iatt)
+{
+        mdc->md_prot       = iatt->ia_prot;
+        mdc->md_nlink      = iatt->ia_nlink;
+        mdc->md_uid        = iatt->ia_uid;
+        mdc->md_gid        = iatt->ia_gid;
+        mdc->md_atime      = iatt->ia_atime;
+        mdc->md_atime_nsec = iatt->ia_atime_nsec;
+        mdc->md_mtime      = iatt->ia_mtime;
+        mdc->md_mtime_nsec = iatt->ia_mtime_nsec;
+        mdc->md_ctime      = iatt->ia_ctime;
+        mdc->md_ctime_nsec = iatt->ia_ctime_nsec;
+        mdc->md_rdev       = iatt->ia_rdev;
+        mdc->md_size       = iatt->ia_size;
+        mdc->md_blocks     = iatt->ia_blocks;
+}
+
+
+void
+mdc_to_iatt (struct md_cache *mdc, struct iatt *iatt)
+{
+        iatt->ia_prot       = mdc->md_prot;
+        iatt->ia_nlink      = mdc->md_nlink;
+        iatt->ia_uid        = mdc->md_uid;
+        iatt->ia_gid        = mdc->md_gid;
+        iatt->ia_atime      = mdc->md_atime;
+        iatt->ia_atime_nsec = mdc->md_atime_nsec;
+        iatt->ia_mtime      = mdc->md_mtime;
+        iatt->ia_mtime_nsec = mdc->md_mtime_nsec;
+        iatt->ia_ctime      = mdc->md_ctime;
+        iatt->ia_ctime_nsec = mdc->md_ctime_nsec;
+        iatt->ia_rdev       = mdc->md_rdev;
+        iatt->ia_size       = mdc->md_size;
+        iatt->ia_blocks     = mdc->md_blocks;
+}
+
+
+int
+mdc_inode_iatt_set (xlator_t *this, inode_t *inode, struct iatt *iatt)
+{
+        int              ret = -1;
+        struct md_cache *mdc = NULL;
+
+        mdc = mdc_inode_prep (this, inode);
+        if (!mdc)
+                goto out;
+
+        if (!iatt || !iatt->ia_ctime) {
+		mdc->ia_time = 0;
+                return 0;
+	}
+
+        mdc_from_iatt (mdc, iatt);
+
+	time (&mdc->ia_time);
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+int
+mdc_inode_iatt_get (xlator_t *this, inode_t *inode, struct iatt *iatt)
+{
+        int              ret = -1;
+        struct md_cache *mdc = NULL;
+
+        if (mdc_inode_ctx_get (this, inode, &mdc) != 0)
+                goto out;
+
+	if (!is_md_cache_iatt_valid (this, mdc))
+		goto out;
+
+        mdc_to_iatt (mdc, iatt);
+
+        uuid_copy (iatt->ia_gfid, inode->gfid);
+        iatt->ia_ino    = gfid_to_ino (inode->gfid);
+        iatt->ia_dev    = 42;
+        iatt->ia_type   = inode->ia_type;
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+int
+mdc_inode_xatt_set (xlator_t *this, inode_t *inode, dict_t *dict)
+{
+        int              ret = -1;
+        struct md_cache *mdc = NULL;
+
+        mdc = mdc_inode_prep (this, inode);
+        if (!mdc)
+                goto out;
+
+        if (!dict)
+                goto out;
+
+        if (mdc->xattr)
+                dict_unref (mdc->xattr);
+
+        mdc->xattr = dict_ref (dict);
+
+	time (&mdc->xa_time);
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+int
+mdc_inode_xatt_update (xlator_t *this, inode_t *inode, dict_t *dict)
+{
+        int              ret = -1;
+        struct md_cache *mdc = NULL;
+
+        mdc = mdc_inode_prep (this, inode);
+        if (!mdc)
+                goto out;
+
+        if (!dict)
+                goto out;
+
+        if (!mdc->xattr)
+                mdc->xattr = dict_ref (dict);
+        else
+                dict_copy (dict, mdc->xattr);
+
+        mdc->xattr = dict_ref (dict);
+
+	time (&mdc->xa_time);
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+int
+mdc_inode_xatt_get (xlator_t *this, inode_t *inode, dict_t **dict)
+{
+        int              ret = -1;
+        struct md_cache *mdc = NULL;
+
+        if (mdc_inode_ctx_get (this, inode, &mdc) != 0)
+                goto out;
+
+	if (!is_md_cache_xatt_valid (this, mdc))
+		goto out;
+
+        if (!mdc->xattr)
+                goto out;
+
+        if (dict)
+                *dict = dict_ref (mdc->xattr);
+
+        ret = 0;
+out:
+        return ret;
+}
+
+
+void
+mdc_load_reqs (xlator_t *this, dict_t *dict)
+{
+	const char *mdc_key = NULL;
+	int  i = 0;
+	int  ret = 0;
+
+	for (mdc_key = mdc_keys[i].name; (mdc_key = mdc_keys[i].name); i++) {
+		if (!mdc_keys[i].load)
+			continue;
+		ret = dict_set_int8 (dict, (char *)mdc_key, 0);
+		if (ret)
+			return;
+	}
+}
+
+
+struct checkpair {
+	int  ret;
+	dict_t *rsp;
+};
+
+
+static int
+is_mdc_key_satisfied (const char *key)
+{
+	const char *mdc_key = NULL;
+	int  i = 0;
+
+	if (!key)
+		return 0;
+
+	for (mdc_key = mdc_keys[i].name; (mdc_key = mdc_keys[i].name); i++) {
+		if (!mdc_keys[i].check)
+			continue;
+		if (strcmp (mdc_key, key) == 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+
+static void
+checkfn (dict_t *this, char *key, data_t *value, void *data)
+{
+        struct checkpair *pair = data;
+
+	if (!is_mdc_key_satisfied (key))
+		pair->ret = 0;
+}
+
+
+int
+mdc_xattr_satisfied (xlator_t *this, dict_t *req, dict_t *rsp)
+{
+        struct checkpair pair = {
+                .ret = 1,
+                .rsp = rsp,
+        };
+
+        dict_foreach (req, checkfn, &pair);
+
+        return pair.ret;
+}
+
+
+int
+mdc_lookup_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret,	int32_t op_errno, inode_t *inode,
+                struct iatt *stbuf, dict_t *dict, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, stbuf);
+                mdc_inode_xatt_set (this, local->loc.inode, dict);
+        }
+out:
+        MDC_STACK_UNWIND (lookup, frame, op_ret, op_errno, inode, stbuf,
+                          dict, postparent);
+        return 0;
+}
+
+
+int
+mdc_lookup (call_frame_t *frame, xlator_t *this, loc_t *loc,
+            dict_t *xattr_req)
+{
+        int          ret = 0;
+        struct iatt  stbuf = {0, };
+        struct iatt  postparent = {0, };
+        dict_t      *xattr_rsp = NULL;
+        mdc_local_t *local = NULL;
+
+
+        local = mdc_local_get (frame);
+        if (!local)
+                goto uncached;
+
+        loc_copy (&local->loc, loc);
+
+        ret = mdc_inode_iatt_get (this, loc->inode, &stbuf);
+        if (ret != 0)
+                goto uncached;
+
+        if (xattr_req) {
+                ret = mdc_inode_xatt_get (this, loc->inode, &xattr_rsp);
+                if (ret != 0)
+                        goto uncached;
+
+                if (!mdc_xattr_satisfied (this, xattr_req, xattr_rsp))
+                        goto uncached;
+        }
+
+        MDC_STACK_UNWIND (lookup, frame, 0, 0, loc->inode, &stbuf,
+                          xattr_rsp, &postparent);
+
+        if (xattr_rsp)
+                dict_unref (xattr_rsp);
+
+        return 0;
+
+uncached:
+	if (xattr_req)
+		mdc_load_reqs (this, xattr_req);
+
+        STACK_WIND (frame, mdc_lookup_cbk, FIRST_CHILD (this),
+                    FIRST_CHILD (this)->fops->lookup, loc, xattr_req);
+
+        if (xattr_rsp)
+                dict_unref (xattr_rsp);
+
+        return 0;
+}
+
+
+int
+mdc_stat_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+              int32_t op_ret, int32_t op_errno, struct iatt *buf)
+{
+        mdc_local_t  *local = NULL;
+
+        if (op_ret != 0)
+                goto out;
+
+        local = frame->local;
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->loc.inode, buf);
+
+out:
+        MDC_STACK_UNWIND (stat, frame, op_ret, op_errno, buf);
+
+        return 0;
+}
+
+
+int
+mdc_stat (call_frame_t *frame, xlator_t *this, loc_t *loc)
+{
+        int           ret;
+        struct iatt   stbuf;
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+        if (!local)
+                goto uncached;
+
+        loc_copy (&local->loc, loc);
+
+        ret = mdc_inode_iatt_get (this, loc->inode, &stbuf);
+        if (ret != 0)
+                goto uncached;
+
+        MDC_STACK_UNWIND (stat, frame, 0, 0, &stbuf);
+
+        return 0;
+
+uncached:
+        STACK_WIND (frame, mdc_stat_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->stat,
+                    loc);
+        return 0;
+}
+
+
+int
+mdc_fstat_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno, struct iatt *buf)
+{
+        mdc_local_t  *local = NULL;
+
+        if (op_ret != 0)
+                goto out;
+
+        local = frame->local;
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, buf);
+
+out:
+        MDC_STACK_UNWIND (fstat, frame, op_ret, op_errno, buf);
+
+        return 0;
+}
+
+
+int
+mdc_fstat (call_frame_t *frame, xlator_t *this, fd_t *fd)
+{
+        int           ret;
+        struct iatt   stbuf;
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+        if (!local)
+                goto uncached;
+
+        local->fd = fd_ref (fd);
+
+        ret = mdc_inode_iatt_get (this, fd->inode, &stbuf);
+        if (ret != 0)
+                goto uncached;
+
+        MDC_STACK_UNWIND (fstat, frame, 0, 0, &stbuf);
+
+        return 0;
+
+uncached:
+        STACK_WIND (frame, mdc_fstat_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->fstat,
+                    fd);
+        return 0;
+}
+
+
+int
+mdc_truncate_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                  int32_t op_ret, int32_t op_errno,
+                  struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->loc.inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (truncate, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_truncate (call_frame_t *frame, xlator_t *this, loc_t *loc,
+              off_t offset)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->loc.inode = inode_ref (loc->inode);
+
+        STACK_WIND (frame, mdc_truncate_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->truncate,
+                    loc, offset);
+        return 0;
+}
+
+
+int
+mdc_ftruncate_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                   int32_t op_ret, int32_t op_errno,
+                   struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (ftruncate, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_ftruncate (call_frame_t *frame, xlator_t *this, fd_t *fd,
+               off_t offset)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+        STACK_WIND (frame, mdc_ftruncate_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->ftruncate,
+                    fd, offset);
+        return 0;
+}
+
+
+int
+mdc_mknod_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno, inode_t *inode,
+               struct iatt *buf, struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, buf);
+                mdc_inode_xatt_set (this, local->loc.inode, local->xattr);
+        }
+out:
+        MDC_STACK_UNWIND (mknod, frame, op_ret, op_errno, inode, buf,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_mknod (call_frame_t *frame, xlator_t *this, loc_t *loc,
+           mode_t mode, dev_t rdev, dict_t *params)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+        local->xattr = dict_ref (params);
+
+        STACK_WIND (frame, mdc_mknod_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->mknod,
+                    loc, mode, rdev, params);
+        return 0;
+}
+
+
+int
+mdc_mkdir_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno, inode_t *inode,
+               struct iatt *buf, struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, buf);
+                mdc_inode_xatt_set (this, local->loc.inode, local->xattr);
+        }
+out:
+        MDC_STACK_UNWIND (mkdir, frame, op_ret, op_errno, inode, buf,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_mkdir (call_frame_t *frame, xlator_t *this, loc_t *loc,
+           mode_t mode, dict_t *params)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+        local->xattr = dict_ref (params);
+
+        STACK_WIND (frame, mdc_mkdir_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->mkdir,
+                    loc, mode, params);
+        return 0;
+}
+
+
+int
+mdc_unlink_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret, int32_t op_errno,
+                struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, NULL);
+        }
+
+out:
+        MDC_STACK_UNWIND (unlink, frame, op_ret, op_errno,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_unlink (call_frame_t *frame, xlator_t *this, loc_t *loc)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+
+        STACK_WIND (frame, mdc_unlink_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->unlink,
+                    loc);
+        return 0;
+}
+
+
+int
+mdc_rmdir_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret, int32_t op_errno,
+                struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+out:
+        MDC_STACK_UNWIND (rmdir, frame, op_ret, op_errno,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_rmdir (call_frame_t *frame, xlator_t *this, loc_t *loc, int flag)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+
+        STACK_WIND (frame, mdc_rmdir_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->rmdir,
+                    loc, flag);
+        return 0;
+}
+
+
+int
+mdc_symlink_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                 int32_t op_ret, int32_t op_errno, inode_t *inode,
+                 struct iatt *buf, struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, buf);
+        }
+out:
+        MDC_STACK_UNWIND (symlink, frame, op_ret, op_errno, inode, buf,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_symlink (call_frame_t *frame, xlator_t *this, const char *linkname,
+             loc_t *loc, dict_t *params)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+
+        local->linkname = strdup (linkname);
+
+        STACK_WIND (frame, mdc_symlink_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->symlink,
+                    linkname, loc, params);
+        return 0;
+}
+
+
+int
+mdc_rename_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret, int32_t op_errno, struct iatt *buf,
+                struct iatt *preoldparent, struct iatt *postoldparent,
+                struct iatt *prenewparent, struct iatt *postnewparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postoldparent);
+        }
+
+        if (local->loc.inode) {
+		/* TODO: fix dht_rename() not to return linkfile
+		   attributes before setting attributes here
+		*/
+
+		mdc_inode_iatt_set (this, local->loc.inode, NULL);
+        }
+
+        if (local->loc2.parent) {
+                mdc_inode_iatt_set (this, local->loc2.parent, postnewparent);
+        }
+out:
+        MDC_STACK_UNWIND (rename, frame, op_ret, op_errno, buf,
+                          preoldparent, postoldparent, prenewparent, postnewparent);
+        return 0;
+}
+
+
+int
+mdc_rename (call_frame_t *frame, xlator_t *this,
+            loc_t *oldloc, loc_t *newloc)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, oldloc);
+        loc_copy (&local->loc2, newloc);
+
+        STACK_WIND (frame, mdc_rename_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->rename,
+                    oldloc, newloc);
+        return 0;
+}
+
+
+int
+mdc_link_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+              int32_t op_ret, int32_t op_errno, inode_t *inode, struct iatt *buf,
+              struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, local->loc.inode, buf);
+        }
+
+        if (local->loc2.parent) {
+                mdc_inode_iatt_set (this, local->loc2.parent, postparent);
+        }
+out:
+        MDC_STACK_UNWIND (link, frame, op_ret, op_errno, inode, buf,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_link (call_frame_t *frame, xlator_t *this,
+          loc_t *oldloc, loc_t *newloc)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, oldloc);
+        loc_copy (&local->loc2, newloc);
+
+        STACK_WIND (frame, mdc_link_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->link,
+                    oldloc, newloc);
+        return 0;
+}
+
+
+int
+mdc_create_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret, int32_t op_errno, fd_t *fd, inode_t *inode,
+                struct iatt *buf, struct iatt *preparent, struct iatt *postparent)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        if (local->loc.parent) {
+                mdc_inode_iatt_set (this, local->loc.parent, postparent);
+        }
+
+        if (local->loc.inode) {
+                mdc_inode_iatt_set (this, inode, buf);
+                mdc_inode_xatt_set (this, local->loc.inode, local->xattr);
+        }
+out:
+        MDC_STACK_UNWIND (create, frame, op_ret, op_errno, fd, inode, buf,
+                          preparent, postparent);
+        return 0;
+}
+
+
+int
+mdc_create (call_frame_t *frame, xlator_t *this, loc_t *loc, int flags,
+            mode_t mode, fd_t *fd, dict_t *params)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+        local->xattr = dict_ref (params);
+
+        STACK_WIND (frame, mdc_create_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->create,
+                    loc, flags, mode, fd, params);
+        return 0;
+}
+
+
+int
+mdc_readv_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno,
+               struct iovec *vector, int32_t count,
+               struct iatt *stbuf, struct iobref *iobref)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, stbuf);
+
+out:
+        MDC_STACK_UNWIND (readv, frame, op_ret, op_errno, vector, count,
+                          stbuf, iobref);
+
+        return 0;
+}
+
+
+int
+mdc_readv (call_frame_t *frame, xlator_t *this, fd_t *fd, size_t size,
+           off_t offset, uint32_t flags)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+        STACK_WIND (frame, mdc_readv_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->readv,
+                    fd, size, offset, flags);
+        return 0;
+}
+
+
+int
+mdc_writev_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno,
+               struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret == -1)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (writev, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_writev (call_frame_t *frame, xlator_t *this, fd_t *fd, struct iovec *vector,
+            int count, off_t offset, uint32_t flags, struct iobref *iobref)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+        STACK_WIND (frame, mdc_writev_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->writev,
+                    fd, vector, count, offset, flags, iobref);
+        return 0;
+}
+
+
+int
+mdc_setattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                 int32_t op_ret, int32_t op_errno,
+                 struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0) {
+		mdc_inode_iatt_set (this, local->loc.inode, NULL);
+                goto out;
+	}
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->loc.inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (setattr, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_setattr (call_frame_t *frame, xlator_t *this, loc_t *loc,
+             struct iatt *stbuf, int valid)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+
+        STACK_WIND (frame, mdc_setattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->setattr,
+                    loc, stbuf, valid);
+        return 0;
+}
+
+
+int
+mdc_fsetattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                  int32_t op_ret, int32_t op_errno,
+                  struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (fsetattr, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_fsetattr (call_frame_t *frame, xlator_t *this, fd_t *fd,
+              struct iatt *stbuf, int valid)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+        STACK_WIND (frame, mdc_setattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->fsetattr,
+                    fd, stbuf, valid);
+        return 0;
+}
+
+
+int
+mdc_fsync_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno,
+               struct iatt *prebuf, struct iatt *postbuf)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_iatt_set (this, local->fd->inode, postbuf);
+
+out:
+        MDC_STACK_UNWIND (fsync, frame, op_ret, op_errno, prebuf, postbuf);
+
+        return 0;
+}
+
+
+int
+mdc_fsync (call_frame_t *frame, xlator_t *this, fd_t *fd, int datasync)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+        STACK_WIND (frame, mdc_fsync_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->fsync,
+                    fd, datasync);
+        return 0;
+}
+
+
+int
+mdc_setxattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                  int32_t op_ret, int32_t op_errno)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_xatt_update (this, local->loc.inode, local->xattr);
+
+out:
+        MDC_STACK_UNWIND (setxattr, frame, op_ret, op_errno);
+
+        return 0;
+}
+
+
+int
+mdc_setxattr (call_frame_t *frame, xlator_t *this, loc_t *loc,
+              dict_t *xattr, int flags)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+        loc_copy (&local->loc, loc);
+        local->xattr = dict_ref (xattr);
+
+        STACK_WIND (frame, mdc_setxattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->setxattr,
+                    loc, xattr, flags);
+        return 0;
+}
+
+
+int
+mdc_fsetxattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+		   int32_t op_ret, int32_t op_errno)
+{
+        mdc_local_t  *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret != 0)
+                goto out;
+
+        if (!local)
+                goto out;
+
+        mdc_inode_xatt_update (this, local->fd->inode, local->xattr);
+
+out:
+        MDC_STACK_UNWIND (fsetxattr, frame, op_ret, op_errno);
+
+        return 0;
+}
+
+
+int
+mdc_fsetxattr (call_frame_t *frame, xlator_t *this, fd_t *fd,
+	       dict_t *xattr, int flags)
+{
+        mdc_local_t  *local = NULL;
+
+        local = mdc_local_get (frame);
+
+	local->fd = fd_ref (fd);
+        local->xattr = dict_ref (xattr);
+
+        STACK_WIND (frame, mdc_fsetxattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->fsetxattr,
+                    fd, xattr, flags);
+        return 0;
+}
+
+int
+mdc_getxattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+		  int32_t op_ret, int32_t op_errno, dict_t *xattr)
+{
+        mdc_local_t  *local = NULL;
+
+        if (op_ret != 0)
+                goto out;
+
+        local = frame->local;
+        if (!local)
+                goto out;
+
+        mdc_inode_xatt_update (this, local->loc.inode, xattr);
+
+out:
+        MDC_STACK_UNWIND (getxattr, frame, op_ret, op_errno, xattr);
+
+        return 0;
+}
+
+
+int
+mdc_getxattr (call_frame_t *frame, xlator_t *this, loc_t *loc, const char *key)
+{
+        int           ret;
+        mdc_local_t  *local = NULL;
+	dict_t       *xattr = NULL;
+
+        local = mdc_local_get (frame);
+        if (!local)
+                goto uncached;
+
+        loc_copy (&local->loc, loc);
+
+	if (!is_mdc_key_satisfied (key))
+		goto uncached;
+
+	ret = mdc_inode_xatt_get (this, loc->inode, &xattr);
+	if (ret != 0)
+		goto uncached;
+
+	if (!dict_get (xattr, (char *)key))
+		goto uncached;
+
+        MDC_STACK_UNWIND (getxattr, frame, 0, 0, xattr);
+
+        return 0;
+
+uncached:
+        STACK_WIND (frame, mdc_getxattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->getxattr,
+                    loc, key);
+        return 0;
+}
+
+
+int
+mdc_fgetxattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+		   int32_t op_ret, int32_t op_errno, dict_t *xattr)
+{
+        mdc_local_t  *local = NULL;
+
+        if (op_ret != 0)
+                goto out;
+
+        local = frame->local;
+        if (!local)
+                goto out;
+
+        mdc_inode_xatt_update (this, local->fd->inode, xattr);
+
+out:
+        MDC_STACK_UNWIND (fgetxattr, frame, op_ret, op_errno, xattr);
+
+        return 0;
+}
+
+
+int
+mdc_fgetxattr (call_frame_t *frame, xlator_t *this, fd_t *fd, const char *key)
+{
+        int           ret;
+        mdc_local_t  *local = NULL;
+	dict_t       *xattr = NULL;
+
+        local = mdc_local_get (frame);
+        if (!local)
+                goto uncached;
+
+        local->fd = fd_ref (fd);
+
+	if (!is_mdc_key_satisfied (key))
+		goto uncached;
+
+	ret = mdc_inode_xatt_get (this, fd->inode, &xattr);
+	if (ret != 0)
+		goto uncached;
+
+	if (!dict_get (xattr, (char *)key))
+		goto uncached;
+
+        MDC_STACK_UNWIND (fgetxattr, frame, 0, 0, xattr);
+
+        return 0;
+
+uncached:
+        STACK_WIND (frame, mdc_fgetxattr_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->fgetxattr,
+                    fd, key);
+        return 0;
+}
+
+
+int
+mdc_readdirp_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+		  int op_ret, int op_errno, gf_dirent_t *entries)
+{
+        gf_dirent_t *entry      = NULL;
+
+	if (op_ret <= 0)
+		goto unwind;
+
+        list_for_each_entry (entry, &entries->list, list) {
+                if (!entry->inode)
+			continue;
+                mdc_inode_iatt_set (this, entry->inode, &entry->d_stat);
+                mdc_inode_xatt_set (this, entry->inode, entry->dict);
+        }
+
+unwind:
+	STACK_UNWIND_STRICT (readdirp, frame, op_ret, op_errno, entries);
+	return 0;
+}
+
+
+int
+mdc_readdirp (call_frame_t *frame, xlator_t *this, fd_t *fd,
+	      size_t size, off_t offset, dict_t *xattr_req)
+{
+	STACK_WIND (frame, mdc_readdirp_cbk,
+		    FIRST_CHILD (this), FIRST_CHILD (this)->fops->readdirp,
+		    fd, size, offset, xattr_req);
+	return 0;
+}
+
+
+int
+mdc_readdir (call_frame_t *frame, xlator_t *this, fd_t *fd,
+	     size_t size, off_t offset)
+{
+	dict_t *xattr_req = NULL;
+
+	xattr_req = dict_new ();
+
+	if (xattr_req) {
+		mdc_load_reqs (this, xattr_req);
+	}
+
+	STACK_WIND (frame, mdc_readdirp_cbk,
+		    FIRST_CHILD (this), FIRST_CHILD (this)->fops->readdirp,
+		    fd, size, offset, xattr_req);
+	return 0;
+}
+
+
+int
+mdc_forget (xlator_t *this, inode_t *inode)
+{
+        mdc_inode_wipe (this, inode);
+
+        return 0;
+}
+
+
+int
+reconfigure (xlator_t *this, dict_t *options)
+{
+	struct mdc_conf *conf = NULL;
+
+	conf = this->private;
+
+	GF_OPTION_RECONF ("timeout", conf->timeout, options, int32, out);
+out:
+	return 0;
+}
+
+
+int
+init (xlator_t *this)
+{
+	struct mdc_conf *conf = NULL;
+
+	conf = GF_CALLOC (sizeof (*conf), 1, gf_mdc_mt_mdc_conf_t);
+	if (!conf) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"out of memory");
+		return -1;
+	}
+
+        GF_OPTION_INIT ("timeout", conf->timeout, int32, out);
+
+out:
+	this->private = conf;
+
+        return 0;
+}
+
+
+void
+fini (xlator_t *this)
+{
+        return;
+}
+
+
+struct xlator_fops fops = {
+        .lookup      = mdc_lookup,
+        .stat        = mdc_stat,
+        .fstat       = mdc_fstat,
+        .truncate    = mdc_truncate,
+        .ftruncate   = mdc_ftruncate,
+        .mknod       = mdc_mknod,
+        .mkdir       = mdc_mkdir,
+        .unlink      = mdc_unlink,
+        .rmdir       = mdc_rmdir,
+        .symlink     = mdc_symlink,
+        .rename      = mdc_rename,
+        .link        = mdc_link,
+        .create      = mdc_create,
+        .readv       = mdc_readv,
+        .writev      = mdc_writev,
+        .setattr     = mdc_setattr,
+        .fsetattr    = mdc_fsetattr,
+        .fsync       = mdc_fsync,
+        .setxattr    = mdc_setxattr,
+        .fsetxattr   = mdc_fsetxattr,
+        .getxattr    = mdc_getxattr,
+        .fgetxattr   = mdc_fgetxattr,
+	.readdirp    = mdc_readdirp,
+	.readdir     = mdc_readdir
+};
+
+
+struct xlator_cbks cbks = {
+        .forget      = mdc_forget,
+};
+
+struct volume_options options[] = {
+        { .key = {"timeout"},
+          .type = GF_OPTION_TYPE_INT,
+          .min = 0,
+          .max = 60,
+          .default_value = "1",
+          .description = "Time period after which cache has to be refreshed",
+        },
+};