rewriting stat-prefetch translator

- stat-prefetch aims to optimize operations like 'ls -l' where a readdir
   is immediately followed by stat calls on each of the directory entry read.
   More details on design can be found in doc/stat-prefetch-design.txt

Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 221 (stat prefetch implementation)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=221

6 files changed, 177 insertions, 499 deletions

diff --git a/configure.ac b/configure.ac
index 6a951096822..6fbaab2c852 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,6 +67,8 @@ AC_CONFIG_FILES([Makefile
 		xlators/performance/symlink-cache/src/Makefile
 		xlators/performance/quick-read/Makefile
 		xlators/performance/quick-read/src/Makefile
+                xlators/performance/stat-prefetch/Makefile
+                xlators/performance/stat-prefetch/src/Makefile
 		xlators/debug/Makefile
 		xlators/debug/trace/Makefile
 		xlators/debug/trace/src/Makefile
diff --git a/doc/stat-prefetch-design.txt b/doc/stat-prefetch-design.txt
new file mode 100644
index 00000000000..65f1b922705
--- /dev/null
+++ b/doc/stat-prefetch-design.txt
@@ -0,0 +1,128 @@
+what is stat-prefetch?
+======================
+It is a translator which caches the dentries read in readdir. This dentry
+list is stored in the context of fd. Later when lookup happens on 
+[parent-inode, basename (path)] combination, this list is searched for the
+basename. The dentry thus searched is used to fill up the stat corresponding
+to path being looked upon, thereby short-cutting lookup calls. This cache is
+preserved till closedir is called on the fd. The purpose of this translator 
+is to optimize operations like 'ls -l', where a readdir is followed by 
+lookup (stat) calls on each directory entry.
+
+1. stat-prefetch harnesses the efficiency of short lookup calls 
+   (saves network roundtrip time for lookup calls from being accounted to 
+   the stat call).
+2. To maintain the correctness, it does lookup-behind - lookup is winded to 
+   underlying translators after it is unwound to upper translators. 
+   A lookup-behind is necessary as inode gets populated in server inode table
+   only in lookup-cbk. Also various translators store their contexts in inode
+   contexts during lookup calls.
+
+fops to be implemented:
+======================
+* lookup
+  Check the dentry cache stored in context of fds opened by the same process 
+  on parent inode for basename. If found unwind with cached stat, else wind
+  the lookup call to underlying translators. We also store the stat path in 
+  context of inode if the path being looked upon happens to be directory. 
+  This stat will be used to fill postparent stat when lookup happens on any of
+  the directory contents.
+
+* readdir
+  Cache the direntries returned in readdir_cbk in the context of fd. If the 
+  readdir is happening on non-expected offsets (means a seekdir/rewinddir 
+  has happened), cache has to be flushed.
+
+* chmod/fchmod
+  Delete the entry corresponding to basename from cache stored in context of
+  fds opened on parent inode, since these calls change st_mode and ctime of 
+  stat.
+ 
+* chown/fchown
+  Delete the entry corresponding to basename from cache stored in context of 
+  fds opened on parent inode, since these calls change st_uid/st_gid and 
+  st_ctime of stat.
+
+* truncate/ftruncate
+  Delete the entry corresponding to basename from cache stored in context of 
+  fds opened on parent inode, since these calls change st_size/st_mtime of stat.
+
+* utimens
+  Delete the entry corresponding to basename from cache stored in context of 
+  fds opened on parent inode, since this call changes st_atime/st_mtime of stat.
+
+* readlink
+  Delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since this call changes st_atime of stat.
+ 
+* unlink
+  1. Delete the entry corresponding to basename from cache stored in context of 
+     fds opened on parent directory containing file being unlinked.
+  2. Delete the entry corresponding to basename of parent directory from cache
+     of its parent directory.
+
+* rmdir
+  1. Delete the entry corresponding to basename from cache stored in context of
+     fds opened on parent inode.
+  2. Remove the entire cache from all fds opened on inode corresponding to 
+     directory being removed.
+
+* readv
+  Delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since readv changes st_atime of file. 
+
+* writev
+  Delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since writev can possibly change st_size and definitely
+  changes st_mtime of file.
+
+* fsync
+  There is a confusion here as to whether fsync updates mtime/ctimes. Disk based
+  filesystems (atleast ext2) just writes the times stored in inode to disk 
+  during fsync and not the time at which fsync is being done. But in glusterfs, 
+  a translator like write-behind actually sends writes during fsync which will 
+  change mtime/ctime. Hence stat-prefetch implements fsync to delete the entry 
+  corresponding to basename from cache stored in context of fds opened on parent
+  inode.
+ 
+* rename
+  1. remove entry corresponding to oldname from cache stored in fd contexts of 
+     old parent directory.
+  2. remove entry corresponding to new parent directory from cache stored in
+     fd contexts of its parent directory.
+
+* create/mknod/mkdir/symlink/link
+  Delete entry corresponding to basename of directory in which these operations 
+  are happening, from cache stored in context of fds of parent directory. Note
+  that the parent directory containing the cahce is of the directory in which 
+  these operations are happening.
+
+* setxattr/removexattr
+  Delete the entry corresponding to basename from cache stored in context of fds
+  opened on parent inode, since setxattr changes st_ctime of file.
+
+* setdents/getdents/checksum/xattrop/fxattrop
+  These calls modify various times of stat structure, hence appropriate entries
+  have to be removed from the cache. I am leaving these calls unimplemented in 
+  stat-prefetch for timebeing. Once we have a working translator, these five fops
+  will be implemented.
+
+callbacks to be implemented:
+=======================
+* releasedir
+  Flush the stat-prefetch cache.
+
+* forget
+  Free the stat if the inode corresponds to a directory.
+
+limitations:
+============
+* since a readdir does not return extended attributes of file, if need_xattr is
+  set, short-cutting of lookup does not happen and lookup is passed to 
+  underlying translators.
+
+* posix_readdir does not check whether the dentries are spanning across multiple
+  mount points. Hence it is not transforming inode numbers in stat buffers if 
+  posix is configured to allow export directory spanning on multiple mountpoints.
+  This is a bug which needs to be fixed. posix_readdir should treat dentries the 
+  same way as if lookup is happening on dentries.
diff --git a/xlators/performance/Makefile.am b/xlators/performance/Makefile.am
index 6b5facca51e..e91d5f6efc8 100644
--- a/xlators/performance/Makefile.am
+++ b/xlators/performance/Makefile.am
@@ -1,3 +1,3 @@
-SUBDIRS = write-behind read-ahead io-threads io-cache symlink-cache quick-read
+SUBDIRS = write-behind read-ahead io-threads io-cache symlink-cache quick-read stat-prefetch
 
 CLEANFILES = 
diff --git a/xlators/performance/stat-prefetch/src/Makefile.am b/xlators/performance/stat-prefetch/src/Makefile.am
index e52f2df48fd..b16c133a1ab 100644
--- a/xlators/performance/stat-prefetch/src/Makefile.am
+++ b/xlators/performance/stat-prefetch/src/Makefile.am
@@ -1,11 +1,14 @@
-xlator_PROGRAMS = stat-prefetch.so
+xlator_LTLIBRARIES = stat-prefetch.la
 xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
 
-stat_prefetch_so_SOURCES = stat-prefetch.c
+stat_prefetch_la_LDFLAGS = -module -avoidversion
+stat_prefetch_la_SOURCES = stat-prefetch.c
 noinst_HEADERS = stat-prefetch.h
 
-AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall \
-	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles
+stat_prefetch_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS)\
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
 
 CLEANFILES = 
 
diff --git a/xlators/performance/stat-prefetch/src/stat-prefetch.c b/xlators/performance/stat-prefetch/src/stat-prefetch.c
index c6bf1e684cf..6a10ac4c42c 100644
--- a/xlators/performance/stat-prefetch/src/stat-prefetch.c
+++ b/xlators/performance/stat-prefetch/src/stat-prefetch.c
@@ -1,508 +1,53 @@
 /*
-   Copyright (c) 2006-2009 Z RESEARCH, Inc. <http://www.zresearch.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/>.
+  Copyright (c) 2009-2010 Z RESEARCH, Inc. <http://www.zresearch.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 "stat-prefetch.h"
-#include "dict.h"
-#include "xlator.h"
-#include <sys/time.h>
-
-struct sp_cache {
-  struct sp_cache *next;
-  struct sp_cache *prev;
-  pid_t pid;
-  long long tv_time;
-  char *dirname;
-  dir_entry_t entries;
-  int32_t count;
-  pthread_mutex_t lock;
-};
-
-static void
-stat_prefetch_cache_flush (struct sp_cache *cache, int32_t force)
-{
-  struct sp_cache *trav;
-  struct timeval tv;
-  long long tv_time;
-
-  gettimeofday (&tv, NULL);
-  tv_time = (tv.tv_usec + (tv.tv_sec * 1000000));
-
-  pthread_mutex_lock (&cache->lock);
-
-  trav = cache->next;
-  while (trav != cache) {
-    struct sp_cache *next = trav->next;
-    {
-      if (tv_time > trav->tv_time || force) {
-	gf_log ("stat-prefetch",
-		GF_LOG_DEBUG,
-		"flush on: %s",
-		trav->dirname);
-	dir_entry_t *entries;
-
-	trav->prev->next = trav->next;
-	trav->next->prev = trav->prev;
-
-	entries = trav->entries.next;
-
-	while (entries) {
-	  dir_entry_t *nextentry = entries->next;
-	  {
-	    free (entries->name);
-	    free (entries);
-	  }
-	  entries = nextentry;
-	}
-	free (trav->dirname);
-	free (trav);
-      }
-    }
-    trav = next;
-  }
-
-  pthread_mutex_unlock (&cache->lock);
-}
-
-static int32_t
-stat_prefetch_cache_fill (struct sp_cache *cache,
-			  pid_t pid,
-			  char *dirname,
-			  dir_entry_t *entries)
-{
-  struct sp_cache *trav;
-  struct timeval tv;
-
-  pthread_mutex_unlock (&cache->lock);
-  trav = cache->next;
-  while (trav != cache) {
-    //    if (trav->pid == pid && !strcmp (trav->dirname, dirname)) {
-    if (!strcmp (trav->dirname, dirname)) {
-      break;
-    }
-    trav = trav->next;
-  }
-
-  if (trav == cache) {
-    trav = CALLOC (1, sizeof (*trav));
-    ERR_ABORT (trav);
-    trav->pid = pid;
-    trav->dirname = dirname;
-
-    trav->prev = cache->prev;
-    trav->next = cache;
-    trav->next->prev = trav;
-    trav->prev->next = trav;
-  } else {
-    free (dirname);
-  }
-
-  while (trav->entries.next) {
-    dir_entry_t *tmp = trav->entries.next;
-
-    trav->entries.next = trav->entries.next->next;
-    free (tmp->name);
-    free (tmp);
-  }
-  trav->entries.next = entries->next;
-  entries->next = NULL;
-
-  gettimeofday (&tv, NULL);
-  trav->tv_time = (tv.tv_usec + (tv.tv_sec * 1000000)) + cache->tv_time;
-
-  pthread_mutex_unlock (&cache->lock);
-  return 0;
-}
-
-static int32_t
-stat_prefetch_cache_lookup (struct sp_cache *cache,
-			    pid_t pid,
-			    const char *path,
-			    struct stat *buf)
-{
-  struct sp_cache *trav;
-  char *dirname = strdup (path);
-  char *filename = strrchr (dirname, '/');
-  dir_entry_t *entries;
-  dir_entry_t *prev = NULL;
-
-  *filename = '\0';
-  filename ++;
-
-  pthread_mutex_lock (&cache->lock);
-  trav = cache->next;
-  while (trav != cache) {
-    //    if ((trav->pid == pid) && !strcmp (dirname, trav->dirname))
-    if (!strcmp (dirname, trav->dirname))
-      break;
-    trav = trav->next;
-  }
-  if (trav == cache) {
-    free (dirname);
-    pthread_mutex_unlock (&cache->lock);
-    return -1;
-  }
-
-  entries = trav->entries.next;
-  prev = &trav->entries;
-  while (entries) {
-    if (!strcmp (entries->name, filename))
-      break;
-    prev = entries;
-    entries = entries->next;
-  }
-  if (!entries) {
-    free (dirname);
-    pthread_mutex_unlock (&cache->lock);
-    return -1;
-  }
-
-  *buf = entries->buf;
-  prev->next = entries->next;
-  free (entries->name);
-  free (entries);
-  free (dirname);
-
-  pthread_mutex_unlock (&cache->lock);
-
-  return 0;
-}
-
-			    
-int32_t
-stat_prefetch_readdir_cbk (call_frame_t *frame,
-			   void *cookie,
-			   xlator_t *this,
-			   int32_t op_ret,
-			   int32_t op_errno,
-			   dir_entry_t *entries,
-			   int32_t count)
-{
-  char *path = frame->local;
-  pid_t pid = frame->root->pid;
-  frame->local = NULL;
-
-  STACK_UNWIND (frame, op_ret, op_errno, entries, count);
-
-  if (op_ret == 0)
-    stat_prefetch_cache_fill (this->private,
-			      pid,
-			      path,
-			      entries);
-  else
-    free (path);
-
-  return 0;
-}
-
-int32_t
-stat_prefetch_readdir (call_frame_t *frame,
-		       xlator_t *this,
-		       const char *path)
-{
-  stat_prefetch_cache_flush (this->private, 0);
-
-  frame->local = strdup (path);
-  STACK_WIND (frame,
-	      stat_prefetch_readdir_cbk,
-	      FIRST_CHILD(this),
-	      FIRST_CHILD(this)->fops->readdir,
-	      path);
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_getattr_cbk (call_frame_t *frame,
-			   void *cookie,
-			   xlator_t *this,
-			   int32_t op_ret,
-			   int32_t op_errno,
-			   struct stat *buf)
-{
-  STACK_UNWIND (frame, op_ret, op_errno, buf);
-  return 0;
-}
-
-int32_t
-stat_prefetch_getattr (call_frame_t *frame,
-		       struct xlator *this,
-		       const char *path)
-{
-  struct stat buf;
-  pid_t pid = frame->root->pid;
-  stat_prefetch_cache_flush (this->private, 0);
-
-  if (stat_prefetch_cache_lookup (this->private,
-				  pid,
-				  path,
-				  &buf) == 0) {
-    STACK_UNWIND (frame, 0, 0, &buf);
-    return 0;
-  }
-
-  STACK_WIND (frame,
-	      stat_prefetch_getattr_cbk,
-	      FIRST_CHILD(this),
-	      FIRST_CHILD(this)->fops->getattr,
-	      path);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_unlink_cbk (call_frame_t *frame,
-                          void *cookie,
-                          xlator_t *this,
-                          int32_t op_ret,
-                          int32_t op_errno)
-{
-  STACK_UNWIND (frame, op_ret, op_errno);
-  return 0;
-}
-
-int32_t
-stat_prefetch_unlink (call_frame_t *frame,
-                      struct xlator *this,
-                      const char *path)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_unlink_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->unlink,
-              path);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_chmod_cbk (call_frame_t *frame,
-			 void *cookie,
-			 xlator_t *this,
-			 int32_t op_ret,
-			 int32_t op_errno,
-			 struct stat *buf)
-{
-  STACK_UNWIND (frame, op_ret, op_errno, buf);
-  return 0;
-}
-
-int32_t
-stat_prefetch_chmod (call_frame_t *frame,
-		     struct xlator *this,
-		     const char *path,
-		     mode_t mode)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_chmod_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->chmod,
-              path,
-	      mode);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_chown_cbk (call_frame_t *frame,
-			 void *cookie,
-			 xlator_t *this,
-			 int32_t op_ret,
-			 int32_t op_errno,
-			 struct stat *buf)
-{
-  STACK_UNWIND (frame, op_ret, op_errno, buf);
-  return 0;
-}
-
-int32_t
-stat_prefetch_chown (call_frame_t *frame,
-		     struct xlator *this,
-		     const char *path,
-		     uid_t uid,
-		     gid_t gid)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_chown_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->chown,
-              path,
-	      uid,
-	      gid);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_utimes_cbk (call_frame_t *frame,
-                          void *cookie,
-                          xlator_t *this,
-                          int32_t op_ret,
-                          int32_t op_errno,
-			  struct stat *buf)
-{
-  STACK_UNWIND (frame, op_ret, op_errno, buf);
-  return 0;
-}
-
-int32_t
-stat_prefetch_utimes (call_frame_t *frame,
-		      struct xlator *this,
-		      const char *path,
-		      struct timespec *tvp)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_utimes_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->utimes,
-              path,
-	      tvp);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_truncate_cbk (call_frame_t *frame,
-			    void *cookie,
-			    xlator_t *this,
-			    int32_t op_ret,
-			    int32_t op_errno,
-			    struct stat *buf)
-{
-  STACK_UNWIND (frame, op_ret, op_errno, buf);
-  return 0;
-}
-
-int32_t
-stat_prefetch_truncate (call_frame_t *frame,
-			struct xlator *this,
-			const char *path,
-			off_t offset)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_truncate_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->truncate,
-              path,
-	      offset);
-
-  return 0;
-}
-
-
-int32_t
-stat_prefetch_rename_cbk (call_frame_t *frame,
-                          void *cookie,
-                          xlator_t *this,
-                          int32_t op_ret,
-                          int32_t op_errno)
-{
-  STACK_UNWIND (frame, op_ret, op_errno);
-  return 0;
-}
-
-int32_t
-stat_prefetch_rename (call_frame_t *frame,
-                      struct xlator *this,
-                      const char *oldpath,
-		      const char *newpath)
-{
-  stat_prefetch_cache_flush (this->private, 1);
-
-  STACK_WIND (frame,
-              stat_prefetch_rename_cbk,
-              FIRST_CHILD(this),
-              FIRST_CHILD(this)->fops->rename,
-              oldpath,
-	      newpath);
-
-  return 0;
-}
 
 int32_t 
-init (struct xlator *this)
+init (xlator_t *this)
 {
-  struct sp_cache *cache;
-  dict_t *options = this->options;
+        int32_t ret = -1;
+        if (!this->children || this->children->next) {
+                gf_log ("stat-prefetch",
+                        GF_LOG_ERROR,
+                        "FATAL: translator %s does not have exactly one child "
+                        "node", this->name);
+                goto out;
+        }
 
-  if (!this->children || this->children->next) {
-    gf_log ("stat-prefetch",
-	    GF_LOG_ERROR,
-	    "FATAL: translator %s does not have exactly one child node",
-	    this->name);
-    return -1;
-  }
-
-  cache = (void *) CALLOC (1, sizeof (*cache));
-  ERR_ABORT (cache);
-  cache->next = cache->prev = cache;
-
-  cache->tv_time = 1 * 1000000;
-
-  if (dict_get (options, "cache-seconds")) {
-    cache->tv_time = (data_to_int64 (dict_get (options, "cache-seconds")) *
-		      1000000);
-  }
-
-  pthread_mutex_init (&cache->lock, NULL);
-
-  this->private = cache;
-  return 0;
+        ret = 0;
+out:
+        return ret;
 }
 
 void
-fini (struct xlator *this)
+fini (xlator_t *this)
 {
-  return;
+        return;
 }
 
 
 struct xlator_fops fops = {
-  .getattr     = stat_prefetch_getattr,
-  .readdir     = stat_prefetch_readdir,
-  .unlink      = stat_prefetch_unlink,
-  .chmod       = stat_prefetch_chmod,
-  .chown       = stat_prefetch_chown,
-  .rename      = stat_prefetch_rename,
-  .utimes      = stat_prefetch_utimes,
-  .truncate    = stat_prefetch_truncate,
 };
 
 struct xlator_mops mops = {
 };
+
+struct xlator_cbks cbks = {
+};
diff --git a/xlators/performance/stat-prefetch/src/stat-prefetch.h b/xlators/performance/stat-prefetch/src/stat-prefetch.h
index ef82952b0c7..bd8d9e7eb17 100644
--- a/xlators/performance/stat-prefetch/src/stat-prefetch.h
+++ b/xlators/performance/stat-prefetch/src/stat-prefetch.h
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2006-2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+   Copyright (c) 2009-2010 Z RESEARCH, Inc. <http://www.zresearch.com>
    This file is part of GlusterFS.
 
    GlusterFS is free software; you can redistribute it and/or modify
@@ -17,16 +17,16 @@
    <http://www.gnu.org/licenses/>.
 */
 
-#ifndef _STAT_PREFETCH_H_
-#define _STAT_PREFETCH_H_
+#ifndef _STAT_PREFETCH_H
+#define _STAT_PREFETCH_H
 
 #ifndef _CONFIG_H
 #define _CONFIG_H
 #include "config.h"
 #endif
 
-#include <stdio.h>
-#include <sys/time.h>
+#include "glusterfs.h"
+#include "dict.h"
 #include "xlator.h"
 
-#endif /* _STAT_PREFETCH_H_ */
+#endif  /* #ifndef _STAT_PREFETCH_H */