[PATCH 2/2] ocfs2: cluster aware flock()

Hook up ocfs2_flock(), using the new flock lock type in dlmglue.c. A new
mount option, "localflocks" is added so that users can revert to old
functionality as need be.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

Documentation/filesystems/ocfs2.txt

@@ -75,3 +75,4 @@ commit=nrsec	(*)	Ocfs2 can be told to sync all its data and metadata
 localalloc=8(*)		Allows custom localalloc size in MB. If the value is too
 			large, the fs will silently revert it to the default.
 			Localalloc is not enabled for local mounts.
+localflocks		This disables cluster aware flock.

fs/ocfs2/Makefile

@@ -19,6 +19,7 @@ ocfs2-objs := \
 	ioctl.o 		\
 	journal.o 		\
 	localalloc.o 		\
+	locks.o			\
 	mmap.o 			\
 	namei.o 		\
 	resize.o		\

fs/ocfs2/file.c

@@ -51,6 +51,7 @@
 #include "inode.h"
 #include "ioctl.h"
 #include "journal.h"
+#include "locks.h"
 #include "mmap.h"
 #include "suballoc.h"
 #include "super.h"
@@ -63,6 +64,35 @@ static int ocfs2_sync_inode(struct inode *inode)
 	return sync_mapping_buffers(inode->i_mapping);
 }
 
+static int ocfs2_init_file_private(struct inode *inode, struct file *file)
+{
+	struct ocfs2_file_private *fp;
+
+	fp = kzalloc(sizeof(struct ocfs2_file_private), GFP_KERNEL);
+	if (!fp)
+		return -ENOMEM;
+
+	fp->fp_file = file;
+	mutex_init(&fp->fp_mutex);
+	ocfs2_file_lock_res_init(&fp->fp_flock, fp);
+	file->private_data = fp;
+
+	return 0;
+}
+
+static void ocfs2_free_file_private(struct inode *inode, struct file *file)
+{
+	struct ocfs2_file_private *fp = file->private_data;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+	if (fp) {
+		ocfs2_simple_drop_lockres(osb, &fp->fp_flock);
+		ocfs2_lock_res_free(&fp->fp_flock);
+		kfree(fp);
+		file->private_data = NULL;
+	}
+}
+
 static int ocfs2_file_open(struct inode *inode, struct file *file)
 {
 	int status;
@@ -89,7 +119,18 @@ static int ocfs2_file_open(struct inode *inode, struct file *file)
 
 	oi->ip_open_count++;
 	spin_unlock(&oi->ip_lock);
-	status = 0;
+
+	status = ocfs2_init_file_private(inode, file);
+	if (status) {
+		/*
+		 * We want to set open count back if we're failing the
+		 * open.
+		 */
+		spin_lock(&oi->ip_lock);
+		oi->ip_open_count--;
+		spin_unlock(&oi->ip_lock);
+	}
+
 leave:
 	mlog_exit(status);
 	return status;
@@ -108,11 +149,24 @@ static int ocfs2_file_release(struct inode *inode, struct file *file)
 		oi->ip_flags &= ~OCFS2_INODE_OPEN_DIRECT;
 	spin_unlock(&oi->ip_lock);
 
+	ocfs2_free_file_private(inode, file);
+
 	mlog_exit(0);
 
 	return 0;
 }
 
+static int ocfs2_dir_open(struct inode *inode, struct file *file)
+{
+	return ocfs2_init_file_private(inode, file);
+}
+
+static int ocfs2_dir_release(struct inode *inode, struct file *file)
+{
+	ocfs2_free_file_private(inode, file);
+	return 0;
+}
+
 static int ocfs2_sync_file(struct file *file,
 			   struct dentry *dentry,
 			   int datasync)
@@ -2191,6 +2245,7 @@ const struct file_operations ocfs2_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl   = ocfs2_compat_ioctl,
 #endif
+	.flock		= ocfs2_flock,
 	.splice_read	= ocfs2_file_splice_read,
 	.splice_write	= ocfs2_file_splice_write,
 };
@@ -2199,8 +2254,11 @@ const struct file_operations ocfs2_dops = {
 	.read		= generic_read_dir,
 	.readdir	= ocfs2_readdir,
 	.fsync		= ocfs2_sync_file,
+	.release	= ocfs2_dir_release,
+	.open		= ocfs2_dir_open,
 	.ioctl		= ocfs2_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl   = ocfs2_compat_ioctl,
 #endif
+	.flock		= ocfs2_flock,
 };

fs/ocfs2/locks.c

+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * locks.c
+ *
+ * Userspace file locking support
+ *
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ *
+ * This program 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 2 of the License, or (at your option) any later version.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/fs.h>
+
+#define MLOG_MASK_PREFIX ML_INODE
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+
+#include "dlmglue.h"
+#include "file.h"
+#include "locks.h"
+
+static int ocfs2_do_flock(struct file *file, struct inode *inode,
+			  int cmd, struct file_lock *fl)
+{
+	int ret = 0, level = 0, trylock = 0;
+	struct ocfs2_file_private *fp = file->private_data;
+	struct ocfs2_lock_res *lockres = &fp->fp_flock;
+
+	if (fl->fl_type == F_WRLCK)
+		level = 1;
+	if (!IS_SETLKW(cmd))
+		trylock = 1;
+
+	mutex_lock(&fp->fp_mutex);
+
+	if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
+	    lockres->l_level > LKM_NLMODE) {
+		int old_level = 0;
+
+		if (lockres->l_level == LKM_EXMODE)
+			old_level = 1;
+
+		if (level == old_level)
+			goto out;
+
+		/*
+		 * Converting an existing lock is not guaranteed to be
+		 * atomic, so we can get away with simply unlocking
+		 * here and allowing the lock code to try at the new
+		 * level.
+		 */
+
+		flock_lock_file_wait(file,
+				     &(struct file_lock){.fl_type = F_UNLCK});
+
+		ocfs2_file_unlock(file);
+	}
+
+	ret = ocfs2_file_lock(file, level, trylock);
+	if (ret) {
+		if (ret == -EAGAIN && trylock)
+			ret = -EWOULDBLOCK;
+		else
+			mlog_errno(ret);
+		goto out;
+	}
+
+	ret = flock_lock_file_wait(file, fl);
+
+out:
+	mutex_unlock(&fp->fp_mutex);
+
+	return ret;
+}
+
+static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
+{
+	int ret;
+	struct ocfs2_file_private *fp = file->private_data;
+
+	mutex_lock(&fp->fp_mutex);
+	ocfs2_file_unlock(file);
+	ret = flock_lock_file_wait(file, fl);
+	mutex_unlock(&fp->fp_mutex);
+
+	return ret;
+}
+
+/*
+ * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
+ */
+int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+	if (!(fl->fl_flags & FL_FLOCK))
+		return -ENOLCK;
+	if (__mandatory_lock(inode))
+		return -ENOLCK;
+
+	if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
+	    ocfs2_mount_local(osb))
+		return flock_lock_file_wait(file, fl);
+
+	if (fl->fl_type == F_UNLCK)
+		return ocfs2_do_funlock(file, cmd, fl);
+	else
+		return ocfs2_do_flock(file, inode, cmd, fl);
+}

fs/ocfs2/locks.h

+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * locks.h
+ *
+ * Function prototypes for Userspace file locking support
+ *
+ * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
+ *
+ * This program 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 2 of the License, or (at your option) any later version.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef OCFS2_LOCKS_H
+#define OCFS2_LOCKS_H
+
+int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl);
+
+#endif /* OCFS2_LOCKS_H */

fs/ocfs2/ocfs2.h

@@ -171,6 +171,7 @@ enum ocfs2_mount_options
 	OCFS2_MOUNT_NOINTR  = 1 << 2,   /* Don't catch signals */
 	OCFS2_MOUNT_ERRORS_PANIC = 1 << 3, /* Panic on errors */
 	OCFS2_MOUNT_DATA_WRITEBACK = 1 << 4, /* No data ordering */
+	OCFS2_MOUNT_LOCALFLOCKS = 1 << 5, /* No cluster aware user file locks */
 };
 
 #define OCFS2_OSB_SOFT_RO	0x0001

fs/ocfs2/super.c

@@ -153,6 +153,7 @@ enum {
 	Opt_slot,
 	Opt_commit,
 	Opt_localalloc,
+	Opt_localflocks,
 	Opt_err,
 };
 
@@ -170,6 +171,7 @@ static match_table_t tokens = {
 	{Opt_slot, "preferred_slot=%u"},
 	{Opt_commit, "commit=%u"},
 	{Opt_localalloc, "localalloc=%d"},
+	{Opt_localflocks, "localflocks"},
 	{Opt_err, NULL}
 };
 
@@ -848,6 +850,20 @@ static int ocfs2_parse_options(struct super_block *sb,
 			if (option >= 0 && (option <= ocfs2_local_alloc_size(sb) * 8))
 				mopt->localalloc_opt = option;
 			break;
+		case Opt_localflocks:
+			/*
+			 * Changing this during remount could race
+			 * flock() requests, or "unbalance" existing
+			 * ones (e.g., a lock is taken in one mode but
+			 * dropped in the other). If users care enough
+			 * to flip locking modes during remount, we
+			 * could add a "local" flag to individual
+			 * flock structures for proper tracking of
+			 * state.
+			 */
+			if (!is_remount)
+				mopt->mount_opt |= OCFS2_MOUNT_LOCALFLOCKS;
+			break;
 		default:
 			mlog(ML_ERROR,
 			     "Unrecognized mount option \"%s\" "
@@ -903,6 +919,9 @@ static int ocfs2_show_options(struct seq_file *s, struct vfsmount *mnt)
 	if (osb->local_alloc_size != OCFS2_DEFAULT_LOCAL_ALLOC_SIZE)
 		seq_printf(s, ",localalloc=%d", osb->local_alloc_size);
 
+	if (opts & OCFS2_MOUNT_LOCALFLOCKS)
+		seq_printf(s, ",localflocks,");
+
 	return 0;
 }