/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * userdlm.c
   *
   * Code which implements the kernel side of a minimal userspace
   * interface to our DLM.
   *
   * Many of the functions here are pared down versions of dlmglue.c
   * functions.
   *
   * Copyright (C) 2003, 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.
   */
  
  #include <linux/signal.h>
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/types.h>
  #include <linux/crc32.h>
  
  #include "ocfs2_lockingver.h"
  #include "stackglue.h"
  #include "userdlm.h"
  
  #define MLOG_MASK_PREFIX ML_DLMFS
  #include "cluster/masklog.h"
  
  
  static inline struct user_lock_res *user_lksb_to_lock_res(struct ocfs2_dlm_lksb *lksb)
  {
  	return container_of(lksb, struct user_lock_res, l_lksb);
  }
  
  static inline int user_check_wait_flag(struct user_lock_res *lockres,
  				       int flag)
  {
  	int ret;
  
  	spin_lock(&lockres->l_lock);
  	ret = lockres->l_flags & flag;
  	spin_unlock(&lockres->l_lock);
  
  	return ret;
  }
  
  static inline void user_wait_on_busy_lock(struct user_lock_res *lockres)
  
  {
  	wait_event(lockres->l_event,
  		   !user_check_wait_flag(lockres, USER_LOCK_BUSY));
  }
  
  static inline void user_wait_on_blocked_lock(struct user_lock_res *lockres)
  
  {
  	wait_event(lockres->l_event,
  		   !user_check_wait_flag(lockres, USER_LOCK_BLOCKED));
  }
  
  /* I heart container_of... */
  static inline struct ocfs2_cluster_connection *
  cluster_connection_from_user_lockres(struct user_lock_res *lockres)
  {
  	struct dlmfs_inode_private *ip;
  
  	ip = container_of(lockres,
  			  struct dlmfs_inode_private,
  			  ip_lockres);
  	return ip->ip_conn;
  }
  
  static struct inode *
  user_dlm_inode_from_user_lockres(struct user_lock_res *lockres)
  {
  	struct dlmfs_inode_private *ip;
  
  	ip = container_of(lockres,
  			  struct dlmfs_inode_private,
  			  ip_lockres);
  	return &ip->ip_vfs_inode;
  }
  
  static inline void user_recover_from_dlm_error(struct user_lock_res *lockres)
  {
  	spin_lock(&lockres->l_lock);
  	lockres->l_flags &= ~USER_LOCK_BUSY;
  	spin_unlock(&lockres->l_lock);
  }
  
  #define user_log_dlm_error(_func, _stat, _lockres) do {			\
  	mlog(ML_ERROR, "Dlm error %d while calling %s on "		\
  		"resource %.*s
  ", _stat, _func,			\
  		_lockres->l_namelen, _lockres->l_name); 		\
  } while (0)
  
  /* WARNING: This function lives in a world where the only three lock
   * levels are EX, PR, and NL. It *will* have to be adjusted when more
   * lock types are added. */
  static inline int user_highest_compat_lock_level(int level)
  {
  	int new_level = DLM_LOCK_EX;
  
  	if (level == DLM_LOCK_EX)
  		new_level = DLM_LOCK_NL;
  	else if (level == DLM_LOCK_PR)
  		new_level = DLM_LOCK_PR;
  	return new_level;
  }
  
  static void user_ast(struct ocfs2_dlm_lksb *lksb)
  {
  	struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
  	int status;
  
  	mlog(ML_BASTS, "AST fired for lockres %.*s, level %d => %d
  ",
  	     lockres->l_namelen, lockres->l_name, lockres->l_level,
  	     lockres->l_requested);
  
  	spin_lock(&lockres->l_lock);
  
  	status = ocfs2_dlm_lock_status(&lockres->l_lksb);
  	if (status) {
  		mlog(ML_ERROR, "lksb status value of %u on lockres %.*s
  ",
  		     status, lockres->l_namelen, lockres->l_name);
  		spin_unlock(&lockres->l_lock);
  		return;
  	}
  
  	mlog_bug_on_msg(lockres->l_requested == DLM_LOCK_IV,
  			"Lockres %.*s, requested ivmode. flags 0x%x
  ",
  			lockres->l_namelen, lockres->l_name, lockres->l_flags);
  
  	/* we're downconverting. */
  	if (lockres->l_requested < lockres->l_level) {
  		if (lockres->l_requested <=
  		    user_highest_compat_lock_level(lockres->l_blocking)) {
  			lockres->l_blocking = DLM_LOCK_NL;
  			lockres->l_flags &= ~USER_LOCK_BLOCKED;
  		}
  	}
  
  	lockres->l_level = lockres->l_requested;
  	lockres->l_requested = DLM_LOCK_IV;
  	lockres->l_flags |= USER_LOCK_ATTACHED;
  	lockres->l_flags &= ~USER_LOCK_BUSY;
  
  	spin_unlock(&lockres->l_lock);
  
  	wake_up(&lockres->l_event);
  }
  
  static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
  {
  	struct inode *inode;
  	inode = user_dlm_inode_from_user_lockres(lockres);
  	if (!igrab(inode))
  		BUG();
  }
  
  static void user_dlm_unblock_lock(struct work_struct *work);
  
  static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
  {
  	if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
  		user_dlm_grab_inode_ref(lockres);
  
  		INIT_WORK(&lockres->l_work, user_dlm_unblock_lock);
  
  		queue_work(user_dlm_worker, &lockres->l_work);
  		lockres->l_flags |= USER_LOCK_QUEUED;
  	}
  }
  
  static void __user_dlm_cond_queue_lockres(struct user_lock_res *lockres)
  {
  	int queue = 0;
  
  	if (!(lockres->l_flags & USER_LOCK_BLOCKED))
  		return;
  
  	switch (lockres->l_blocking) {
  	case DLM_LOCK_EX:
  		if (!lockres->l_ex_holders && !lockres->l_ro_holders)
  			queue = 1;
  		break;
  	case DLM_LOCK_PR:
  		if (!lockres->l_ex_holders)
  			queue = 1;
  		break;
  	default:
  		BUG();
  	}
  
  	if (queue)
  		__user_dlm_queue_lockres(lockres);
  }
  
  static void user_bast(struct ocfs2_dlm_lksb *lksb, int level)
  {
  	struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
  
  	mlog(ML_BASTS, "BAST fired for lockres %.*s, blocking %d, level %d
  ",
  	     lockres->l_namelen, lockres->l_name, level, lockres->l_level);
  
  	spin_lock(&lockres->l_lock);
  	lockres->l_flags |= USER_LOCK_BLOCKED;
  	if (level > lockres->l_blocking)
  		lockres->l_blocking = level;
  
  	__user_dlm_queue_lockres(lockres);
  	spin_unlock(&lockres->l_lock);
  
  	wake_up(&lockres->l_event);
  }
  
  static void user_unlock_ast(struct ocfs2_dlm_lksb *lksb, int status)
  {
  	struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
  
  	mlog(ML_BASTS, "UNLOCK AST fired for lockres %.*s, flags 0x%x
  ",
  	     lockres->l_namelen, lockres->l_name, lockres->l_flags);
  
  	if (status)
  		mlog(ML_ERROR, "dlm returns status %d
  ", status);
  
  	spin_lock(&lockres->l_lock);
  	/* The teardown flag gets set early during the unlock process,
  	 * so test the cancel flag to make sure that this ast isn't
  	 * for a concurrent cancel. */
  	if (lockres->l_flags & USER_LOCK_IN_TEARDOWN
  	    && !(lockres->l_flags & USER_LOCK_IN_CANCEL)) {
  		lockres->l_level = DLM_LOCK_IV;
  	} else if (status == DLM_CANCELGRANT) {
  		/* We tried to cancel a convert request, but it was
  		 * already granted. Don't clear the busy flag - the
  		 * ast should've done this already. */
  		BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
  		lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
  		goto out_noclear;
  	} else {
  		BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
  		/* Cancel succeeded, we want to re-queue */
  		lockres->l_requested = DLM_LOCK_IV; /* cancel an
  						    * upconvert
  						    * request. */
  		lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
  		/* we want the unblock thread to look at it again
  		 * now. */
  		if (lockres->l_flags & USER_LOCK_BLOCKED)
  			__user_dlm_queue_lockres(lockres);
  	}
  
  	lockres->l_flags &= ~USER_LOCK_BUSY;
  out_noclear:
  	spin_unlock(&lockres->l_lock);
  
  	wake_up(&lockres->l_event);
  }
  
  /*
   * This is the userdlmfs locking protocol version.
   *
   * See fs/ocfs2/dlmglue.c for more details on locking versions.
   */
  static struct ocfs2_locking_protocol user_dlm_lproto = {
  	.lp_max_version = {
  		.pv_major = OCFS2_LOCKING_PROTOCOL_MAJOR,
  		.pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
  	},
  	.lp_lock_ast		= user_ast,
  	.lp_blocking_ast	= user_bast,
  	.lp_unlock_ast		= user_unlock_ast,
  };
  
  static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
  {
  	struct inode *inode;
  	inode = user_dlm_inode_from_user_lockres(lockres);
  	iput(inode);
  }
  
  static void user_dlm_unblock_lock(struct work_struct *work)
  {
  	int new_level, status;
  	struct user_lock_res *lockres =
  		container_of(work, struct user_lock_res, l_work);
  	struct ocfs2_cluster_connection *conn =
  		cluster_connection_from_user_lockres(lockres);
  
  	mlog(0, "lockres %.*s
  ", lockres->l_namelen, lockres->l_name);
  
  	spin_lock(&lockres->l_lock);
  
  	mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
  			"Lockres %.*s, flags 0x%x
  ",
  			lockres->l_namelen, lockres->l_name, lockres->l_flags);
  
  	/* notice that we don't clear USER_LOCK_BLOCKED here. If it's
  	 * set, we want user_ast clear it. */
  	lockres->l_flags &= ~USER_LOCK_QUEUED;
  
  	/* It's valid to get here and no longer be blocked - if we get
  	 * several basts in a row, we might be queued by the first
  	 * one, the unblock thread might run and clear the queued
  	 * flag, and finally we might get another bast which re-queues
  	 * us before our ast for the downconvert is called. */
  	if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
  		mlog(ML_BASTS, "lockres %.*s USER_LOCK_BLOCKED
  ",
  		     lockres->l_namelen, lockres->l_name);
  		spin_unlock(&lockres->l_lock);
  		goto drop_ref;
  	}
  
  	if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
  		mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_TEARDOWN
  ",
  		     lockres->l_namelen, lockres->l_name);
  		spin_unlock(&lockres->l_lock);
  		goto drop_ref;
  	}
  
  	if (lockres->l_flags & USER_LOCK_BUSY) {
  		if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
  			mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_CANCEL
  ",
  			     lockres->l_namelen, lockres->l_name);
  			spin_unlock(&lockres->l_lock);
  			goto drop_ref;
  		}
  
  		lockres->l_flags |= USER_LOCK_IN_CANCEL;
  		spin_unlock(&lockres->l_lock);
  
  		status = ocfs2_dlm_unlock(conn, &lockres->l_lksb,
  					  DLM_LKF_CANCEL);
  		if (status)
  			user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
  		goto drop_ref;
  	}
  
  	/* If there are still incompat holders, we can exit safely
  	 * without worrying about re-queueing this lock as that will
  	 * happen on the last call to user_cluster_unlock. */
  	if ((lockres->l_blocking == DLM_LOCK_EX)
  	    && (lockres->l_ex_holders || lockres->l_ro_holders)) {
  		spin_unlock(&lockres->l_lock);
  		mlog(ML_BASTS, "lockres %.*s, EX/PR Holders %u,%u
  ",
  		     lockres->l_namelen, lockres->l_name,
  		     lockres->l_ex_holders, lockres->l_ro_holders);
  		goto drop_ref;
  	}
  
  	if ((lockres->l_blocking == DLM_LOCK_PR)
  	    && lockres->l_ex_holders) {
  		spin_unlock(&lockres->l_lock);
  		mlog(ML_BASTS, "lockres %.*s, EX Holders %u
  ",
  		     lockres->l_namelen, lockres->l_name,
  		     lockres->l_ex_holders);
  		goto drop_ref;
  	}
  
  	/* yay, we can downconvert now. */
  	new_level = user_highest_compat_lock_level(lockres->l_blocking);
  	lockres->l_requested = new_level;
  	lockres->l_flags |= USER_LOCK_BUSY;
  	mlog(ML_BASTS, "lockres %.*s, downconvert %d => %d
  ",
  	     lockres->l_namelen, lockres->l_name, lockres->l_level, new_level);
  	spin_unlock(&lockres->l_lock);
  
  	/* need lock downconvert request now... */
  	status = ocfs2_dlm_lock(conn, new_level, &lockres->l_lksb,
  				DLM_LKF_CONVERT|DLM_LKF_VALBLK,
  				lockres->l_name,
  				lockres->l_namelen);
  	if (status) {
  		user_log_dlm_error("ocfs2_dlm_lock", status, lockres);
  		user_recover_from_dlm_error(lockres);
  	}
  
  drop_ref:
  	user_dlm_drop_inode_ref(lockres);
  }
  
  static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
  					int level)
  {
  	switch(level) {
  	case DLM_LOCK_EX:
  		lockres->l_ex_holders++;
  		break;
  	case DLM_LOCK_PR:
  		lockres->l_ro_holders++;
  		break;
  	default:
  		BUG();
  	}
  }
  
  /* predict what lock level we'll be dropping down to on behalf
   * of another node, and return true if the currently wanted
   * level will be compatible with it. */
  static inline int
  user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
  				  int wanted)
  {
  	BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));
  
  	return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
  }
  
  int user_dlm_cluster_lock(struct user_lock_res *lockres,
  			  int level,
  			  int lkm_flags)
  {
  	int status, local_flags;
  	struct ocfs2_cluster_connection *conn =
  		cluster_connection_from_user_lockres(lockres);
  
  	if (level != DLM_LOCK_EX &&
  	    level != DLM_LOCK_PR) {
  		mlog(ML_ERROR, "lockres %.*s: invalid request!
  ",
  		     lockres->l_namelen, lockres->l_name);
  		status = -EINVAL;
  		goto bail;
  	}
  
  	mlog(ML_BASTS, "lockres %.*s, level %d, flags = 0x%x
  ",
  	     lockres->l_namelen, lockres->l_name, level, lkm_flags);
  
  again:
  	if (signal_pending(current)) {
  		status = -ERESTARTSYS;
  		goto bail;
  	}
  
  	spin_lock(&lockres->l_lock);
  
  	/* We only compare against the currently granted level
  	 * here. If the lock is blocked waiting on a downconvert,
  	 * we'll get caught below. */
  	if ((lockres->l_flags & USER_LOCK_BUSY) &&
  	    (level > lockres->l_level)) {
  		/* is someone sitting in dlm_lock? If so, wait on
  		 * them. */
  		spin_unlock(&lockres->l_lock);
  
  		user_wait_on_busy_lock(lockres);
  		goto again;
  	}
  
  	if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
  	    (!user_may_continue_on_blocked_lock(lockres, level))) {
  		/* is the lock is currently blocked on behalf of
  		 * another node */
  		spin_unlock(&lockres->l_lock);
  
  		user_wait_on_blocked_lock(lockres);
  		goto again;
  	}
  
  	if (level > lockres->l_level) {
  		local_flags = lkm_flags | DLM_LKF_VALBLK;
  		if (lockres->l_level != DLM_LOCK_IV)
  			local_flags |= DLM_LKF_CONVERT;
  
  		lockres->l_requested = level;
  		lockres->l_flags |= USER_LOCK_BUSY;
  		spin_unlock(&lockres->l_lock);
  
  		BUG_ON(level == DLM_LOCK_IV);
  		BUG_ON(level == DLM_LOCK_NL);
  
  		/* call dlm_lock to upgrade lock now */
  		status = ocfs2_dlm_lock(conn, level, &lockres->l_lksb,
  					local_flags, lockres->l_name,
  					lockres->l_namelen);
  		if (status) {
  			if ((lkm_flags & DLM_LKF_NOQUEUE) &&
  			    (status != -EAGAIN))
  				user_log_dlm_error("ocfs2_dlm_lock",
  						   status, lockres);
  			user_recover_from_dlm_error(lockres);
  			goto bail;
  		}
  
  		user_wait_on_busy_lock(lockres);
  		goto again;
  	}
  
  	user_dlm_inc_holders(lockres, level);
  	spin_unlock(&lockres->l_lock);
  
  	status = 0;
  bail:
  	return status;
  }
  
  static inline void user_dlm_dec_holders(struct user_lock_res *lockres,
  					int level)
  {
  	switch(level) {
  	case DLM_LOCK_EX:
  		BUG_ON(!lockres->l_ex_holders);
  		lockres->l_ex_holders--;
  		break;
  	case DLM_LOCK_PR:
  		BUG_ON(!lockres->l_ro_holders);
  		lockres->l_ro_holders--;
  		break;
  	default:
  		BUG();
  	}
  }
  
  void user_dlm_cluster_unlock(struct user_lock_res *lockres,
  			     int level)
  {
  	if (level != DLM_LOCK_EX &&
  	    level != DLM_LOCK_PR) {
  		mlog(ML_ERROR, "lockres %.*s: invalid request!
  ",
  		     lockres->l_namelen, lockres->l_name);
  		return;
  	}
  
  	spin_lock(&lockres->l_lock);
  	user_dlm_dec_holders(lockres, level);
  	__user_dlm_cond_queue_lockres(lockres);
  	spin_unlock(&lockres->l_lock);
  }
  
  void user_dlm_write_lvb(struct inode *inode,
  			const char *val,
  			unsigned int len)
  {
  	struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
  	char *lvb;
  
  	BUG_ON(len > DLM_LVB_LEN);
  
  	spin_lock(&lockres->l_lock);
  
  	BUG_ON(lockres->l_level < DLM_LOCK_EX);
  	lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
  	memcpy(lvb, val, len);
  
  	spin_unlock(&lockres->l_lock);
  }
  
  ssize_t user_dlm_read_lvb(struct inode *inode,
  			  char *val,
  			  unsigned int len)
  {
  	struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
  	char *lvb;
  	ssize_t ret = len;
  
  	BUG_ON(len > DLM_LVB_LEN);
  
  	spin_lock(&lockres->l_lock);
  
  	BUG_ON(lockres->l_level < DLM_LOCK_PR);
  	if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)) {
  		lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
  		memcpy(val, lvb, len);
  	} else
  		ret = 0;
  
  	spin_unlock(&lockres->l_lock);
  	return ret;
  }
  
  void user_dlm_lock_res_init(struct user_lock_res *lockres,
  			    struct dentry *dentry)
  {
  	memset(lockres, 0, sizeof(*lockres));
  
  	spin_lock_init(&lockres->l_lock);
  	init_waitqueue_head(&lockres->l_event);
  	lockres->l_level = DLM_LOCK_IV;
  	lockres->l_requested = DLM_LOCK_IV;
  	lockres->l_blocking = DLM_LOCK_IV;
  
  	/* should have been checked before getting here. */
  	BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);
  
  	memcpy(lockres->l_name,
  	       dentry->d_name.name,
  	       dentry->d_name.len);
  	lockres->l_namelen = dentry->d_name.len;
  }
  
  int user_dlm_destroy_lock(struct user_lock_res *lockres)
  {
  	int status = -EBUSY;
  	struct ocfs2_cluster_connection *conn =
  		cluster_connection_from_user_lockres(lockres);
  
  	mlog(ML_BASTS, "lockres %.*s
  ", lockres->l_namelen, lockres->l_name);
  
  	spin_lock(&lockres->l_lock);
  	if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
  		spin_unlock(&lockres->l_lock);
  		return 0;
  	}
  
  	lockres->l_flags |= USER_LOCK_IN_TEARDOWN;
  
  	while (lockres->l_flags & USER_LOCK_BUSY) {
  		spin_unlock(&lockres->l_lock);
  
  		user_wait_on_busy_lock(lockres);
  
  		spin_lock(&lockres->l_lock);
  	}
  
  	if (lockres->l_ro_holders || lockres->l_ex_holders) {
  		spin_unlock(&lockres->l_lock);
  		goto bail;
  	}
  
  	status = 0;
  	if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
  		spin_unlock(&lockres->l_lock);
  		goto bail;
  	}
  
  	lockres->l_flags &= ~USER_LOCK_ATTACHED;
  	lockres->l_flags |= USER_LOCK_BUSY;
  	spin_unlock(&lockres->l_lock);
  
  	status = ocfs2_dlm_unlock(conn, &lockres->l_lksb, DLM_LKF_VALBLK);
  	if (status) {
  		user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
  		goto bail;
  	}
  
  	user_wait_on_busy_lock(lockres);
  
  	status = 0;
  bail:
  	return status;
  }
  
  static void user_dlm_recovery_handler_noop(int node_num,
  					   void *recovery_data)
  {
  	/* We ignore recovery events */
  	return;
  }
  
  void user_dlm_set_locking_protocol(void)
  {
  	ocfs2_stack_glue_set_max_proto_version(&user_dlm_lproto.lp_max_version);
  }
  
  struct ocfs2_cluster_connection *user_dlm_register(struct qstr *name)
  {
  	int rc;
  	struct ocfs2_cluster_connection *conn;
  
  	rc = ocfs2_cluster_connect_agnostic(name->name, name->len,
  					    &user_dlm_lproto,
  					    user_dlm_recovery_handler_noop,
  					    NULL, &conn);
  	if (rc)
  		mlog_errno(rc);
  
  	return rc ? ERR_PTR(rc) : conn;
  }
  
  void user_dlm_unregister(struct ocfs2_cluster_connection *conn)
  {
  	ocfs2_cluster_disconnect(conn, 0);
  }