/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * dcache.c
   *
   * dentry cache handling code
   *
   * 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.
   */
  
  #include <linux/fs.h>
  #include <linux/types.h>
  #include <linux/slab.h>
  #include <linux/namei.h>

  #include <cluster/masklog.h>
  
  #include "ocfs2.h"
  
  #include "alloc.h"
  #include "dcache.h"

  #include "dlmglue.h"

  #include "file.h"
  #include "inode.h"

  #include "super.h"

  #include "ocfs2_trace.h"

  void ocfs2_dentry_attach_gen(struct dentry *dentry)
  {
  	unsigned long gen =
  		OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
  	BUG_ON(dentry->d_inode);
  	dentry->d_fsdata = (void *)gen;
  }

  static int ocfs2_dentry_revalidate(struct dentry *dentry,
  				   struct nameidata *nd)
  {

  	struct inode *inode;

  	int ret = 0;    /* if all else fails, just return false */

  	struct ocfs2_super *osb;

  	if (nd && nd->flags & LOOKUP_RCU)

  		return -ECHILD;
  
  	inode = dentry->d_inode;
  	osb = OCFS2_SB(dentry->d_sb);

  	trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
  				      dentry->d_name.name);

  	/* For a negative dentry -
  	 * check the generation number of the parent and compare with the
  	 * one stored in the inode.
  	 */

  	if (inode == NULL) {

  		unsigned long gen = (unsigned long) dentry->d_fsdata;
  		unsigned long pgen =
  			OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;

  
  		trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
  						       dentry->d_name.name,
  						       pgen, gen);

  		if (gen != pgen)
  			goto bail;
  		goto valid;

  	}

  	BUG_ON(!osb);

  	if (inode == osb->root_inode || is_bad_inode(inode))
  		goto bail;
  
  	spin_lock(&OCFS2_I(inode)->ip_lock);
  	/* did we or someone else delete this inode? */
  	if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {

  		spin_unlock(&OCFS2_I(inode)->ip_lock);

  		trace_ocfs2_dentry_revalidate_delete(
  				(unsigned long long)OCFS2_I(inode)->ip_blkno);

  		goto bail;
  	}
  	spin_unlock(&OCFS2_I(inode)->ip_lock);

  	/*
  	 * We don't need a cluster lock to test this because once an
  	 * inode nlink hits zero, it never goes back.
  	 */
  	if (inode->i_nlink == 0) {

  		trace_ocfs2_dentry_revalidate_orphaned(
  			(unsigned long long)OCFS2_I(inode)->ip_blkno,
  			S_ISDIR(inode->i_mode));

  		goto bail;

  	}

  	/*
  	 * If the last lookup failed to create dentry lock, let us
  	 * redo it.
  	 */
  	if (!dentry->d_fsdata) {

  		trace_ocfs2_dentry_revalidate_nofsdata(
  				(unsigned long long)OCFS2_I(inode)->ip_blkno);

  		goto bail;
  	}

  valid:

  	ret = 1;
  
  bail:

  	trace_ocfs2_dentry_revalidate_ret(ret);

  	return ret;
  }

  static int ocfs2_match_dentry(struct dentry *dentry,
  			      u64 parent_blkno,
  			      int skip_unhashed)
  {
  	struct inode *parent;
  
  	/*
  	 * ocfs2_lookup() does a d_splice_alias() _before_ attaching
  	 * to the lock data, so we skip those here, otherwise
  	 * ocfs2_dentry_attach_lock() will get its original dentry
  	 * back.
  	 */
  	if (!dentry->d_fsdata)
  		return 0;
  
  	if (!dentry->d_parent)
  		return 0;
  
  	if (skip_unhashed && d_unhashed(dentry))
  		return 0;
  
  	parent = dentry->d_parent->d_inode;
  	/* Negative parent dentry? */
  	if (!parent)
  		return 0;
  
  	/* Name is in a different directory. */
  	if (OCFS2_I(parent)->ip_blkno != parent_blkno)
  		return 0;
  
  	return 1;
  }
  
  /*
   * Walk the inode alias list, and find a dentry which has a given
   * parent. ocfs2_dentry_attach_lock() wants to find _any_ alias as it

   * is looking for a dentry_lock reference. The downconvert thread is
   * looking to unhash aliases, so we allow it to skip any that already
   * have that property.

   */
  struct dentry *ocfs2_find_local_alias(struct inode *inode,
  				      u64 parent_blkno,
  				      int skip_unhashed)
  {
  	struct list_head *p;
  	struct dentry *dentry = NULL;

  	spin_lock(&inode->i_lock);

  	list_for_each(p, &inode->i_dentry) {
  		dentry = list_entry(p, struct dentry, d_alias);

  		spin_lock(&dentry->d_lock);

  		if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {

  			trace_ocfs2_find_local_alias(dentry->d_name.len,
  						     dentry->d_name.name);

  			dget_dlock(dentry);

  			spin_unlock(&dentry->d_lock);

  			break;
  		}

  		spin_unlock(&dentry->d_lock);

  
  		dentry = NULL;
  	}

  	spin_unlock(&inode->i_lock);

  
  	return dentry;
  }

  DEFINE_SPINLOCK(dentry_attach_lock);

  /*
   * Attach this dentry to a cluster lock.
   *
   * Dentry locks cover all links in a given directory to a particular
   * inode. We do this so that ocfs2 can build a lock name which all
   * nodes in the cluster can agree on at all times. Shoving full names
   * in the cluster lock won't work due to size restrictions. Covering
   * links inside of a directory is a good compromise because it still
   * allows us to use the parent directory lock to synchronize
   * operations.
   *
   * Call this function with the parent dir semaphore and the parent dir
   * cluster lock held.
   *
   * The dir semaphore will protect us from having to worry about
   * concurrent processes on our node trying to attach a lock at the
   * same time.
   *
   * The dir cluster lock (held at either PR or EX mode) protects us
   * from unlink and rename on other nodes.
   *

   * A dput() can happen asynchronously due to pruning, so we cover
   * attaching and detaching the dentry lock with a
   * dentry_attach_lock.
   *
   * A node which has done lookup on a name retains a protected read
   * lock until final dput. If the user requests and unlink or rename,
   * the protected read is upgraded to an exclusive lock. Other nodes
   * who have seen the dentry will then be informed that they need to
   * downgrade their lock, which will involve d_delete on the
   * dentry. This happens in ocfs2_dentry_convert_worker().
   */
  int ocfs2_dentry_attach_lock(struct dentry *dentry,
  			     struct inode *inode,

  			     u64 parent_blkno)

  {
  	int ret;
  	struct dentry *alias;
  	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;

  	trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
  				       (unsigned long long)parent_blkno, dl);

  
  	/*
  	 * Negative dentry. We ignore these for now.
  	 *
  	 * XXX: Could we can improve ocfs2_dentry_revalidate() by
  	 * tracking these?
  	 */
  	if (!inode)
  		return 0;

  	if (!dentry->d_inode && dentry->d_fsdata) {
  		/* Converting a negative dentry to positive
  		   Clear dentry->d_fsdata */
  		dentry->d_fsdata = dl = NULL;
  	}

  	if (dl) {
  		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
  				" \"%.*s\": old parent: %llu, new: %llu
  ",
  				dentry->d_name.len, dentry->d_name.name,
  				(unsigned long long)parent_blkno,
  				(unsigned long long)dl->dl_parent_blkno);
  		return 0;
  	}
  
  	alias = ocfs2_find_local_alias(inode, parent_blkno, 0);
  	if (alias) {
  		/*
  		 * Great, an alias exists, which means we must have a
  		 * dentry lock already. We can just grab the lock off
  		 * the alias and add it to the list.
  		 *
  		 * We're depending here on the fact that this dentry
  		 * was found and exists in the dcache and so must have
  		 * a reference to the dentry_lock because we can't
  		 * race creates. Final dput() cannot happen on it
  		 * since we have it pinned, so our reference is safe.
  		 */
  		dl = alias->d_fsdata;

  		mlog_bug_on_msg(!dl, "parent %llu, ino %llu
  ",

  				(unsigned long long)parent_blkno,

  				(unsigned long long)OCFS2_I(inode)->ip_blkno);

  
  		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
  				" \"%.*s\": old parent: %llu, new: %llu
  ",
  				dentry->d_name.len, dentry->d_name.name,
  				(unsigned long long)parent_blkno,
  				(unsigned long long)dl->dl_parent_blkno);

  		trace_ocfs2_dentry_attach_lock_found(dl->dl_lockres.l_name,
  				(unsigned long long)parent_blkno,
  				(unsigned long long)OCFS2_I(inode)->ip_blkno);

  
  		goto out_attach;
  	}
  
  	/*
  	 * There are no other aliases
  	 */
  	dl = kmalloc(sizeof(*dl), GFP_NOFS);
  	if (!dl) {
  		ret = -ENOMEM;
  		mlog_errno(ret);
  		return ret;
  	}
  
  	dl->dl_count = 0;
  	/*
  	 * Does this have to happen below, for all attaches, in case

  	 * the struct inode gets blown away by the downconvert thread?

  	 */
  	dl->dl_inode = igrab(inode);
  	dl->dl_parent_blkno = parent_blkno;
  	ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);
  
  out_attach:
  	spin_lock(&dentry_attach_lock);
  	dentry->d_fsdata = dl;
  	dl->dl_count++;
  	spin_unlock(&dentry_attach_lock);
  
  	/*

  	 * This actually gets us our PRMODE level lock. From now on,
  	 * we'll have a notification if one of these names is
  	 * destroyed on another node.
  	 */
  	ret = ocfs2_dentry_lock(dentry, 0);

  	if (!ret)
  		ocfs2_dentry_unlock(dentry, 0);
  	else

  		mlog_errno(ret);

  	/*
  	 * In case of error, manually free the allocation and do the iput().
  	 * We need to do this because error here means no d_instantiate(),
  	 * which means iput() will not be called during dput(dentry).
  	 */
  	if (ret < 0 && !alias) {
  		ocfs2_lock_res_free(&dl->dl_lockres);
  		BUG_ON(dl->dl_count != 1);
  		spin_lock(&dentry_attach_lock);
  		dentry->d_fsdata = NULL;
  		spin_unlock(&dentry_attach_lock);
  		kfree(dl);
  		iput(inode);
  	}

  	dput(alias);
  
  	return ret;
  }

  DEFINE_SPINLOCK(dentry_list_lock);

  
  /* We limit the number of dentry locks to drop in one go. We have
   * this limit so that we don't starve other users of ocfs2_wq. */
  #define DL_INODE_DROP_COUNT 64
  
  /* Drop inode references from dentry locks */

  static void __ocfs2_drop_dl_inodes(struct ocfs2_super *osb, int drop_count)

  {

  	struct ocfs2_dentry_lock *dl;

  
  	spin_lock(&dentry_list_lock);

  	while (osb->dentry_lock_list && (drop_count < 0 || drop_count--)) {

  		dl = osb->dentry_lock_list;
  		osb->dentry_lock_list = dl->dl_next;
  		spin_unlock(&dentry_list_lock);
  		iput(dl->dl_inode);
  		kfree(dl);
  		spin_lock(&dentry_list_lock);
  	}

  	spin_unlock(&dentry_list_lock);
  }
  
  void ocfs2_drop_dl_inodes(struct work_struct *work)
  {
  	struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
  					       dentry_lock_work);
  
  	__ocfs2_drop_dl_inodes(osb, DL_INODE_DROP_COUNT);
  	/*
  	 * Don't queue dropping if umount is in progress. We flush the
  	 * list in ocfs2_dismount_volume
  	 */
  	spin_lock(&dentry_list_lock);
  	if (osb->dentry_lock_list &&
  	    !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))

  		queue_work(ocfs2_wq, &osb->dentry_lock_work);
  	spin_unlock(&dentry_list_lock);
  }

  /* Flush the whole work queue */
  void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
  {
  	__ocfs2_drop_dl_inodes(osb, -1);
  }

  /*
   * ocfs2_dentry_iput() and friends.
   *
   * At this point, our particular dentry is detached from the inodes
   * alias list, so there's no way that the locking code can find it.
   *
   * The interesting stuff happens when we determine that our lock needs
   * to go away because this is the last subdir alias in the
   * system. This function needs to handle a couple things:
   *
   * 1) Synchronizing lock shutdown with the downconvert threads. This
   *    is already handled for us via the lockres release drop function
   *    called in ocfs2_release_dentry_lock()
   *
   * 2) A race may occur when we're doing our lock shutdown and
   *    another process wants to create a new dentry lock. Right now we
   *    let them race, which means that for a very short while, this
   *    node might have two locks on a lock resource. This should be a
   *    problem though because one of them is in the process of being
   *    thrown out.
   */
  static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
  				   struct ocfs2_dentry_lock *dl)
  {
  	ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
  	ocfs2_lock_res_free(&dl->dl_lockres);

  
  	/* We leave dropping of inode reference to ocfs2_wq as that can
  	 * possibly lead to inode deletion which gets tricky */
  	spin_lock(&dentry_list_lock);

  	if (!osb->dentry_lock_list &&
  	    !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))

  		queue_work(ocfs2_wq, &osb->dentry_lock_work);
  	dl->dl_next = osb->dentry_lock_list;
  	osb->dentry_lock_list = dl;
  	spin_unlock(&dentry_list_lock);

  }
  
  void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
  			   struct ocfs2_dentry_lock *dl)
  {

  	int unlock;

  
  	BUG_ON(dl->dl_count == 0);
  
  	spin_lock(&dentry_attach_lock);
  	dl->dl_count--;
  	unlock = !dl->dl_count;
  	spin_unlock(&dentry_attach_lock);
  
  	if (unlock)
  		ocfs2_drop_dentry_lock(osb, dl);
  }
  
  static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
  {
  	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;

  	if (!dl) {
  		/*
  		 * No dentry lock is ok if we're disconnected or
  		 * unhashed.
  		 */
  		if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
  		    !d_unhashed(dentry)) {
  			unsigned long long ino = 0ULL;
  			if (inode)
  				ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
  			mlog(ML_ERROR, "Dentry is missing cluster lock. "
  			     "inode: %llu, d_flags: 0x%x, d_name: %.*s
  ",
  			     ino, dentry->d_flags, dentry->d_name.len,
  			     dentry->d_name.name);
  		}

  		goto out;

  	}

  
  	mlog_bug_on_msg(dl->dl_count == 0, "dentry: %.*s, count: %u
  ",
  			dentry->d_name.len, dentry->d_name.name,
  			dl->dl_count);
  
  	ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);
  
  out:
  	iput(inode);
  }
  
  /*
   * d_move(), but keep the locks in sync.
   *
   * When we are done, "dentry" will have the parent dir and name of
   * "target", which will be thrown away.
   *
   * We manually update the lock of "dentry" if need be.
   *
   * "target" doesn't have it's dentry lock touched - we allow the later
   * dput() to handle this for us.
   *
   * This is called during ocfs2_rename(), while holding parent
   * directory locks. The dentries have already been deleted on other
   * nodes via ocfs2_remote_dentry_delete().
   *

   * Normally, the VFS handles the d_move() for the file system, after

   * the ->rename() callback. OCFS2 wants to handle this internally, so
   * the new lock can be created atomically with respect to the cluster.
   */
  void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
  		       struct inode *old_dir, struct inode *new_dir)
  {
  	int ret;
  	struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
  	struct inode *inode = dentry->d_inode;
  
  	/*
  	 * Move within the same directory, so the actual lock info won't
  	 * change.
  	 *
  	 * XXX: Is there any advantage to dropping the lock here?
  	 */
  	if (old_dir == new_dir)

  		goto out_move;

  
  	ocfs2_dentry_lock_put(osb, dentry->d_fsdata);
  
  	dentry->d_fsdata = NULL;

  	ret = ocfs2_dentry_attach_lock(dentry, inode, OCFS2_I(new_dir)->ip_blkno);

  	if (ret)
  		mlog_errno(ret);

  
  out_move:
  	d_move(dentry, target);

  }

  const struct dentry_operations ocfs2_dentry_ops = {

  	.d_revalidate		= ocfs2_dentry_revalidate,

  	.d_iput			= ocfs2_dentry_iput,

  };