/*
   *  linux/fs/nfs/unlink.c
   *
   * nfs sillydelete handling
   *
   */
  
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/dcache.h>
  #include <linux/sunrpc/sched.h>
  #include <linux/sunrpc/clnt.h>
  #include <linux/nfs_fs.h>
  #include <linux/sched.h>
  #include <linux/wait.h>
  #include <linux/namei.h>
  
  #include "internal.h"
  #include "nfs4_fs.h"
  #include "iostat.h"
  #include "delegation.h"
  
  #include "nfstrace.h"
  
  /**
   * nfs_free_unlinkdata - release data from a sillydelete operation.
   * @data: pointer to unlink structure.
   */
  static void
  nfs_free_unlinkdata(struct nfs_unlinkdata *data)
  {
  	iput(data->dir);
  	put_rpccred(data->cred);
  	kfree(data->args.name.name);
  	kfree(data);
  }
  
  #define NAME_ALLOC_LEN(len)	((len+16) & ~15)
  /**
   * nfs_copy_dname - copy dentry name to data structure
   * @dentry: pointer to dentry
   * @data: nfs_unlinkdata
   */
  static int nfs_copy_dname(struct dentry *dentry, struct nfs_unlinkdata *data)
  {
  	char		*str;
  	int		len = dentry->d_name.len;
  
  	str = kmemdup(dentry->d_name.name, NAME_ALLOC_LEN(len), GFP_KERNEL);
  	if (!str)
  		return -ENOMEM;
  	data->args.name.len = len;
  	data->args.name.name = str;
  	return 0;
  }
  
  static void nfs_free_dname(struct nfs_unlinkdata *data)
  {
  	kfree(data->args.name.name);
  	data->args.name.name = NULL;
  	data->args.name.len = 0;
  }
  
  static void nfs_dec_sillycount(struct inode *dir)
  {
  	struct nfs_inode *nfsi = NFS_I(dir);
  	if (atomic_dec_return(&nfsi->silly_count) == 1)
  		wake_up(&nfsi->waitqueue);
  }
  
  /**
   * nfs_async_unlink_done - Sillydelete post-processing
   * @task: rpc_task of the sillydelete
   *
   * Do the directory attribute update.
   */
  static void nfs_async_unlink_done(struct rpc_task *task, void *calldata)
  {
  	struct nfs_unlinkdata *data = calldata;
  	struct inode *dir = data->dir;
  
  	trace_nfs_sillyrename_unlink(data, task->tk_status);
  	if (!NFS_PROTO(dir)->unlink_done(task, dir))
  		rpc_restart_call_prepare(task);
  }
  
  /**
   * nfs_async_unlink_release - Release the sillydelete data.
   * @task: rpc_task of the sillydelete
   *
   * We need to call nfs_put_unlinkdata as a 'tk_release' task since the
   * rpc_task would be freed too.
   */
  static void nfs_async_unlink_release(void *calldata)
  {
  	struct nfs_unlinkdata	*data = calldata;
  	struct super_block *sb = data->dir->i_sb;
  
  	nfs_dec_sillycount(data->dir);
  	nfs_free_unlinkdata(data);
  	nfs_sb_deactive(sb);
  }
  
  static void nfs_unlink_prepare(struct rpc_task *task, void *calldata)
  {
  	struct nfs_unlinkdata *data = calldata;
  	NFS_PROTO(data->dir)->unlink_rpc_prepare(task, data);
  }
  
  static const struct rpc_call_ops nfs_unlink_ops = {
  	.rpc_call_done = nfs_async_unlink_done,
  	.rpc_release = nfs_async_unlink_release,
  	.rpc_call_prepare = nfs_unlink_prepare,
  };
  
  static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct nfs_unlinkdata *data)
  {
  	struct rpc_message msg = {
  		.rpc_argp = &data->args,
  		.rpc_resp = &data->res,
  		.rpc_cred = data->cred,
  	};
  	struct rpc_task_setup task_setup_data = {
  		.rpc_message = &msg,
  		.callback_ops = &nfs_unlink_ops,
  		.callback_data = data,
  		.workqueue = nfsiod_workqueue,
  		.flags = RPC_TASK_ASYNC,
  	};
  	struct rpc_task *task;
  	struct dentry *alias;
  
  	alias = d_lookup(parent, &data->args.name);
  	if (alias != NULL) {
  		int ret;
  		void *devname_garbage = NULL;
  
  		/*
  		 * Hey, we raced with lookup... See if we need to transfer
  		 * the sillyrename information to the aliased dentry.
  		 */
  		nfs_free_dname(data);
  		ret = nfs_copy_dname(alias, data);
  		spin_lock(&alias->d_lock);
  		if (ret == 0 && alias->d_inode != NULL &&
  		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
  			devname_garbage = alias->d_fsdata;
  			alias->d_fsdata = data;
  			alias->d_flags |= DCACHE_NFSFS_RENAMED;
  			ret = 1;
  		} else
  			ret = 0;
  		spin_unlock(&alias->d_lock);
  		nfs_dec_sillycount(dir);
  		dput(alias);
  		/*
  		 * If we'd displaced old cached devname, free it.  At that
  		 * point dentry is definitely not a root, so we won't need
  		 * that anymore.
  		 */
  		kfree(devname_garbage);
  		return ret;
  	}
  	data->dir = igrab(dir);
  	if (!data->dir) {
  		nfs_dec_sillycount(dir);
  		return 0;
  	}
  	nfs_sb_active(dir->i_sb);
  	data->args.fh = NFS_FH(dir);
  	nfs_fattr_init(data->res.dir_attr);
  
  	NFS_PROTO(dir)->unlink_setup(&msg, dir);
  
  	task_setup_data.rpc_client = NFS_CLIENT(dir);
  	task = rpc_run_task(&task_setup_data);
  	if (!IS_ERR(task))
  		rpc_put_task_async(task);
  	return 1;
  }
  
  static int nfs_call_unlink(struct dentry *dentry, struct nfs_unlinkdata *data)
  {
  	struct dentry *parent;
  	struct inode *dir;
  	int ret = 0;
  
  
  	parent = dget_parent(dentry);
  	if (parent == NULL)
  		goto out_free;
  	dir = parent->d_inode;
  	/* Non-exclusive lock protects against concurrent lookup() calls */
  	spin_lock(&dir->i_lock);
  	if (atomic_inc_not_zero(&NFS_I(dir)->silly_count) == 0) {
  		/* Deferred delete */
  		hlist_add_head(&data->list, &NFS_I(dir)->silly_list);
  		spin_unlock(&dir->i_lock);
  		ret = 1;
  		goto out_dput;
  	}
  	spin_unlock(&dir->i_lock);
  	ret = nfs_do_call_unlink(parent, dir, data);
  out_dput:
  	dput(parent);
  out_free:
  	return ret;
  }
  
  void nfs_wait_on_sillyrename(struct dentry *dentry)
  {
  	struct nfs_inode *nfsi = NFS_I(dentry->d_inode);
  
  	wait_event(nfsi->waitqueue, atomic_read(&nfsi->silly_count) <= 1);
  }
  
  void nfs_block_sillyrename(struct dentry *dentry)
  {
  	struct nfs_inode *nfsi = NFS_I(dentry->d_inode);
  
  	wait_event(nfsi->waitqueue, atomic_cmpxchg(&nfsi->silly_count, 1, 0) == 1);
  }
  
  void nfs_unblock_sillyrename(struct dentry *dentry)
  {
  	struct inode *dir = dentry->d_inode;
  	struct nfs_inode *nfsi = NFS_I(dir);
  	struct nfs_unlinkdata *data;
  
  	atomic_inc(&nfsi->silly_count);
  	spin_lock(&dir->i_lock);
  	while (!hlist_empty(&nfsi->silly_list)) {
  		if (!atomic_inc_not_zero(&nfsi->silly_count))
  			break;
  		data = hlist_entry(nfsi->silly_list.first, struct nfs_unlinkdata, list);
  		hlist_del(&data->list);
  		spin_unlock(&dir->i_lock);
  		if (nfs_do_call_unlink(dentry, dir, data) == 0)
  			nfs_free_unlinkdata(data);
  		spin_lock(&dir->i_lock);
  	}
  	spin_unlock(&dir->i_lock);
  }
  
  /**
   * nfs_async_unlink - asynchronous unlinking of a file
   * @dir: parent directory of dentry
   * @dentry: dentry to unlink
   */
  static int
  nfs_async_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct nfs_unlinkdata *data;
  	int status = -ENOMEM;
  	void *devname_garbage = NULL;
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (data == NULL)
  		goto out;
  
  	data->cred = rpc_lookup_cred();
  	if (IS_ERR(data->cred)) {
  		status = PTR_ERR(data->cred);
  		goto out_free;
  	}
  	data->res.dir_attr = &data->dir_attr;
  
  	status = -EBUSY;
  	spin_lock(&dentry->d_lock);
  	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
  		goto out_unlock;
  	dentry->d_flags |= DCACHE_NFSFS_RENAMED;
  	devname_garbage = dentry->d_fsdata;
  	dentry->d_fsdata = data;
  	spin_unlock(&dentry->d_lock);
  	/*
  	 * If we'd displaced old cached devname, free it.  At that
  	 * point dentry is definitely not a root, so we won't need
  	 * that anymore.
  	 */
  	kfree(devname_garbage);
  	return 0;
  out_unlock:
  	spin_unlock(&dentry->d_lock);
  	put_rpccred(data->cred);
  out_free:
  	kfree(data);
  out:
  	return status;
  }
  
  /**
   * nfs_complete_unlink - Initialize completion of the sillydelete
   * @dentry: dentry to delete
   * @inode: inode
   *
   * Since we're most likely to be called by dentry_iput(), we
   * only use the dentry to find the sillydelete. We then copy the name
   * into the qstr.
   */
  void
  nfs_complete_unlink(struct dentry *dentry, struct inode *inode)
  {
  	struct nfs_unlinkdata	*data = NULL;
  
  	spin_lock(&dentry->d_lock);
  	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
  		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
  		data = dentry->d_fsdata;
  		dentry->d_fsdata = NULL;
  	}
  	spin_unlock(&dentry->d_lock);
  
  	if (data != NULL && (NFS_STALE(inode) || !nfs_call_unlink(dentry, data)))
  		nfs_free_unlinkdata(data);
  }
  
  /* Cancel a queued async unlink. Called when a sillyrename run fails. */
  static void
  nfs_cancel_async_unlink(struct dentry *dentry)
  {
  	spin_lock(&dentry->d_lock);
  	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
  		struct nfs_unlinkdata *data = dentry->d_fsdata;
  
  		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
  		dentry->d_fsdata = NULL;
  		spin_unlock(&dentry->d_lock);
  		nfs_free_unlinkdata(data);
  		return;
  	}
  	spin_unlock(&dentry->d_lock);
  }
  
  /**
   * nfs_async_rename_done - Sillyrename post-processing
   * @task: rpc_task of the sillyrename
   * @calldata: nfs_renamedata for the sillyrename
   *
   * Do the directory attribute updates and the d_move
   */
  static void nfs_async_rename_done(struct rpc_task *task, void *calldata)
  {
  	struct nfs_renamedata *data = calldata;
  	struct inode *old_dir = data->old_dir;
  	struct inode *new_dir = data->new_dir;
  	struct dentry *old_dentry = data->old_dentry;
  
  	trace_nfs_sillyrename_rename(old_dir, old_dentry,
  			new_dir, data->new_dentry, task->tk_status);
  	if (!NFS_PROTO(old_dir)->rename_done(task, old_dir, new_dir)) {
  		rpc_restart_call_prepare(task);
  		return;
  	}
  
  	if (task->tk_status != 0)
  		nfs_cancel_async_unlink(old_dentry);
  }
  
  /**
   * nfs_async_rename_release - Release the sillyrename data.
   * @calldata: the struct nfs_renamedata to be released
   */
  static void nfs_async_rename_release(void *calldata)
  {
  	struct nfs_renamedata	*data = calldata;
  	struct super_block *sb = data->old_dir->i_sb;
  
  	if (data->old_dentry->d_inode)
  		nfs_mark_for_revalidate(data->old_dentry->d_inode);
  
  	dput(data->old_dentry);
  	dput(data->new_dentry);
  	iput(data->old_dir);
  	iput(data->new_dir);
  	nfs_sb_deactive(sb);
  	put_rpccred(data->cred);
  	kfree(data);
  }
  
  static void nfs_rename_prepare(struct rpc_task *task, void *calldata)
  {
  	struct nfs_renamedata *data = calldata;
  	NFS_PROTO(data->old_dir)->rename_rpc_prepare(task, data);
  }
  
  static const struct rpc_call_ops nfs_rename_ops = {
  	.rpc_call_done = nfs_async_rename_done,
  	.rpc_release = nfs_async_rename_release,
  	.rpc_call_prepare = nfs_rename_prepare,
  };
  
  /**
   * nfs_async_rename - perform an asynchronous rename operation
   * @old_dir: directory that currently holds the dentry to be renamed
   * @new_dir: target directory for the rename
   * @old_dentry: original dentry to be renamed
   * @new_dentry: dentry to which the old_dentry should be renamed
   *
   * It's expected that valid references to the dentries and inodes are held
   */
  static struct rpc_task *
  nfs_async_rename(struct inode *old_dir, struct inode *new_dir,
  		 struct dentry *old_dentry, struct dentry *new_dentry)
  {
  	struct nfs_renamedata *data;
  	struct rpc_message msg = { };
  	struct rpc_task_setup task_setup_data = {
  		.rpc_message = &msg,
  		.callback_ops = &nfs_rename_ops,
  		.workqueue = nfsiod_workqueue,
  		.rpc_client = NFS_CLIENT(old_dir),
  		.flags = RPC_TASK_ASYNC,
  	};
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (data == NULL)
  		return ERR_PTR(-ENOMEM);
  	task_setup_data.callback_data = data;
  
  	data->cred = rpc_lookup_cred();
  	if (IS_ERR(data->cred)) {
  		struct rpc_task *task = ERR_CAST(data->cred);
  		kfree(data);
  		return task;
  	}
  
  	msg.rpc_argp = &data->args;
  	msg.rpc_resp = &data->res;
  	msg.rpc_cred = data->cred;
  
  	/* set up nfs_renamedata */
  	data->old_dir = old_dir;
  	ihold(old_dir);
  	data->new_dir = new_dir;
  	ihold(new_dir);
  	data->old_dentry = dget(old_dentry);
  	data->new_dentry = dget(new_dentry);
  	nfs_fattr_init(&data->old_fattr);
  	nfs_fattr_init(&data->new_fattr);
  
  	/* set up nfs_renameargs */
  	data->args.old_dir = NFS_FH(old_dir);
  	data->args.old_name = &old_dentry->d_name;
  	data->args.new_dir = NFS_FH(new_dir);
  	data->args.new_name = &new_dentry->d_name;
  
  	/* set up nfs_renameres */
  	data->res.old_fattr = &data->old_fattr;
  	data->res.new_fattr = &data->new_fattr;
  
  	nfs_sb_active(old_dir->i_sb);
  
  	NFS_PROTO(data->old_dir)->rename_setup(&msg, old_dir);
  
  	return rpc_run_task(&task_setup_data);
  }
  
  #define SILLYNAME_PREFIX ".nfs"
  #define SILLYNAME_PREFIX_LEN ((unsigned)sizeof(SILLYNAME_PREFIX) - 1)
  #define SILLYNAME_FILEID_LEN ((unsigned)sizeof(u64) << 1)
  #define SILLYNAME_COUNTER_LEN ((unsigned)sizeof(unsigned int) << 1)
  #define SILLYNAME_LEN (SILLYNAME_PREFIX_LEN + \
  		SILLYNAME_FILEID_LEN + \
  		SILLYNAME_COUNTER_LEN)
  
  /**
   * nfs_sillyrename - Perform a silly-rename of a dentry
   * @dir: inode of directory that contains dentry
   * @dentry: dentry to be sillyrenamed
   *
   * NFSv2/3 is stateless and the server doesn't know when the client is
   * holding a file open. To prevent application problems when a file is
   * unlinked while it's still open, the client performs a "silly-rename".
   * That is, it renames the file to a hidden file in the same directory,
   * and only performs the unlink once the last reference to it is put.
   *
   * The final cleanup is done during dentry_iput.
   *
   * (Note: NFSv4 is stateful, and has opens, so in theory an NFSv4 server
   * could take responsibility for keeping open files referenced.  The server
   * would also need to ensure that opened-but-deleted files were kept over
   * reboots.  However, we may not assume a server does so.  (RFC 5661
   * does provide an OPEN4_RESULT_PRESERVE_UNLINKED flag that a server can
   * use to advertise that it does this; some day we may take advantage of
   * it.))
   */
  int
  nfs_sillyrename(struct inode *dir, struct dentry *dentry)
  {
  	static unsigned int sillycounter;
  	unsigned char silly[SILLYNAME_LEN + 1];
  	unsigned long long fileid;
  	struct dentry *sdentry;
  	struct rpc_task *task;
  	int            error = -EBUSY;
  
  	dfprintk(VFS, "NFS: silly-rename(%pd2, ct=%d)
  ",
  		dentry, d_count(dentry));
  	nfs_inc_stats(dir, NFSIOS_SILLYRENAME);
  
  	/*
  	 * We don't allow a dentry to be silly-renamed twice.
  	 */
  	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
  		goto out;
  
  	fileid = NFS_FILEID(dentry->d_inode);
  
  	/* Return delegation in anticipation of the rename */
  	NFS_PROTO(dentry->d_inode)->return_delegation(dentry->d_inode);
  
  	sdentry = NULL;
  	do {
  		int slen;
  		dput(sdentry);
  		sillycounter++;
  		slen = scnprintf(silly, sizeof(silly),
  				SILLYNAME_PREFIX "%0*llx%0*x",
  				SILLYNAME_FILEID_LEN, fileid,
  				SILLYNAME_COUNTER_LEN, sillycounter);
  
  		dfprintk(VFS, "NFS: trying to rename %pd to %s
  ",
  				dentry, silly);
  
  		sdentry = lookup_one_len(silly, dentry->d_parent, slen);
  		/*
  		 * N.B. Better to return EBUSY here ... it could be
  		 * dangerous to delete the file while it's in use.
  		 */
  		if (IS_ERR(sdentry))
  			goto out;
  	} while (sdentry->d_inode != NULL); /* need negative lookup */
  
  	/* queue unlink first. Can't do this from rpc_release as it
  	 * has to allocate memory
  	 */
  	error = nfs_async_unlink(dir, dentry);
  	if (error)
  		goto out_dput;
  
  	/* populate unlinkdata with the right dname */
  	error = nfs_copy_dname(sdentry,
  				(struct nfs_unlinkdata *)dentry->d_fsdata);
  	if (error) {
  		nfs_cancel_async_unlink(dentry);
  		goto out_dput;
  	}
  
  	/* run the rename task, undo unlink if it fails */
  	task = nfs_async_rename(dir, dir, dentry, sdentry);
  	if (IS_ERR(task)) {
  		error = -EBUSY;
  		nfs_cancel_async_unlink(dentry);
  		goto out_dput;
  	}
  
  	/* wait for the RPC task to complete, unless a SIGKILL intervenes */
  	error = rpc_wait_for_completion_task(task);
  	if (error == 0)
  		error = task->tk_status;
  	switch (error) {
  	case 0:
  		/* The rename succeeded */
  		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  		d_move(dentry, sdentry);
  		break;
  	case -ERESTARTSYS:
  		/* The result of the rename is unknown. Play it safe by
  		 * forcing a new lookup */
  		d_drop(dentry);
  		d_drop(sdentry);
  	}
  	rpc_put_task(task);
  out_dput:
  	dput(sdentry);
  out:
  	return error;
  }