// SPDX-License-Identifier: GPL-2.0-or-later

  /* AFS silly rename handling
   *
   * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   * - Derived from NFS's sillyrename.

   */
  
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/namei.h>
  #include <linux/fsnotify.h>
  #include "internal.h"

  static void afs_silly_rename_success(struct afs_operation *op)
  {
  	_enter("op=%08x", op->debug_id);

  	afs_check_dir_conflict(op, &op->file[0]);

  	afs_vnode_commit_status(op, &op->file[0]);
  }
  
  static void afs_silly_rename_edit_dir(struct afs_operation *op)
  {
  	struct afs_vnode_param *dvp = &op->file[0];
  	struct afs_vnode *dvnode = dvp->vnode;
  	struct afs_vnode *vnode = AFS_FS_I(d_inode(op->dentry));
  	struct dentry *old = op->dentry;
  	struct dentry *new = op->dentry_2;
  
  	spin_lock(&old->d_lock);
  	old->d_flags |= DCACHE_NFSFS_RENAMED;
  	spin_unlock(&old->d_lock);
  	if (dvnode->silly_key != op->key) {
  		key_put(dvnode->silly_key);
  		dvnode->silly_key = key_get(op->key);
  	}
  
  	down_write(&dvnode->validate_lock);
  	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
  	    dvnode->status.data_version == dvp->dv_before + dvp->dv_delta) {
  		afs_edit_dir_remove(dvnode, &old->d_name,
  				    afs_edit_dir_for_silly_0);
  		afs_edit_dir_add(dvnode, &new->d_name,
  				 &vnode->fid, afs_edit_dir_for_silly_1);
  	}
  	up_write(&dvnode->validate_lock);
  }
  
  static const struct afs_operation_ops afs_silly_rename_operation = {
  	.issue_afs_rpc	= afs_fs_rename,
  	.issue_yfs_rpc	= yfs_fs_rename,
  	.success	= afs_silly_rename_success,
  	.edit_dir	= afs_silly_rename_edit_dir,
  };

  /*
   * Actually perform the silly rename step.
   */
  static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  			       struct dentry *old, struct dentry *new,
  			       struct key *key)
  {

  	struct afs_operation *op;

  
  	_enter("%pd,%pd", old, new);

  	op = afs_alloc_operation(key, dvnode->volume);
  	if (IS_ERR(op))
  		return PTR_ERR(op);

  	afs_op_set_vnode(op, 0, dvnode);

  	afs_op_set_vnode(op, 1, dvnode);
  	op->file[0].dv_delta = 1;
  	op->file[1].dv_delta = 1;
  	op->file[0].update_ctime = true;
  	op->file[1].update_ctime = true;

  	op->dentry		= old;
  	op->dentry_2		= new;
  	op->ops			= &afs_silly_rename_operation;

  	trace_afs_silly_rename(vnode, false);
  	return afs_do_sync_operation(op);

  }
  
  /**
   * afs_sillyrename - Perform a silly-rename of a dentry
   *
   * AFS 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.
   */
  int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  		    struct dentry *dentry, struct key *key)
  {
  	static unsigned int sillycounter;
  	struct dentry *sdentry = NULL;
  	unsigned char silly[16];
  	int ret = -EBUSY;
  
  	_enter("");
  
  	/* We don't allow a dentry to be silly-renamed twice. */
  	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
  		return -EBUSY;
  
  	sdentry = NULL;
  	do {
  		int slen;
  
  		dput(sdentry);
  		sillycounter++;
  
  		/* Create a silly name.  Note that the ".__afs" prefix is
  		 * understood by the salvager and must not be changed.
  		 */
  		slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
  		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 (!d_is_negative(sdentry));
  
  	ihold(&vnode->vfs_inode);
  
  	ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
  	switch (ret) {
  	case 0:
  		/* The rename succeeded. */

  		set_bit(AFS_VNODE_SILLY_DELETED, &vnode->flags);

  		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);
  	}
  
  	iput(&vnode->vfs_inode);
  	dput(sdentry);
  out:
  	_leave(" = %d", ret);
  	return ret;
  }

  static void afs_silly_unlink_success(struct afs_operation *op)
  {

  	_enter("op=%08x", op->debug_id);

  	afs_check_dir_conflict(op, &op->file[0]);

  	afs_vnode_commit_status(op, &op->file[0]);
  	afs_vnode_commit_status(op, &op->file[1]);
  	afs_update_dentry_version(op, &op->file[0], op->dentry);

  }
  
  static void afs_silly_unlink_edit_dir(struct afs_operation *op)
  {
  	struct afs_vnode_param *dvp = &op->file[0];
  	struct afs_vnode *dvnode = dvp->vnode;
  
  	_enter("op=%08x", op->debug_id);
  	down_write(&dvnode->validate_lock);
  	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
  	    dvnode->status.data_version == dvp->dv_before + dvp->dv_delta)
  		afs_edit_dir_remove(dvnode, &op->dentry->d_name,
  				    afs_edit_dir_for_unlink);
  	up_write(&dvnode->validate_lock);
  }
  
  static const struct afs_operation_ops afs_silly_unlink_operation = {
  	.issue_afs_rpc	= afs_fs_remove_file,
  	.issue_yfs_rpc	= yfs_fs_remove_file,
  	.success	= afs_silly_unlink_success,

  	.aborted	= afs_check_for_remote_deletion,

  	.edit_dir	= afs_silly_unlink_edit_dir,
  };

  /*
   * Tell the server to remove a sillyrename file.
   */
  static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
  			       struct dentry *dentry, struct key *key)
  {

  	struct afs_operation *op;

  
  	_enter("");

  	op = afs_alloc_operation(NULL, dvnode->volume);
  	if (IS_ERR(op))
  		return PTR_ERR(op);

  	afs_op_set_vnode(op, 0, dvnode);
  	afs_op_set_vnode(op, 1, vnode);

  	op->file[0].dv_delta = 1;
  	op->file[0].update_ctime = true;
  	op->file[1].op_unlinked = true;
  	op->file[1].update_ctime = true;

  	op->dentry	= dentry;
  	op->ops		= &afs_silly_unlink_operation;
  
  	trace_afs_silly_rename(vnode, true);

  	afs_begin_vnode_operation(op);
  	afs_wait_for_operation(op);
  
  	/* If there was a conflict with a third party, check the status of the
  	 * unlinked vnode.
  	 */
  	if (op->error == 0 && (op->flags & AFS_OPERATION_DIR_CONFLICT)) {
  		op->file[1].update_ctime = false;
  		op->fetch_status.which = 1;
  		op->ops = &afs_fetch_status_operation;
  		afs_begin_vnode_operation(op);
  		afs_wait_for_operation(op);
  	}
  
  	return afs_put_operation(op);

  }
  
  /*
   * Remove sillyrename file on iput.
   */
  int afs_silly_iput(struct dentry *dentry, struct inode *inode)
  {
  	struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
  	struct afs_vnode *vnode = AFS_FS_I(inode);
  	struct dentry *alias;
  	int ret;
  
  	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
  
  	_enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
  
  	down_read(&dvnode->rmdir_lock);
  
  	alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
  	if (IS_ERR(alias)) {
  		up_read(&dvnode->rmdir_lock);
  		return 0;
  	}
  
  	if (!d_in_lookup(alias)) {
  		/* We raced with lookup...  See if we need to transfer the
  		 * sillyrename information to the aliased dentry.
  		 */
  		ret = 0;
  		spin_lock(&alias->d_lock);
  		if (d_really_is_positive(alias) &&
  		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
  			alias->d_flags |= DCACHE_NFSFS_RENAMED;
  			ret = 1;
  		}
  		spin_unlock(&alias->d_lock);
  		up_read(&dvnode->rmdir_lock);
  		dput(alias);
  		return ret;
  	}
  
  	/* Stop lock-release from complaining. */
  	spin_lock(&vnode->lock);
  	vnode->lock_state = AFS_VNODE_LOCK_DELETED;
  	trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
  	spin_unlock(&vnode->lock);
  
  	afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
  	up_read(&dvnode->rmdir_lock);
  	d_lookup_done(alias);
  	dput(alias);
  	return 1;
  }