fs/afs/dir_silly.c - linux - Git at Google

 // 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"

 /*
  * 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_fs_cursor fc;
 	struct afs_status_cb *scb;
 	int ret = -ERESTARTSYS;

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

 	scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
 	if (!scb)
 		return -ENOMEM;

 	trace_afs_silly_rename(vnode, false);
 	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
 		afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;

 		while (afs_select_fileserver(&fc)) {
 			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
 			afs_fs_rename(&fc, old->d_name.name,
 				      dvnode, new->d_name.name,
 				      scb, scb);
 		}

 		afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
 					&dir_data_version, scb);
 		ret = afs_end_vnode_operation(&fc);
 	}

 	if (ret == 0) {
 		spin_lock(&old->d_lock);
 		old->d_flags |= DCACHE_NFSFS_RENAMED;
 		spin_unlock(&old->d_lock);
 		if (dvnode->silly_key != key) {
 			key_put(dvnode->silly_key);
 			dvnode->silly_key = key_get(key);
 		}

 		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
 			afs_edit_dir_remove(dvnode, &old->d_name,
 					    afs_edit_dir_for_silly_0);
 		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
 			afs_edit_dir_add(dvnode, &new->d_name,
 					 &vnode->fid, afs_edit_dir_for_silly_1);

 		/* vfs_unlink and the like do not issue this when a file is
 		 * sillyrenamed, so do it here.
 		 */
 		fsnotify_nameremove(old, 0);
 	}

 	kfree(scb);
 	_leave(" = %d", ret);
 	return ret;
 }

 /**
  * 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. */
 		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;
 }

 /*
  * 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_fs_cursor fc;
 	struct afs_status_cb *scb;
 	int ret = -ERESTARTSYS;

 	_enter("");

 	scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
 	if (!scb)
 		return -ENOMEM;

 	trace_afs_silly_rename(vnode, true);
 	if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
 		afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;

 		while (afs_select_fileserver(&fc)) {
 			fc.cb_break = afs_calc_vnode_cb_break(dvnode);

 			if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
 			    !test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
 				yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
 						    &scb[0], &scb[1]);
 				if (fc.ac.error != -ECONNABORTED ||
 				    fc.ac.abort_code != RXGEN_OPCODE)
 					continue;
 				set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
 			}

 			afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
 		}

 		afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
 					&dir_data_version, &scb[0]);
 		ret = afs_end_vnode_operation(&fc);
 		if (ret == 0) {
 			drop_nlink(&vnode->vfs_inode);
 			if (vnode->vfs_inode.i_nlink == 0) {
 				set_bit(AFS_VNODE_DELETED, &vnode->flags);
 				clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
 			}
 		}
 		if (ret == 0 &&
 		    test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
 			afs_edit_dir_remove(dvnode, &dentry->d_name,
 					    afs_edit_dir_for_unlink);
 	}

 	kfree(scb);
 	_leave(" = %d", ret);
 	return ret;
 }

 /*
  * 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;
 }
	// 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"

	/*
	* 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_fs_cursor fc;
	struct afs_status_cb *scb;
	int ret = -ERESTARTSYS;

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

	scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
	if (!scb)
	return -ENOMEM;

	trace_afs_silly_rename(vnode, false);
	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
	afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;

	while (afs_select_fileserver(&fc)) {
	fc.cb_break = afs_calc_vnode_cb_break(dvnode);
	afs_fs_rename(&fc, old->d_name.name,
	dvnode, new->d_name.name,
	scb, scb);
	}

	afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
	&dir_data_version, scb);
	ret = afs_end_vnode_operation(&fc);
	}

	if (ret == 0) {
	spin_lock(&old->d_lock);
	old->d_flags \|= DCACHE_NFSFS_RENAMED;
	spin_unlock(&old->d_lock);
	if (dvnode->silly_key != key) {
	key_put(dvnode->silly_key);
	dvnode->silly_key = key_get(key);
	}

	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
	afs_edit_dir_remove(dvnode, &old->d_name,
	afs_edit_dir_for_silly_0);
	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
	afs_edit_dir_add(dvnode, &new->d_name,
	&vnode->fid, afs_edit_dir_for_silly_1);

	/* vfs_unlink and the like do not issue this when a file is
	* sillyrenamed, so do it here.
	*/
	fsnotify_nameremove(old, 0);
	}

	kfree(scb);
	_leave(" = %d", ret);
	return ret;
	}

	/**
	* 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. */
	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;
	}

	/*
	* 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_fs_cursor fc;
	struct afs_status_cb *scb;
	int ret = -ERESTARTSYS;

	_enter("");

	scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
	if (!scb)
	return -ENOMEM;

	trace_afs_silly_rename(vnode, true);
	if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
	afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;

	while (afs_select_fileserver(&fc)) {
	fc.cb_break = afs_calc_vnode_cb_break(dvnode);

	if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
	!test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
	yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
	&scb[0], &scb[1]);
	if (fc.ac.error != -ECONNABORTED \|\|
	fc.ac.abort_code != RXGEN_OPCODE)
	continue;
	set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
	}

	afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
	}

	afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
	&dir_data_version, &scb[0]);
	ret = afs_end_vnode_operation(&fc);
	if (ret == 0) {
	drop_nlink(&vnode->vfs_inode);
	if (vnode->vfs_inode.i_nlink == 0) {
	set_bit(AFS_VNODE_DELETED, &vnode->flags);
	clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
	}
	}
	if (ret == 0 &&
	test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))
	afs_edit_dir_remove(dvnode, &dentry->d_name,
	afs_edit_dir_for_unlink);
	}

	kfree(scb);
	_leave(" = %d", ret);
	return ret;
	}

	/*
	* 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;
	}