fs/cachefiles/namei.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* CacheFiles path walking and related routines
  *
  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

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

 /*
  * Mark the backing file as being a cache file if it's not already in use.  The
  * mark tells the culling request command that it's not allowed to cull the
  * file or directory.  The caller must hold the inode lock.
  */
 static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
 					   struct inode *inode)
 {
 	bool can_use = false;

 	if (!(inode->i_flags & S_KERNEL_FILE)) {
 		inode->i_flags |= S_KERNEL_FILE;
 		trace_cachefiles_mark_active(object, inode);
 		can_use = true;
 	} else {
 		trace_cachefiles_mark_failed(object, inode);
 	}

 	return can_use;
 }

 static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
 					 struct inode *inode)
 {
 	bool can_use;

 	inode_lock(inode);
 	can_use = __cachefiles_mark_inode_in_use(object, inode);
 	inode_unlock(inode);
 	return can_use;
 }

 /*
  * Unmark a backing inode.  The caller must hold the inode lock.
  */
 static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
 					     struct inode *inode)
 {
 	inode->i_flags &= ~S_KERNEL_FILE;
 	trace_cachefiles_mark_inactive(object, inode);
 }

 static void cachefiles_do_unmark_inode_in_use(struct cachefiles_object *object,
 					      struct inode *inode)
 {
 	inode_lock(inode);
 	__cachefiles_unmark_inode_in_use(object, inode);
 	inode_unlock(inode);
 }

 /*
  * Unmark a backing inode and tell cachefilesd that there's something that can
  * be culled.
  */
 void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
 				    struct file *file)
 {
 	struct cachefiles_cache *cache = object->volume->cache;
 	struct inode *inode = file_inode(file);

 	cachefiles_do_unmark_inode_in_use(object, inode);

 	if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 		atomic_long_add(inode->i_blocks, &cache->b_released);
 		if (atomic_inc_return(&cache->f_released))
 			cachefiles_state_changed(cache);
 	}
 }

 /*
  * get a subdirectory
  */
 struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 					struct dentry *dir,
 					const char *dirname,
 					bool *_is_new)
 {
 	struct dentry *subdir;
 	struct path path;
 	int ret;

 	_enter(",,%s", dirname);

 	/* search the current directory for the element name */
 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

 retry:
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
 		subdir = lookup_one_len(dirname, dir, strlen(dirname));
 	else
 		subdir = ERR_PTR(ret);
 	trace_cachefiles_lookup(NULL, dir, subdir);
 	if (IS_ERR(subdir)) {
 		trace_cachefiles_vfs_error(NULL, d_backing_inode(dir),
 					   PTR_ERR(subdir),
 					   cachefiles_trace_lookup_error);
 		if (PTR_ERR(subdir) == -ENOMEM)
 			goto nomem_d_alloc;
 		goto lookup_error;
 	}

 	_debug("subdir -> %pd %s",
 	       subdir, d_backing_inode(subdir) ? "positive" : "negative");

 	/* we need to create the subdir if it doesn't exist yet */
 	if (d_is_negative(subdir)) {
 		ret = cachefiles_has_space(cache, 1, 0,
 					   cachefiles_has_space_for_create);
 		if (ret < 0)
 			goto mkdir_error;

 		_debug("attempt mkdir");

 		path.mnt = cache->mnt;
 		path.dentry = dir;
 		ret = security_path_mkdir(&path, subdir, 0700);
 		if (ret < 0)
 			goto mkdir_error;
 		ret = cachefiles_inject_write_error();
 		if (ret == 0)
 			ret = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700);
 		if (ret < 0) {
 			trace_cachefiles_vfs_error(NULL, d_inode(dir), ret,
 						   cachefiles_trace_mkdir_error);
 			goto mkdir_error;
 		}
 		trace_cachefiles_mkdir(dir, subdir);

 		if (unlikely(d_unhashed(subdir))) {
 			cachefiles_put_directory(subdir);
 			goto retry;
 		}
 		ASSERT(d_backing_inode(subdir));

 		_debug("mkdir -> %pd{ino=%lu}",
 		       subdir, d_backing_inode(subdir)->i_ino);
 		if (_is_new)
 			*_is_new = true;
 	}

 	/* Tell rmdir() it's not allowed to delete the subdir */
 	inode_lock(d_inode(subdir));
 	inode_unlock(d_inode(dir));

 	if (!__cachefiles_mark_inode_in_use(NULL, d_inode(subdir))) {
 		pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
 			  subdir, d_inode(subdir)->i_ino);
 		goto mark_error;
 	}

 	inode_unlock(d_inode(subdir));

 	/* we need to make sure the subdir is a directory */
 	ASSERT(d_backing_inode(subdir));

 	if (!d_can_lookup(subdir)) {
 		pr_err("%s is not a directory\n", dirname);
 		ret = -EIO;
 		goto check_error;
 	}

 	ret = -EPERM;
 	if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) ||
 	    !d_backing_inode(subdir)->i_op->lookup ||
 	    !d_backing_inode(subdir)->i_op->mkdir ||
 	    !d_backing_inode(subdir)->i_op->rename ||
 	    !d_backing_inode(subdir)->i_op->rmdir ||
 	    !d_backing_inode(subdir)->i_op->unlink)
 		goto check_error;

 	_leave(" = [%lu]", d_backing_inode(subdir)->i_ino);
 	return subdir;

 check_error:
 	cachefiles_put_directory(subdir);
 	_leave(" = %d [check]", ret);
 	return ERR_PTR(ret);

 mark_error:
 	inode_unlock(d_inode(subdir));
 	dput(subdir);
 	return ERR_PTR(-EBUSY);

 mkdir_error:
 	inode_unlock(d_inode(dir));
 	dput(subdir);
 	pr_err("mkdir %s failed with error %d\n", dirname, ret);
 	return ERR_PTR(ret);

 lookup_error:
 	inode_unlock(d_inode(dir));
 	ret = PTR_ERR(subdir);
 	pr_err("Lookup %s failed with error %d\n", dirname, ret);
 	return ERR_PTR(ret);

 nomem_d_alloc:
 	inode_unlock(d_inode(dir));
 	_leave(" = -ENOMEM");
 	return ERR_PTR(-ENOMEM);
 }

 /*
  * Put a subdirectory.
  */
 void cachefiles_put_directory(struct dentry *dir)
 {
 	if (dir) {
 		cachefiles_do_unmark_inode_in_use(NULL, d_inode(dir));
 		dput(dir);
 	}
 }

 /*
  * Remove a regular file from the cache.
  */
 static int cachefiles_unlink(struct cachefiles_cache *cache,
 			     struct cachefiles_object *object,
 			     struct dentry *dir, struct dentry *dentry,
 			     enum fscache_why_object_killed why)
 {
 	struct path path = {
 		.mnt	= cache->mnt,
 		.dentry	= dir,
 	};
 	int ret;

 	trace_cachefiles_unlink(object, d_inode(dentry)->i_ino, why);
 	ret = security_path_unlink(&path, dentry);
 	if (ret < 0) {
 		cachefiles_io_error(cache, "Unlink security error");
 		return ret;
 	}

 	ret = cachefiles_inject_remove_error();
 	if (ret == 0) {
 		ret = vfs_unlink(&nop_mnt_idmap, d_backing_inode(dir), dentry, NULL);
 		if (ret == -EIO)
 			cachefiles_io_error(cache, "Unlink failed");
 	}
 	if (ret != 0)
 		trace_cachefiles_vfs_error(object, d_backing_inode(dir), ret,
 					   cachefiles_trace_unlink_error);
 	return ret;
 }

 /*
  * Delete an object representation from the cache
  * - File backed objects are unlinked
  * - Directory backed objects are stuffed into the graveyard for userspace to
  *   delete
  */
 int cachefiles_bury_object(struct cachefiles_cache *cache,
 			   struct cachefiles_object *object,
 			   struct dentry *dir,
 			   struct dentry *rep,
 			   enum fscache_why_object_killed why)
 {
 	struct dentry *grave, *trap;
 	struct path path, path_to_graveyard;
 	char nbuffer[8 + 8 + 1];
 	int ret;

 	_enter(",'%pd','%pd'", dir, rep);

 	if (rep->d_parent != dir) {
 		inode_unlock(d_inode(dir));
 		_leave(" = -ESTALE");
 		return -ESTALE;
 	}

 	/* non-directories can just be unlinked */
 	if (!d_is_dir(rep)) {
 		dget(rep); /* Stop the dentry being negated if it's only pinned
 			    * by a file struct.
 			    */
 		ret = cachefiles_unlink(cache, object, dir, rep, why);
 		dput(rep);

 		inode_unlock(d_inode(dir));
 		_leave(" = %d", ret);
 		return ret;
 	}

 	/* directories have to be moved to the graveyard */
 	_debug("move stale object to graveyard");
 	inode_unlock(d_inode(dir));

 try_again:
 	/* first step is to make up a grave dentry in the graveyard */
 	sprintf(nbuffer, "%08x%08x",
 		(uint32_t) ktime_get_real_seconds(),
 		(uint32_t) atomic_inc_return(&cache->gravecounter));

 	/* do the multiway lock magic */
 	trap = lock_rename(cache->graveyard, dir);
 	if (IS_ERR(trap))
 		return PTR_ERR(trap);

 	/* do some checks before getting the grave dentry */
 	if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
 		/* the entry was probably culled when we dropped the parent dir
 		 * lock */
 		unlock_rename(cache->graveyard, dir);
 		_leave(" = 0 [culled?]");
 		return 0;
 	}

 	if (!d_can_lookup(cache->graveyard)) {
 		unlock_rename(cache->graveyard, dir);
 		cachefiles_io_error(cache, "Graveyard no longer a directory");
 		return -EIO;
 	}

 	if (trap == rep) {
 		unlock_rename(cache->graveyard, dir);
 		cachefiles_io_error(cache, "May not make directory loop");
 		return -EIO;
 	}

 	if (d_mountpoint(rep)) {
 		unlock_rename(cache->graveyard, dir);
 		cachefiles_io_error(cache, "Mountpoint in cache");
 		return -EIO;
 	}

 	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
 	if (IS_ERR(grave)) {
 		unlock_rename(cache->graveyard, dir);
 		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
 					   PTR_ERR(grave),
 					   cachefiles_trace_lookup_error);

 		if (PTR_ERR(grave) == -ENOMEM) {
 			_leave(" = -ENOMEM");
 			return -ENOMEM;
 		}

 		cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
 		return -EIO;
 	}

 	if (d_is_positive(grave)) {
 		unlock_rename(cache->graveyard, dir);
 		dput(grave);
 		grave = NULL;
 		cond_resched();
 		goto try_again;
 	}

 	if (d_mountpoint(grave)) {
 		unlock_rename(cache->graveyard, dir);
 		dput(grave);
 		cachefiles_io_error(cache, "Mountpoint in graveyard");
 		return -EIO;
 	}

 	/* target should not be an ancestor of source */
 	if (trap == grave) {
 		unlock_rename(cache->graveyard, dir);
 		dput(grave);
 		cachefiles_io_error(cache, "May not make directory loop");
 		return -EIO;
 	}

 	/* attempt the rename */
 	path.mnt = cache->mnt;
 	path.dentry = dir;
 	path_to_graveyard.mnt = cache->mnt;
 	path_to_graveyard.dentry = cache->graveyard;
 	ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
 	if (ret < 0) {
 		cachefiles_io_error(cache, "Rename security error %d", ret);
 	} else {
 		struct renamedata rd = {
 			.old_mnt_idmap	= &nop_mnt_idmap,
 			.old_dir	= d_inode(dir),
 			.old_dentry	= rep,
 			.new_mnt_idmap	= &nop_mnt_idmap,
 			.new_dir	= d_inode(cache->graveyard),
 			.new_dentry	= grave,
 		};
 		trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
 			ret = vfs_rename(&rd);
 		if (ret != 0)
 			trace_cachefiles_vfs_error(object, d_inode(dir), ret,
 						   cachefiles_trace_rename_error);
 		if (ret != 0 && ret != -ENOMEM)
 			cachefiles_io_error(cache,
 					    "Rename failed with error %d", ret);
 	}

 	__cachefiles_unmark_inode_in_use(object, d_inode(rep));
 	unlock_rename(cache->graveyard, dir);
 	dput(grave);
 	_leave(" = 0");
 	return 0;
 }

 /*
  * Delete a cache file.
  */
 int cachefiles_delete_object(struct cachefiles_object *object,
 			     enum fscache_why_object_killed why)
 {
 	struct cachefiles_volume *volume = object->volume;
 	struct dentry *dentry = object->file->f_path.dentry;
 	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
 	int ret;

 	_enter(",OBJ%x{%pD}", object->debug_id, object->file);

 	/* Stop the dentry being negated if it's only pinned by a file struct. */
 	dget(dentry);

 	inode_lock_nested(d_backing_inode(fan), I_MUTEX_PARENT);
 	ret = cachefiles_unlink(volume->cache, object, fan, dentry, why);
 	inode_unlock(d_backing_inode(fan));
 	dput(dentry);
 	return ret;
 }

 /*
  * Create a temporary file and leave it unattached and un-xattr'd until the
  * time comes to discard the object from memory.
  */
 struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 {
 	struct cachefiles_volume *volume = object->volume;
 	struct cachefiles_cache *cache = volume->cache;
 	const struct cred *saved_cred;
 	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
 	struct file *file;
 	const struct path parentpath = { .mnt = cache->mnt, .dentry = fan };
 	uint64_t ni_size;
 	long ret;


 	cachefiles_begin_secure(cache, &saved_cred);

 	ret = cachefiles_inject_write_error();
 	if (ret == 0) {
 		file = kernel_tmpfile_open(&nop_mnt_idmap, &parentpath,
 					   S_IFREG | 0600,
 					   O_RDWR | O_LARGEFILE | O_DIRECT,
 					   cache->cache_cred);
 		ret = PTR_ERR_OR_ZERO(file);
 	}
 	if (ret) {
 		trace_cachefiles_vfs_error(object, d_inode(fan), ret,
 					   cachefiles_trace_tmpfile_error);
 		if (ret == -EIO)
 			cachefiles_io_error_obj(object, "Failed to create tmpfile");
 		goto err;
 	}

 	trace_cachefiles_tmpfile(object, file_inode(file));

 	/* This is a newly created file with no other possible user */
 	if (!cachefiles_mark_inode_in_use(object, file_inode(file)))
 		WARN_ON(1);

 	ret = cachefiles_ondemand_init_object(object);
 	if (ret < 0)
 		goto err_unuse;

 	ni_size = object->cookie->object_size;
 	ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);

 	if (ni_size > 0) {
 		trace_cachefiles_trunc(object, file_inode(file), 0, ni_size,
 				       cachefiles_trunc_expand_tmpfile);
 		ret = cachefiles_inject_write_error();
 		if (ret == 0)
 			ret = vfs_truncate(&file->f_path, ni_size);
 		if (ret < 0) {
 			trace_cachefiles_vfs_error(
 				object, file_inode(file), ret,
 				cachefiles_trace_trunc_error);
 			goto err_unuse;
 		}
 	}

 	ret = -EINVAL;
 	if (unlikely(!file->f_op->read_iter) ||
 	    unlikely(!file->f_op->write_iter)) {
 		fput(file);
 		pr_notice("Cache does not support read_iter and write_iter\n");
 		goto err_unuse;
 	}
 out:
 	cachefiles_end_secure(cache, saved_cred);
 	return file;

 err_unuse:
 	cachefiles_do_unmark_inode_in_use(object, file_inode(file));
 	fput(file);
 err:
 	file = ERR_PTR(ret);
 	goto out;
 }

 /*
  * Create a new file.
  */
 static bool cachefiles_create_file(struct cachefiles_object *object)
 {
 	struct file *file;
 	int ret;

 	ret = cachefiles_has_space(object->volume->cache, 1, 0,
 				   cachefiles_has_space_for_create);
 	if (ret < 0)
 		return false;

 	file = cachefiles_create_tmpfile(object);
 	if (IS_ERR(file))
 		return false;

 	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
 	set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 	_debug("create -> %pD{ino=%lu}", file, file_inode(file)->i_ino);
 	object->file = file;
 	return true;
 }

 /*
  * Open an existing file, checking its attributes and replacing it if it is
  * stale.
  */
 static bool cachefiles_open_file(struct cachefiles_object *object,
 				 struct dentry *dentry)
 {
 	struct cachefiles_cache *cache = object->volume->cache;
 	struct file *file;
 	struct path path;
 	int ret;

 	_enter("%pd", dentry);

 	if (!cachefiles_mark_inode_in_use(object, d_inode(dentry))) {
 		pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
 			  dentry, d_inode(dentry)->i_ino);
 		return false;
 	}

 	/* We need to open a file interface onto a data file now as we can't do
 	 * it on demand because writeback called from do_exit() sees
 	 * current->fs == NULL - which breaks d_path() called from ext4 open.
 	 */
 	path.mnt = cache->mnt;
 	path.dentry = dentry;
 	file = kernel_file_open(&path, O_RDWR | O_LARGEFILE | O_DIRECT, cache->cache_cred);
 	if (IS_ERR(file)) {
 		trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
 					   PTR_ERR(file),
 					   cachefiles_trace_open_error);
 		goto error;
 	}

 	if (unlikely(!file->f_op->read_iter) ||
 	    unlikely(!file->f_op->write_iter)) {
 		pr_notice("Cache does not support read_iter and write_iter\n");
 		goto error_fput;
 	}
 	_debug("file -> %pd positive", dentry);

 	ret = cachefiles_ondemand_init_object(object);
 	if (ret < 0)
 		goto error_fput;

 	ret = cachefiles_check_auxdata(object, file);
 	if (ret < 0)
 		goto check_failed;

 	clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &object->cookie->flags);

 	object->file = file;

 	/* Always update the atime on an object we've just looked up (this is
 	 * used to keep track of culling, and atimes are only updated by read,
 	 * write and readdir but not lookup or open).
 	 */
 	touch_atime(&file->f_path);
 	return true;

 check_failed:
 	fscache_cookie_lookup_negative(object->cookie);
 	cachefiles_unmark_inode_in_use(object, file);
 	fput(file);
 	if (ret == -ESTALE)
 		return cachefiles_create_file(object);
 	return false;

 error_fput:
 	fput(file);
 error:
 	cachefiles_do_unmark_inode_in_use(object, d_inode(dentry));
 	return false;
 }

 /*
  * walk from the parent object to the child object through the backing
  * filesystem, creating directories as we go
  */
 bool cachefiles_look_up_object(struct cachefiles_object *object)
 {
 	struct cachefiles_volume *volume = object->volume;
 	struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
 	int ret;

 	_enter("OBJ%x,%s,", object->debug_id, object->d_name);

 	/* Look up path "cache/vol/fanout/file". */
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
 		dentry = lookup_positive_unlocked(object->d_name, fan,
 						  object->d_name_len);
 	else
 		dentry = ERR_PTR(ret);
 	trace_cachefiles_lookup(object, fan, dentry);
 	if (IS_ERR(dentry)) {
 		if (dentry == ERR_PTR(-ENOENT))
 			goto new_file;
 		if (dentry == ERR_PTR(-EIO))
 			cachefiles_io_error_obj(object, "Lookup failed");
 		return false;
 	}

 	if (!d_is_reg(dentry)) {
 		pr_err("%pd is not a file\n", dentry);
 		inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 		ret = cachefiles_bury_object(volume->cache, object, fan, dentry,
 					     FSCACHE_OBJECT_IS_WEIRD);
 		dput(dentry);
 		if (ret < 0)
 			return false;
 		goto new_file;
 	}

 	ret = cachefiles_open_file(object, dentry);
 	dput(dentry);
 	if (!ret)
 		return false;

 	_leave(" = t [%lu]", file_inode(object->file)->i_ino);
 	return true;

 new_file:
 	fscache_cookie_lookup_negative(object->cookie);
 	return cachefiles_create_file(object);
 }

 /*
  * Attempt to link a temporary file into its rightful place in the cache.
  */
 bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 			       struct cachefiles_object *object)
 {
 	struct cachefiles_volume *volume = object->volume;
 	struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
 	bool success = false;
 	int ret;

 	_enter(",%pD", object->file);

 	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
 		dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
 	else
 		dentry = ERR_PTR(ret);
 	if (IS_ERR(dentry)) {
 		trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
 					   cachefiles_trace_lookup_error);
 		_debug("lookup fail %ld", PTR_ERR(dentry));
 		goto out_unlock;
 	}

 	if (!d_is_negative(dentry)) {
 		ret = cachefiles_unlink(volume->cache, object, fan, dentry,
 					FSCACHE_OBJECT_IS_STALE);
 		if (ret < 0)
 			goto out_dput;

 		dput(dentry);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
 			dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
 		else
 			dentry = ERR_PTR(ret);
 		if (IS_ERR(dentry)) {
 			trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
 						   cachefiles_trace_lookup_error);
 			_debug("lookup fail %ld", PTR_ERR(dentry));
 			goto out_unlock;
 		}
 	}

 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
 		ret = vfs_link(object->file->f_path.dentry, &nop_mnt_idmap,
 			       d_inode(fan), dentry, NULL);
 	if (ret < 0) {
 		trace_cachefiles_vfs_error(object, d_inode(fan), ret,
 					   cachefiles_trace_link_error);
 		_debug("link fail %d", ret);
 	} else {
 		trace_cachefiles_link(object, file_inode(object->file));
 		spin_lock(&object->lock);
 		/* TODO: Do we want to switch the file pointer to the new dentry? */
 		clear_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 		spin_unlock(&object->lock);
 		success = true;
 	}

 out_dput:
 	dput(dentry);
 out_unlock:
 	inode_unlock(d_inode(fan));
 	_leave(" = %u", success);
 	return success;
 }

 /*
  * Look up an inode to be checked or culled.  Return -EBUSY if the inode is
  * marked in use.
  */
 static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
 						 struct dentry *dir,
 						 char *filename)
 {
 	struct dentry *victim;
 	int ret = -ENOENT;

 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

 	victim = lookup_one_len(filename, dir, strlen(filename));
 	if (IS_ERR(victim))
 		goto lookup_error;
 	if (d_is_negative(victim))
 		goto lookup_put;
 	if (d_inode(victim)->i_flags & S_KERNEL_FILE)
 		goto lookup_busy;
 	return victim;

 lookup_busy:
 	ret = -EBUSY;
 lookup_put:
 	inode_unlock(d_inode(dir));
 	dput(victim);
 	return ERR_PTR(ret);

 lookup_error:
 	inode_unlock(d_inode(dir));
 	ret = PTR_ERR(victim);
 	if (ret == -ENOENT)
 		return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */

 	if (ret == -EIO) {
 		cachefiles_io_error(cache, "Lookup failed");
 	} else if (ret != -ENOMEM) {
 		pr_err("Internal error: %d\n", ret);
 		ret = -EIO;
 	}

 	return ERR_PTR(ret);
 }

 /*
  * Cull an object if it's not in use
  * - called only by cache manager daemon
  */
 int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 		    char *filename)
 {
 	struct dentry *victim;
 	struct inode *inode;
 	int ret;

 	_enter(",%pd/,%s", dir, filename);

 	victim = cachefiles_lookup_for_cull(cache, dir, filename);
 	if (IS_ERR(victim))
 		return PTR_ERR(victim);

 	/* check to see if someone is using this object */
 	inode = d_inode(victim);
 	inode_lock(inode);
 	if (inode->i_flags & S_KERNEL_FILE) {
 		ret = -EBUSY;
 	} else {
 		/* Stop the cache from picking it back up */
 		inode->i_flags |= S_KERNEL_FILE;
 		ret = 0;
 	}
 	inode_unlock(inode);
 	if (ret < 0)
 		goto error_unlock;

 	ret = cachefiles_bury_object(cache, NULL, dir, victim,
 				     FSCACHE_OBJECT_WAS_CULLED);
 	if (ret < 0)
 		goto error;

 	fscache_count_culled();
 	dput(victim);
 	_leave(" = 0");
 	return 0;

 error_unlock:
 	inode_unlock(d_inode(dir));
 error:
 	dput(victim);
 	if (ret == -ENOENT)
 		return -ESTALE; /* Probably got retired by the netfs */

 	if (ret != -ENOMEM) {
 		pr_err("Internal error: %d\n", ret);
 		ret = -EIO;
 	}

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

 /*
  * Find out if an object is in use or not
  * - called only by cache manager daemon
  * - returns -EBUSY or 0 to indicate whether an object is in use or not
  */
 int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
 			    char *filename)
 {
 	struct dentry *victim;
 	int ret = 0;

 	victim = cachefiles_lookup_for_cull(cache, dir, filename);
 	if (IS_ERR(victim))
 		return PTR_ERR(victim);

 	inode_unlock(d_inode(dir));
 	dput(victim);
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* CacheFiles path walking and related routines
	*
	* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

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

	/*
	* Mark the backing file as being a cache file if it's not already in use. The
	* mark tells the culling request command that it's not allowed to cull the
	* file or directory. The caller must hold the inode lock.
	*/
	static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
	struct inode *inode)
	{
	bool can_use = false;

	if (!(inode->i_flags & S_KERNEL_FILE)) {
	inode->i_flags \|= S_KERNEL_FILE;
	trace_cachefiles_mark_active(object, inode);
	can_use = true;
	} else {
	trace_cachefiles_mark_failed(object, inode);
	}

	return can_use;
	}

	static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
	struct inode *inode)
	{
	bool can_use;

	inode_lock(inode);
	can_use = __cachefiles_mark_inode_in_use(object, inode);
	inode_unlock(inode);
	return can_use;
	}

	/*
	* Unmark a backing inode. The caller must hold the inode lock.
	*/
	static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
	struct inode *inode)
	{
	inode->i_flags &= ~S_KERNEL_FILE;
	trace_cachefiles_mark_inactive(object, inode);
	}

	static void cachefiles_do_unmark_inode_in_use(struct cachefiles_object *object,
	struct inode *inode)
	{
	inode_lock(inode);
	__cachefiles_unmark_inode_in_use(object, inode);
	inode_unlock(inode);
	}

	/*
	* Unmark a backing inode and tell cachefilesd that there's something that can
	* be culled.
	*/
	void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
	struct file *file)
	{
	struct cachefiles_cache *cache = object->volume->cache;
	struct inode *inode = file_inode(file);

	cachefiles_do_unmark_inode_in_use(object, inode);

	if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
	atomic_long_add(inode->i_blocks, &cache->b_released);
	if (atomic_inc_return(&cache->f_released))
	cachefiles_state_changed(cache);
	}
	}

	/*
	* get a subdirectory
	*/
	struct dentry cachefiles_get_directory(struct cachefiles_cache cache,
	struct dentry *dir,
	const char *dirname,
	bool *_is_new)
	{
	struct dentry *subdir;
	struct path path;
	int ret;

	_enter(",,%s", dirname);

	/* search the current directory for the element name */
	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

	retry:
	ret = cachefiles_inject_read_error();
	if (ret == 0)
	subdir = lookup_one_len(dirname, dir, strlen(dirname));
	else
	subdir = ERR_PTR(ret);
	trace_cachefiles_lookup(NULL, dir, subdir);
	if (IS_ERR(subdir)) {
	trace_cachefiles_vfs_error(NULL, d_backing_inode(dir),
	PTR_ERR(subdir),
	cachefiles_trace_lookup_error);
	if (PTR_ERR(subdir) == -ENOMEM)
	goto nomem_d_alloc;
	goto lookup_error;
	}

	_debug("subdir -> %pd %s",
	subdir, d_backing_inode(subdir) ? "positive" : "negative");

	/* we need to create the subdir if it doesn't exist yet */
	if (d_is_negative(subdir)) {
	ret = cachefiles_has_space(cache, 1, 0,
	cachefiles_has_space_for_create);
	if (ret < 0)
	goto mkdir_error;

	_debug("attempt mkdir");

	path.mnt = cache->mnt;
	path.dentry = dir;
	ret = security_path_mkdir(&path, subdir, 0700);
	if (ret < 0)
	goto mkdir_error;
	ret = cachefiles_inject_write_error();
	if (ret == 0)
	ret = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700);
	if (ret < 0) {
	trace_cachefiles_vfs_error(NULL, d_inode(dir), ret,
	cachefiles_trace_mkdir_error);
	goto mkdir_error;
	}
	trace_cachefiles_mkdir(dir, subdir);

	if (unlikely(d_unhashed(subdir))) {
	cachefiles_put_directory(subdir);
	goto retry;
	}
	ASSERT(d_backing_inode(subdir));

	_debug("mkdir -> %pd{ino=%lu}",
	subdir, d_backing_inode(subdir)->i_ino);
	if (_is_new)
	*_is_new = true;
	}

	/* Tell rmdir() it's not allowed to delete the subdir */
	inode_lock(d_inode(subdir));
	inode_unlock(d_inode(dir));

	if (!__cachefiles_mark_inode_in_use(NULL, d_inode(subdir))) {
	pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
	subdir, d_inode(subdir)->i_ino);
	goto mark_error;
	}

	inode_unlock(d_inode(subdir));

	/* we need to make sure the subdir is a directory */
	ASSERT(d_backing_inode(subdir));

	if (!d_can_lookup(subdir)) {
	pr_err("%s is not a directory\n", dirname);
	ret = -EIO;
	goto check_error;
	}

	ret = -EPERM;
	if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) \|\|
	!d_backing_inode(subdir)->i_op->lookup \|\|
	!d_backing_inode(subdir)->i_op->mkdir \|\|
	!d_backing_inode(subdir)->i_op->rename \|\|
	!d_backing_inode(subdir)->i_op->rmdir \|\|
	!d_backing_inode(subdir)->i_op->unlink)
	goto check_error;

	_leave(" = [%lu]", d_backing_inode(subdir)->i_ino);
	return subdir;

	check_error:
	cachefiles_put_directory(subdir);
	_leave(" = %d [check]", ret);
	return ERR_PTR(ret);

	mark_error:
	inode_unlock(d_inode(subdir));
	dput(subdir);
	return ERR_PTR(-EBUSY);

	mkdir_error:
	inode_unlock(d_inode(dir));
	dput(subdir);
	pr_err("mkdir %s failed with error %d\n", dirname, ret);
	return ERR_PTR(ret);

	lookup_error:
	inode_unlock(d_inode(dir));
	ret = PTR_ERR(subdir);
	pr_err("Lookup %s failed with error %d\n", dirname, ret);
	return ERR_PTR(ret);

	nomem_d_alloc:
	inode_unlock(d_inode(dir));
	_leave(" = -ENOMEM");
	return ERR_PTR(-ENOMEM);
	}

	/*
	* Put a subdirectory.
	*/
	void cachefiles_put_directory(struct dentry *dir)
	{
	if (dir) {
	cachefiles_do_unmark_inode_in_use(NULL, d_inode(dir));
	dput(dir);
	}
	}

	/*
	* Remove a regular file from the cache.
	*/
	static int cachefiles_unlink(struct cachefiles_cache *cache,
	struct cachefiles_object *object,
	struct dentry dir, struct dentry dentry,
	enum fscache_why_object_killed why)
	{
	struct path path = {
	.mnt = cache->mnt,
	.dentry = dir,
	};
	int ret;

	trace_cachefiles_unlink(object, d_inode(dentry)->i_ino, why);
	ret = security_path_unlink(&path, dentry);
	if (ret < 0) {
	cachefiles_io_error(cache, "Unlink security error");
	return ret;
	}

	ret = cachefiles_inject_remove_error();
	if (ret == 0) {
	ret = vfs_unlink(&nop_mnt_idmap, d_backing_inode(dir), dentry, NULL);
	if (ret == -EIO)
	cachefiles_io_error(cache, "Unlink failed");
	}
	if (ret != 0)
	trace_cachefiles_vfs_error(object, d_backing_inode(dir), ret,
	cachefiles_trace_unlink_error);
	return ret;
	}

	/*
	* Delete an object representation from the cache
	* - File backed objects are unlinked
	* - Directory backed objects are stuffed into the graveyard for userspace to
	* delete
	*/
	int cachefiles_bury_object(struct cachefiles_cache *cache,
	struct cachefiles_object *object,
	struct dentry *dir,
	struct dentry *rep,
	enum fscache_why_object_killed why)
	{
	struct dentry grave, trap;
	struct path path, path_to_graveyard;
	char nbuffer[8 + 8 + 1];
	int ret;

	_enter(",'%pd','%pd'", dir, rep);

	if (rep->d_parent != dir) {
	inode_unlock(d_inode(dir));
	_leave(" = -ESTALE");
	return -ESTALE;
	}

	/* non-directories can just be unlinked */
	if (!d_is_dir(rep)) {
	dget(rep); /* Stop the dentry being negated if it's only pinned
	* by a file struct.
	*/
	ret = cachefiles_unlink(cache, object, dir, rep, why);
	dput(rep);

	inode_unlock(d_inode(dir));
	_leave(" = %d", ret);
	return ret;
	}

	/* directories have to be moved to the graveyard */
	_debug("move stale object to graveyard");
	inode_unlock(d_inode(dir));

	try_again:
	/* first step is to make up a grave dentry in the graveyard */
	sprintf(nbuffer, "%08x%08x",
	(uint32_t) ktime_get_real_seconds(),
	(uint32_t) atomic_inc_return(&cache->gravecounter));

	/* do the multiway lock magic */
	trap = lock_rename(cache->graveyard, dir);
	if (IS_ERR(trap))
	return PTR_ERR(trap);

	/* do some checks before getting the grave dentry */
	if (rep->d_parent != dir \|\| IS_DEADDIR(d_inode(rep))) {
	/* the entry was probably culled when we dropped the parent dir
	* lock */
	unlock_rename(cache->graveyard, dir);
	_leave(" = 0 [culled?]");
	return 0;
	}

	if (!d_can_lookup(cache->graveyard)) {
	unlock_rename(cache->graveyard, dir);
	cachefiles_io_error(cache, "Graveyard no longer a directory");
	return -EIO;
	}

	if (trap == rep) {
	unlock_rename(cache->graveyard, dir);
	cachefiles_io_error(cache, "May not make directory loop");
	return -EIO;
	}

	if (d_mountpoint(rep)) {
	unlock_rename(cache->graveyard, dir);
	cachefiles_io_error(cache, "Mountpoint in cache");
	return -EIO;
	}

	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
	if (IS_ERR(grave)) {
	unlock_rename(cache->graveyard, dir);
	trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
	PTR_ERR(grave),
	cachefiles_trace_lookup_error);

	if (PTR_ERR(grave) == -ENOMEM) {
	_leave(" = -ENOMEM");
	return -ENOMEM;
	}

	cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
	return -EIO;
	}

	if (d_is_positive(grave)) {
	unlock_rename(cache->graveyard, dir);
	dput(grave);
	grave = NULL;
	cond_resched();
	goto try_again;
	}

	if (d_mountpoint(grave)) {
	unlock_rename(cache->graveyard, dir);
	dput(grave);
	cachefiles_io_error(cache, "Mountpoint in graveyard");
	return -EIO;
	}

	/* target should not be an ancestor of source */
	if (trap == grave) {
	unlock_rename(cache->graveyard, dir);
	dput(grave);
	cachefiles_io_error(cache, "May not make directory loop");
	return -EIO;
	}

	/* attempt the rename */
	path.mnt = cache->mnt;
	path.dentry = dir;
	path_to_graveyard.mnt = cache->mnt;
	path_to_graveyard.dentry = cache->graveyard;
	ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
	if (ret < 0) {
	cachefiles_io_error(cache, "Rename security error %d", ret);
	} else {
	struct renamedata rd = {
	.old_mnt_idmap = &nop_mnt_idmap,
	.old_dir = d_inode(dir),
	.old_dentry = rep,
	.new_mnt_idmap = &nop_mnt_idmap,
	.new_dir = d_inode(cache->graveyard),
	.new_dentry = grave,
	};
	trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
	ret = cachefiles_inject_read_error();
	if (ret == 0)
	ret = vfs_rename(&rd);
	if (ret != 0)
	trace_cachefiles_vfs_error(object, d_inode(dir), ret,
	cachefiles_trace_rename_error);
	if (ret != 0 && ret != -ENOMEM)
	cachefiles_io_error(cache,
	"Rename failed with error %d", ret);
	}

	__cachefiles_unmark_inode_in_use(object, d_inode(rep));
	unlock_rename(cache->graveyard, dir);
	dput(grave);
	_leave(" = 0");
	return 0;
	}

	/*
	* Delete a cache file.
	*/
	int cachefiles_delete_object(struct cachefiles_object *object,
	enum fscache_why_object_killed why)
	{
	struct cachefiles_volume *volume = object->volume;
	struct dentry *dentry = object->file->f_path.dentry;
	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
	int ret;

	_enter(",OBJ%x{%pD}", object->debug_id, object->file);

	/* Stop the dentry being negated if it's only pinned by a file struct. */
	dget(dentry);

	inode_lock_nested(d_backing_inode(fan), I_MUTEX_PARENT);
	ret = cachefiles_unlink(volume->cache, object, fan, dentry, why);
	inode_unlock(d_backing_inode(fan));
	dput(dentry);
	return ret;
	}

	/*
	* Create a temporary file and leave it unattached and un-xattr'd until the
	* time comes to discard the object from memory.
	*/
	struct file cachefiles_create_tmpfile(struct cachefiles_object object)
	{
	struct cachefiles_volume *volume = object->volume;
	struct cachefiles_cache *cache = volume->cache;
	const struct cred *saved_cred;
	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
	struct file *file;
	const struct path parentpath = { .mnt = cache->mnt, .dentry = fan };
	uint64_t ni_size;
	long ret;


	cachefiles_begin_secure(cache, &saved_cred);

	ret = cachefiles_inject_write_error();
	if (ret == 0) {
	file = kernel_tmpfile_open(&nop_mnt_idmap, &parentpath,
	S_IFREG \| 0600,
	O_RDWR \| O_LARGEFILE \| O_DIRECT,
	cache->cache_cred);
	ret = PTR_ERR_OR_ZERO(file);
	}
	if (ret) {
	trace_cachefiles_vfs_error(object, d_inode(fan), ret,
	cachefiles_trace_tmpfile_error);
	if (ret == -EIO)
	cachefiles_io_error_obj(object, "Failed to create tmpfile");
	goto err;
	}

	trace_cachefiles_tmpfile(object, file_inode(file));

	/* This is a newly created file with no other possible user */
	if (!cachefiles_mark_inode_in_use(object, file_inode(file)))
	WARN_ON(1);

	ret = cachefiles_ondemand_init_object(object);
	if (ret < 0)
	goto err_unuse;

	ni_size = object->cookie->object_size;
	ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);

	if (ni_size > 0) {
	trace_cachefiles_trunc(object, file_inode(file), 0, ni_size,
	cachefiles_trunc_expand_tmpfile);
	ret = cachefiles_inject_write_error();
	if (ret == 0)
	ret = vfs_truncate(&file->f_path, ni_size);
	if (ret < 0) {
	trace_cachefiles_vfs_error(
	object, file_inode(file), ret,
	cachefiles_trace_trunc_error);
	goto err_unuse;
	}
	}

	ret = -EINVAL;
	if (unlikely(!file->f_op->read_iter) \|\|
	unlikely(!file->f_op->write_iter)) {
	fput(file);
	pr_notice("Cache does not support read_iter and write_iter\n");
	goto err_unuse;
	}
	out:
	cachefiles_end_secure(cache, saved_cred);
	return file;

	err_unuse:
	cachefiles_do_unmark_inode_in_use(object, file_inode(file));
	fput(file);
	err:
	file = ERR_PTR(ret);
	goto out;
	}

	/*
	* Create a new file.
	*/
	static bool cachefiles_create_file(struct cachefiles_object *object)
	{
	struct file *file;
	int ret;

	ret = cachefiles_has_space(object->volume->cache, 1, 0,
	cachefiles_has_space_for_create);
	if (ret < 0)
	return false;

	file = cachefiles_create_tmpfile(object);
	if (IS_ERR(file))
	return false;

	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
	set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
	_debug("create -> %pD{ino=%lu}", file, file_inode(file)->i_ino);
	object->file = file;
	return true;
	}

	/*
	* Open an existing file, checking its attributes and replacing it if it is
	* stale.
	*/
	static bool cachefiles_open_file(struct cachefiles_object *object,
	struct dentry *dentry)
	{
	struct cachefiles_cache *cache = object->volume->cache;
	struct file *file;
	struct path path;
	int ret;

	_enter("%pd", dentry);

	if (!cachefiles_mark_inode_in_use(object, d_inode(dentry))) {
	pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
	dentry, d_inode(dentry)->i_ino);
	return false;
	}

	/* We need to open a file interface onto a data file now as we can't do
	* it on demand because writeback called from do_exit() sees
	* current->fs == NULL - which breaks d_path() called from ext4 open.
	*/
	path.mnt = cache->mnt;
	path.dentry = dentry;
	file = kernel_file_open(&path, O_RDWR \| O_LARGEFILE \| O_DIRECT, cache->cache_cred);
	if (IS_ERR(file)) {
	trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
	PTR_ERR(file),
	cachefiles_trace_open_error);
	goto error;
	}

	if (unlikely(!file->f_op->read_iter) \|\|
	unlikely(!file->f_op->write_iter)) {
	pr_notice("Cache does not support read_iter and write_iter\n");
	goto error_fput;
	}
	_debug("file -> %pd positive", dentry);

	ret = cachefiles_ondemand_init_object(object);
	if (ret < 0)
	goto error_fput;

	ret = cachefiles_check_auxdata(object, file);
	if (ret < 0)
	goto check_failed;

	clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &object->cookie->flags);

	object->file = file;

	/* Always update the atime on an object we've just looked up (this is
	* used to keep track of culling, and atimes are only updated by read,
	* write and readdir but not lookup or open).
	*/
	touch_atime(&file->f_path);
	return true;

	check_failed:
	fscache_cookie_lookup_negative(object->cookie);
	cachefiles_unmark_inode_in_use(object, file);
	fput(file);
	if (ret == -ESTALE)
	return cachefiles_create_file(object);
	return false;

	error_fput:
	fput(file);
	error:
	cachefiles_do_unmark_inode_in_use(object, d_inode(dentry));
	return false;
	}

	/*
	* walk from the parent object to the child object through the backing
	* filesystem, creating directories as we go
	*/
	bool cachefiles_look_up_object(struct cachefiles_object *object)
	{
	struct cachefiles_volume *volume = object->volume;
	struct dentry dentry, fan = volume->fanout[(u8)object->cookie->key_hash];
	int ret;

	_enter("OBJ%x,%s,", object->debug_id, object->d_name);

	/* Look up path "cache/vol/fanout/file". */
	ret = cachefiles_inject_read_error();
	if (ret == 0)
	dentry = lookup_positive_unlocked(object->d_name, fan,
	object->d_name_len);
	else
	dentry = ERR_PTR(ret);
	trace_cachefiles_lookup(object, fan, dentry);
	if (IS_ERR(dentry)) {
	if (dentry == ERR_PTR(-ENOENT))
	goto new_file;
	if (dentry == ERR_PTR(-EIO))
	cachefiles_io_error_obj(object, "Lookup failed");
	return false;
	}

	if (!d_is_reg(dentry)) {
	pr_err("%pd is not a file\n", dentry);
	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
	ret = cachefiles_bury_object(volume->cache, object, fan, dentry,
	FSCACHE_OBJECT_IS_WEIRD);
	dput(dentry);
	if (ret < 0)
	return false;
	goto new_file;
	}

	ret = cachefiles_open_file(object, dentry);
	dput(dentry);
	if (!ret)
	return false;

	_leave(" = t [%lu]", file_inode(object->file)->i_ino);
	return true;

	new_file:
	fscache_cookie_lookup_negative(object->cookie);
	return cachefiles_create_file(object);
	}

	/*
	* Attempt to link a temporary file into its rightful place in the cache.
	*/
	bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
	struct cachefiles_object *object)
	{
	struct cachefiles_volume *volume = object->volume;
	struct dentry dentry, fan = volume->fanout[(u8)object->cookie->key_hash];
	bool success = false;
	int ret;

	_enter(",%pD", object->file);

	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
	ret = cachefiles_inject_read_error();
	if (ret == 0)
	dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
	else
	dentry = ERR_PTR(ret);
	if (IS_ERR(dentry)) {
	trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
	cachefiles_trace_lookup_error);
	_debug("lookup fail %ld", PTR_ERR(dentry));
	goto out_unlock;
	}

	if (!d_is_negative(dentry)) {
	ret = cachefiles_unlink(volume->cache, object, fan, dentry,
	FSCACHE_OBJECT_IS_STALE);
	if (ret < 0)
	goto out_dput;

	dput(dentry);
	ret = cachefiles_inject_read_error();
	if (ret == 0)
	dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
	else
	dentry = ERR_PTR(ret);
	if (IS_ERR(dentry)) {
	trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
	cachefiles_trace_lookup_error);
	_debug("lookup fail %ld", PTR_ERR(dentry));
	goto out_unlock;
	}
	}

	ret = cachefiles_inject_read_error();
	if (ret == 0)
	ret = vfs_link(object->file->f_path.dentry, &nop_mnt_idmap,
	d_inode(fan), dentry, NULL);
	if (ret < 0) {
	trace_cachefiles_vfs_error(object, d_inode(fan), ret,
	cachefiles_trace_link_error);
	_debug("link fail %d", ret);
	} else {
	trace_cachefiles_link(object, file_inode(object->file));
	spin_lock(&object->lock);
	/* TODO: Do we want to switch the file pointer to the new dentry? */
	clear_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
	spin_unlock(&object->lock);
	success = true;
	}

	out_dput:
	dput(dentry);
	out_unlock:
	inode_unlock(d_inode(fan));
	_leave(" = %u", success);
	return success;
	}

	/*
	* Look up an inode to be checked or culled. Return -EBUSY if the inode is
	* marked in use.
	*/
	static struct dentry cachefiles_lookup_for_cull(struct cachefiles_cache cache,
	struct dentry *dir,
	char *filename)
	{
	struct dentry *victim;
	int ret = -ENOENT;

	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

	victim = lookup_one_len(filename, dir, strlen(filename));
	if (IS_ERR(victim))
	goto lookup_error;
	if (d_is_negative(victim))
	goto lookup_put;
	if (d_inode(victim)->i_flags & S_KERNEL_FILE)
	goto lookup_busy;
	return victim;

	lookup_busy:
	ret = -EBUSY;
	lookup_put:
	inode_unlock(d_inode(dir));
	dput(victim);
	return ERR_PTR(ret);

	lookup_error:
	inode_unlock(d_inode(dir));
	ret = PTR_ERR(victim);
	if (ret == -ENOENT)
	return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */

	if (ret == -EIO) {
	cachefiles_io_error(cache, "Lookup failed");
	} else if (ret != -ENOMEM) {
	pr_err("Internal error: %d\n", ret);
	ret = -EIO;
	}

	return ERR_PTR(ret);
	}

	/*
	* Cull an object if it's not in use
	* - called only by cache manager daemon
	*/
	int cachefiles_cull(struct cachefiles_cache cache, struct dentry dir,
	char *filename)
	{
	struct dentry *victim;
	struct inode *inode;
	int ret;

	_enter(",%pd/,%s", dir, filename);

	victim = cachefiles_lookup_for_cull(cache, dir, filename);
	if (IS_ERR(victim))
	return PTR_ERR(victim);

	/* check to see if someone is using this object */
	inode = d_inode(victim);
	inode_lock(inode);
	if (inode->i_flags & S_KERNEL_FILE) {
	ret = -EBUSY;
	} else {
	/* Stop the cache from picking it back up */
	inode->i_flags \|= S_KERNEL_FILE;
	ret = 0;
	}
	inode_unlock(inode);
	if (ret < 0)
	goto error_unlock;

	ret = cachefiles_bury_object(cache, NULL, dir, victim,
	FSCACHE_OBJECT_WAS_CULLED);
	if (ret < 0)
	goto error;

	fscache_count_culled();
	dput(victim);
	_leave(" = 0");
	return 0;

	error_unlock:
	inode_unlock(d_inode(dir));
	error:
	dput(victim);
	if (ret == -ENOENT)
	return -ESTALE; /* Probably got retired by the netfs */

	if (ret != -ENOMEM) {
	pr_err("Internal error: %d\n", ret);
	ret = -EIO;
	}

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

	/*
	* Find out if an object is in use or not
	* - called only by cache manager daemon
	* - returns -EBUSY or 0 to indicate whether an object is in use or not
	*/
	int cachefiles_check_in_use(struct cachefiles_cache cache, struct dentry dir,
	char *filename)
	{
	struct dentry *victim;
	int ret = 0;

	victim = cachefiles_lookup_for_cull(cache, dir, filename);
	if (IS_ERR(victim))
	return PTR_ERR(victim);

	inode_unlock(d_inode(dir));
	dput(victim);
	return ret;
	}