Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 863 insertions, 0 deletions

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
new file mode 100644
index 0000000000..7bf7a5fcc0
--- /dev/null
+++ b/fs/cachefiles/namei.c
@@ -0,0 +1,863 @@
+// 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);
+
+	/* 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,
+				d_backing_inode(dentry), 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);
+	dput(dentry);
+	return true;
+
+check_failed:
+	fscache_cookie_lookup_negative(object->cookie);
+	cachefiles_unmark_inode_in_use(object, file);
+	fput(file);
+	dput(dentry);
+	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));
+	dput(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;
+	}
+
+	if (!cachefiles_open_file(object, dentry))
+		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)) {
+		if (d_backing_inode(dentry) == file_inode(object->file)) {
+			success = true;
+			goto out_dput;
+		}
+
+		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;
+}