namei.c 24.4 KB
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/* CacheFiles path walking and related routines
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/quotaops.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/security.h>
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#include <linux/slab.h>
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#include "internal.h"

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#define CACHEFILES_KEYBUF_SIZE 512

/*
 * dump debugging info about an object
 */
static noinline
void __cachefiles_printk_object(struct cachefiles_object *object,
				const char *prefix,
				u8 *keybuf)
{
	struct fscache_cookie *cookie;
	unsigned keylen, loop;

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	pr_err("%sobject: OBJ%x\n", prefix, object->fscache.debug_id);
	pr_err("%sobjstate=%s fl=%lx wbusy=%x ev=%lx[%lx]\n",
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	       prefix, object->fscache.state->name,
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	       object->fscache.flags, work_busy(&object->fscache.work),
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	       object->fscache.events, object->fscache.event_mask);
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	pr_err("%sops=%u inp=%u exc=%u\n",
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	       prefix, object->fscache.n_ops, object->fscache.n_in_progress,
	       object->fscache.n_exclusive);
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	pr_err("%sparent=%p\n",
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	       prefix, object->fscache.parent);

	spin_lock(&object->fscache.lock);
	cookie = object->fscache.cookie;
	if (cookie) {
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		pr_err("%scookie=%p [pr=%p nd=%p fl=%lx]\n",
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		       prefix,
		       object->fscache.cookie,
		       object->fscache.cookie->parent,
		       object->fscache.cookie->netfs_data,
		       object->fscache.cookie->flags);
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		if (keybuf && cookie->def)
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			keylen = cookie->def->get_key(cookie->netfs_data, keybuf,
						      CACHEFILES_KEYBUF_SIZE);
		else
			keylen = 0;
	} else {
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		pr_err("%scookie=NULL\n", prefix);
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		keylen = 0;
	}
	spin_unlock(&object->fscache.lock);

	if (keylen) {
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		pr_err("%skey=[%u] '", prefix, keylen);
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		for (loop = 0; loop < keylen; loop++)
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			pr_cont("%02x", keybuf[loop]);
		pr_cont("'\n");
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	}
}

/*
 * dump debugging info about a pair of objects
 */
static noinline void cachefiles_printk_object(struct cachefiles_object *object,
					      struct cachefiles_object *xobject)
{
	u8 *keybuf;

	keybuf = kmalloc(CACHEFILES_KEYBUF_SIZE, GFP_NOIO);
	if (object)
		__cachefiles_printk_object(object, "", keybuf);
	if (xobject)
		__cachefiles_printk_object(xobject, "x", keybuf);
	kfree(keybuf);
}

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/*
 * mark the owner of a dentry, if there is one, to indicate that that dentry
 * has been preemptively deleted
 * - the caller must hold the i_mutex on the dentry's parent as required to
 *   call vfs_unlink(), vfs_rmdir() or vfs_rename()
 */
static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,
					  struct dentry *dentry)
{
	struct cachefiles_object *object;
	struct rb_node *p;

	_enter(",'%*.*s'",
	       dentry->d_name.len, dentry->d_name.len, dentry->d_name.name);

	write_lock(&cache->active_lock);

	p = cache->active_nodes.rb_node;
	while (p) {
		object = rb_entry(p, struct cachefiles_object, active_node);
		if (object->dentry > dentry)
			p = p->rb_left;
		else if (object->dentry < dentry)
			p = p->rb_right;
		else
			goto found_dentry;
	}

	write_unlock(&cache->active_lock);
	_leave(" [no owner]");
	return;

	/* found the dentry for  */
found_dentry:
	kdebug("preemptive burial: OBJ%x [%s] %p",
	       object->fscache.debug_id,
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	       object->fscache.state->name,
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	       dentry);

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	if (fscache_object_is_live(&object->fscache)) {
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		pr_err("\n");
		pr_err("CacheFiles: Error: Can't preemptively bury live object\n");
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		cachefiles_printk_object(object, NULL);
	} else if (test_and_set_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {
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		pr_err("CacheFiles: Error: Object already preemptively buried\n");
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	}

	write_unlock(&cache->active_lock);
	_leave(" [owner marked]");
}

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/*
 * record the fact that an object is now active
 */
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static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
					 struct cachefiles_object *object)
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{
	struct cachefiles_object *xobject;
	struct rb_node **_p, *_parent = NULL;
	struct dentry *dentry;

	_enter(",%p", object);

try_again:
	write_lock(&cache->active_lock);

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	if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
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		pr_err("CacheFiles: Error: Object already active\n");
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		cachefiles_printk_object(object, NULL);
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		BUG();
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	}
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	dentry = object->dentry;
	_p = &cache->active_nodes.rb_node;
	while (*_p) {
		_parent = *_p;
		xobject = rb_entry(_parent,
				   struct cachefiles_object, active_node);

		ASSERT(xobject != object);

		if (xobject->dentry > dentry)
			_p = &(*_p)->rb_left;
		else if (xobject->dentry < dentry)
			_p = &(*_p)->rb_right;
		else
			goto wait_for_old_object;
	}

	rb_link_node(&object->active_node, _parent, _p);
	rb_insert_color(&object->active_node, &cache->active_nodes);

	write_unlock(&cache->active_lock);
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	_leave(" = 0");
	return 0;
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	/* an old object from a previous incarnation is hogging the slot - we
	 * need to wait for it to be destroyed */
wait_for_old_object:
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	if (fscache_object_is_live(&object->fscache)) {
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		pr_err("\n");
		pr_err("CacheFiles: Error: Unexpected object collision\n");
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		cachefiles_printk_object(object, xobject);
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		BUG();
	}
	atomic_inc(&xobject->usage);
	write_unlock(&cache->active_lock);

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	if (test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
		wait_queue_head_t *wq;

		signed long timeout = 60 * HZ;
		wait_queue_t wait;
		bool requeue;

		/* if the object we're waiting for is queued for processing,
		 * then just put ourselves on the queue behind it */
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		if (work_pending(&xobject->fscache.work)) {
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			_debug("queue OBJ%x behind OBJ%x immediately",
			       object->fscache.debug_id,
			       xobject->fscache.debug_id);
			goto requeue;
		}

		/* otherwise we sleep until either the object we're waiting for
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		 * is done, or the fscache_object is congested */
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		wq = bit_waitqueue(&xobject->flags, CACHEFILES_OBJECT_ACTIVE);
		init_wait(&wait);
		requeue = false;
		do {
			prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
			if (!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags))
				break;
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			requeue = fscache_object_sleep_till_congested(&timeout);
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		} while (timeout > 0 && !requeue);
		finish_wait(wq, &wait);

		if (requeue &&
		    test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
			_debug("queue OBJ%x behind OBJ%x after wait",
			       object->fscache.debug_id,
			       xobject->fscache.debug_id);
			goto requeue;
		}

		if (timeout <= 0) {
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			pr_err("\n");
			pr_err("CacheFiles: Error: Overlong wait for old active object to go away\n");
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			cachefiles_printk_object(object, xobject);
			goto requeue;
		}
	}

	ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));
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	cache->cache.ops->put_object(&xobject->fscache);
	goto try_again;
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requeue:
	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
	cache->cache.ops->put_object(&xobject->fscache);
	_leave(" = -ETIMEDOUT");
	return -ETIMEDOUT;
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}

/*
 * delete an object representation from the cache
 * - file backed objects are unlinked
 * - directory backed objects are stuffed into the graveyard for userspace to
 *   delete
 * - unlocks the directory mutex
 */
static int cachefiles_bury_object(struct cachefiles_cache *cache,
				  struct dentry *dir,
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				  struct dentry *rep,
				  bool preemptive)
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{
	struct dentry *grave, *trap;
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	struct path path, path_to_graveyard;
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	char nbuffer[8 + 8 + 1];
	int ret;

	_enter(",'%*.*s','%*.*s'",
	       dir->d_name.len, dir->d_name.len, dir->d_name.name,
	       rep->d_name.len, rep->d_name.len, rep->d_name.name);

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	_debug("remove %p from %p", rep, dir);

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	/* non-directories can just be unlinked */
	if (!S_ISDIR(rep->d_inode->i_mode)) {
		_debug("unlink stale object");

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		path.mnt = cache->mnt;
		path.dentry = dir;
		ret = security_path_unlink(&path, rep);
		if (ret < 0) {
			cachefiles_io_error(cache, "Unlink security error");
		} else {
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			ret = vfs_unlink(dir->d_inode, rep, NULL);
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			if (preemptive)
				cachefiles_mark_object_buried(cache, rep);
		}
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		mutex_unlock(&dir->d_inode->i_mutex);

		if (ret == -EIO)
			cachefiles_io_error(cache, "Unlink failed");

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

	/* directories have to be moved to the graveyard */
	_debug("move stale object to graveyard");
	mutex_unlock(&dir->d_inode->i_mutex);

try_again:
	/* first step is to make up a grave dentry in the graveyard */
	sprintf(nbuffer, "%08x%08x",
		(uint32_t) get_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) {
		/* the entry was probably culled when we dropped the parent dir
		 * lock */
		unlock_rename(cache->graveyard, dir);
		_leave(" = 0 [culled?]");
		return 0;
	}

	if (!S_ISDIR(cache->graveyard->d_inode->i_mode)) {
		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);

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

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

	if (grave->d_inode) {
		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 */
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	path.mnt = cache->mnt;
	path.dentry = dir;
	path_to_graveyard.mnt = cache->mnt;
	path_to_graveyard.dentry = cache->graveyard;
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	ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
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	if (ret < 0) {
		cachefiles_io_error(cache, "Rename security error %d", ret);
	} else {
		ret = vfs_rename(dir->d_inode, rep,
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				 cache->graveyard->d_inode, grave, NULL, 0);
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		if (ret != 0 && ret != -ENOMEM)
			cachefiles_io_error(cache,
					    "Rename failed with error %d", ret);
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		if (preemptive)
			cachefiles_mark_object_buried(cache, rep);
	}
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	unlock_rename(cache->graveyard, dir);
	dput(grave);
	_leave(" = 0");
	return 0;
}

/*
 * delete an object representation from the cache
 */
int cachefiles_delete_object(struct cachefiles_cache *cache,
			     struct cachefiles_object *object)
{
	struct dentry *dir;
	int ret;

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	_enter(",OBJ%x{%p}", object->fscache.debug_id, object->dentry);
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	ASSERT(object->dentry);
	ASSERT(object->dentry->d_inode);
	ASSERT(object->dentry->d_parent);

	dir = dget_parent(object->dentry);

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	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
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	if (test_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {
		/* object allocation for the same key preemptively deleted this
		 * object's file so that it could create its own file */
		_debug("object preemptively buried");
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		mutex_unlock(&dir->d_inode->i_mutex);
		ret = 0;
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	} else {
		/* we need to check that our parent is _still_ our parent - it
		 * may have been renamed */
		if (dir == object->dentry->d_parent) {
			ret = cachefiles_bury_object(cache, dir,
						     object->dentry, false);
		} else {
			/* it got moved, presumably by cachefilesd culling it,
			 * so it's no longer in the key path and we can ignore
			 * it */
			mutex_unlock(&dir->d_inode->i_mutex);
			ret = 0;
		}
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	}
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	dput(dir);
	_leave(" = %d", ret);
	return ret;
}

/*
 * walk from the parent object to the child object through the backing
 * filesystem, creating directories as we go
 */
int cachefiles_walk_to_object(struct cachefiles_object *parent,
			      struct cachefiles_object *object,
			      const char *key,
			      struct cachefiles_xattr *auxdata)
{
	struct cachefiles_cache *cache;
	struct dentry *dir, *next = NULL;
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	struct path path;
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	unsigned long start;
	const char *name;
	int ret, nlen;

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	_enter("OBJ%x{%p},OBJ%x,%s,",
	       parent->fscache.debug_id, parent->dentry,
	       object->fscache.debug_id, key);
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	cache = container_of(parent->fscache.cache,
			     struct cachefiles_cache, cache);
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	path.mnt = cache->mnt;
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	ASSERT(parent->dentry);
	ASSERT(parent->dentry->d_inode);

	if (!(S_ISDIR(parent->dentry->d_inode->i_mode))) {
		// TODO: convert file to dir
		_leave("looking up in none directory");
		return -ENOBUFS;
	}

	dir = dget(parent->dentry);

advance:
	/* attempt to transit the first directory component */
	name = key;
	nlen = strlen(key);

	/* key ends in a double NUL */
	key = key + nlen + 1;
	if (!*key)
		key = NULL;

lookup_again:
	/* search the current directory for the element name */
	_debug("lookup '%s'", name);

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	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
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	start = jiffies;
	next = lookup_one_len(name, dir, nlen);
	cachefiles_hist(cachefiles_lookup_histogram, start);
	if (IS_ERR(next))
		goto lookup_error;

	_debug("next -> %p %s", next, next->d_inode ? "positive" : "negative");

	if (!key)
		object->new = !next->d_inode;

	/* if this element of the path doesn't exist, then the lookup phase
	 * failed, and we can release any readers in the certain knowledge that
	 * there's nothing for them to actually read */
	if (!next->d_inode)
		fscache_object_lookup_negative(&object->fscache);

	/* we need to create the object if it's negative */
	if (key || object->type == FSCACHE_COOKIE_TYPE_INDEX) {
		/* index objects and intervening tree levels must be subdirs */
		if (!next->d_inode) {
			ret = cachefiles_has_space(cache, 1, 0);
			if (ret < 0)
				goto create_error;

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			path.dentry = dir;
			ret = security_path_mkdir(&path, next, 0);
			if (ret < 0)
				goto create_error;
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			start = jiffies;
			ret = vfs_mkdir(dir->d_inode, next, 0);
			cachefiles_hist(cachefiles_mkdir_histogram, start);
			if (ret < 0)
				goto create_error;

			ASSERT(next->d_inode);

			_debug("mkdir -> %p{%p{ino=%lu}}",
			       next, next->d_inode, next->d_inode->i_ino);

		} else if (!S_ISDIR(next->d_inode->i_mode)) {
			kerror("inode %lu is not a directory",
			       next->d_inode->i_ino);
			ret = -ENOBUFS;
			goto error;
		}

	} else {
		/* non-index objects start out life as files */
		if (!next->d_inode) {
			ret = cachefiles_has_space(cache, 1, 0);
			if (ret < 0)
				goto create_error;

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			path.dentry = dir;
			ret = security_path_mknod(&path, next, S_IFREG, 0);
			if (ret < 0)
				goto create_error;
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			start = jiffies;
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			ret = vfs_create(dir->d_inode, next, S_IFREG, true);
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			cachefiles_hist(cachefiles_create_histogram, start);
			if (ret < 0)
				goto create_error;

			ASSERT(next->d_inode);

			_debug("create -> %p{%p{ino=%lu}}",
			       next, next->d_inode, next->d_inode->i_ino);

		} else if (!S_ISDIR(next->d_inode->i_mode) &&
			   !S_ISREG(next->d_inode->i_mode)
			   ) {
			kerror("inode %lu is not a file or directory",
			       next->d_inode->i_ino);
			ret = -ENOBUFS;
			goto error;
		}
	}

	/* process the next component */
	if (key) {
		_debug("advance");
		mutex_unlock(&dir->d_inode->i_mutex);
		dput(dir);
		dir = next;
		next = NULL;
		goto advance;
	}

	/* we've found the object we were looking for */
	object->dentry = next;

	/* if we've found that the terminal object exists, then we need to
	 * check its attributes and delete it if it's out of date */
	if (!object->new) {
		_debug("validate '%*.*s'",
		       next->d_name.len, next->d_name.len, next->d_name.name);

		ret = cachefiles_check_object_xattr(object, auxdata);
		if (ret == -ESTALE) {
			/* delete the object (the deleter drops the directory
			 * mutex) */
			object->dentry = NULL;

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			ret = cachefiles_bury_object(cache, dir, next, true);
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			dput(next);
			next = NULL;

			if (ret < 0)
				goto delete_error;

			_debug("redo lookup");
			goto lookup_again;
		}
	}

	/* note that we're now using this object */
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	ret = cachefiles_mark_object_active(cache, object);
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	mutex_unlock(&dir->d_inode->i_mutex);
	dput(dir);
	dir = NULL;

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	if (ret == -ETIMEDOUT)
		goto mark_active_timed_out;

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	_debug("=== OBTAINED_OBJECT ===");

	if (object->new) {
		/* attach data to a newly constructed terminal object */
		ret = cachefiles_set_object_xattr(object, auxdata);
		if (ret < 0)
			goto check_error;
	} else {
		/* 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) */
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		path.dentry = next;
		touch_atime(&path);
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	}

	/* open a file interface onto a data file */
	if (object->type != FSCACHE_COOKIE_TYPE_INDEX) {
		if (S_ISREG(object->dentry->d_inode->i_mode)) {
			const struct address_space_operations *aops;

			ret = -EPERM;
			aops = object->dentry->d_inode->i_mapping->a_ops;
			if (!aops->bmap)
				goto check_error;

			object->backer = object->dentry;
		} else {
			BUG(); // TODO: open file in data-class subdir
		}
	}

	object->new = 0;
	fscache_obtained_object(&object->fscache);

	_leave(" = 0 [%lu]", object->dentry->d_inode->i_ino);
	return 0;

create_error:
	_debug("create error %d", ret);
	if (ret == -EIO)
		cachefiles_io_error(cache, "Create/mkdir failed");
	goto error;

675 676 677 678
mark_active_timed_out:
	_debug("mark active timed out");
	goto release_dentry;

679 680 681 682 683 684 685
check_error:
	_debug("check error %d", ret);
	write_lock(&cache->active_lock);
	rb_erase(&object->active_node, &cache->active_nodes);
	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
	wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
	write_unlock(&cache->active_lock);
686
release_dentry:
687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719
	dput(object->dentry);
	object->dentry = NULL;
	goto error_out;

delete_error:
	_debug("delete error %d", ret);
	goto error_out2;

lookup_error:
	_debug("lookup error %ld", PTR_ERR(next));
	ret = PTR_ERR(next);
	if (ret == -EIO)
		cachefiles_io_error(cache, "Lookup failed");
	next = NULL;
error:
	mutex_unlock(&dir->d_inode->i_mutex);
	dput(next);
error_out2:
	dput(dir);
error_out:
	_leave(" = error %d", -ret);
	return ret;
}

/*
 * get a subdirectory
 */
struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
					struct dentry *dir,
					const char *dirname)
{
	struct dentry *subdir;
	unsigned long start;
720
	struct path path;
721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747
	int ret;

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

	/* search the current directory for the element name */
	mutex_lock(&dir->d_inode->i_mutex);

	start = jiffies;
	subdir = lookup_one_len(dirname, dir, strlen(dirname));
	cachefiles_hist(cachefiles_lookup_histogram, start);
	if (IS_ERR(subdir)) {
		if (PTR_ERR(subdir) == -ENOMEM)
			goto nomem_d_alloc;
		goto lookup_error;
	}

	_debug("subdir -> %p %s",
	       subdir, subdir->d_inode ? "positive" : "negative");

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

		_debug("attempt mkdir");

748 749 750 751 752
		path.mnt = cache->mnt;
		path.dentry = dir;
		ret = security_path_mkdir(&path, subdir, 0700);
		if (ret < 0)
			goto mkdir_error;
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776
		ret = vfs_mkdir(dir->d_inode, subdir, 0700);
		if (ret < 0)
			goto mkdir_error;

		ASSERT(subdir->d_inode);

		_debug("mkdir -> %p{%p{ino=%lu}}",
		       subdir,
		       subdir->d_inode,
		       subdir->d_inode->i_ino);
	}

	mutex_unlock(&dir->d_inode->i_mutex);

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

	if (!S_ISDIR(subdir->d_inode->i_mode)) {
		kerror("%s is not a directory", dirname);
		ret = -EIO;
		goto check_error;
	}

	ret = -EPERM;
777
	if (!subdir->d_inode->i_op->setxattr ||
778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832
	    !subdir->d_inode->i_op->getxattr ||
	    !subdir->d_inode->i_op->lookup ||
	    !subdir->d_inode->i_op->mkdir ||
	    !subdir->d_inode->i_op->create ||
	    !subdir->d_inode->i_op->rename ||
	    !subdir->d_inode->i_op->rmdir ||
	    !subdir->d_inode->i_op->unlink)
		goto check_error;

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

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

mkdir_error:
	mutex_unlock(&dir->d_inode->i_mutex);
	dput(subdir);
	kerror("mkdir %s failed with error %d", dirname, ret);
	return ERR_PTR(ret);

lookup_error:
	mutex_unlock(&dir->d_inode->i_mutex);
	ret = PTR_ERR(subdir);
	kerror("Lookup %s failed with error %d", dirname, ret);
	return ERR_PTR(ret);

nomem_d_alloc:
	mutex_unlock(&dir->d_inode->i_mutex);
	_leave(" = -ENOMEM");
	return ERR_PTR(-ENOMEM);
}

/*
 * find out if an object is in use or not
 * - if finds object and it's not in use:
 *   - returns a pointer to the object and a reference on it
 *   - returns with the directory locked
 */
static struct dentry *cachefiles_check_active(struct cachefiles_cache *cache,
					      struct dentry *dir,
					      char *filename)
{
	struct cachefiles_object *object;
	struct rb_node *_n;
	struct dentry *victim;
	unsigned long start;
	int ret;

	//_enter(",%*.*s/,%s",
	//       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);

	/* look up the victim */
833
	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933

	start = jiffies;
	victim = lookup_one_len(filename, dir, strlen(filename));
	cachefiles_hist(cachefiles_lookup_histogram, start);
	if (IS_ERR(victim))
		goto lookup_error;

	//_debug("victim -> %p %s",
	//       victim, victim->d_inode ? "positive" : "negative");

	/* if the object is no longer there then we probably retired the object
	 * at the netfs's request whilst the cull was in progress
	 */
	if (!victim->d_inode) {
		mutex_unlock(&dir->d_inode->i_mutex);
		dput(victim);
		_leave(" = -ENOENT [absent]");
		return ERR_PTR(-ENOENT);
	}

	/* check to see if we're using this object */
	read_lock(&cache->active_lock);

	_n = cache->active_nodes.rb_node;

	while (_n) {
		object = rb_entry(_n, struct cachefiles_object, active_node);

		if (object->dentry > victim)
			_n = _n->rb_left;
		else if (object->dentry < victim)
			_n = _n->rb_right;
		else
			goto object_in_use;
	}

	read_unlock(&cache->active_lock);

	//_leave(" = %p", victim);
	return victim;

object_in_use:
	read_unlock(&cache->active_lock);
	mutex_unlock(&dir->d_inode->i_mutex);
	dput(victim);
	//_leave(" = -EBUSY [in use]");
	return ERR_PTR(-EBUSY);

lookup_error:
	mutex_unlock(&dir->d_inode->i_mutex);
	ret = PTR_ERR(victim);
	if (ret == -ENOENT) {
		/* file or dir now absent - probably retired by netfs */
		_leave(" = -ESTALE [absent]");
		return ERR_PTR(-ESTALE);
	}

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

	_leave(" = %d", ret);
	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;
	int ret;

	_enter(",%*.*s/,%s",
	       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);

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

	_debug("victim -> %p %s",
	       victim, victim->d_inode ? "positive" : "negative");

	/* okay... the victim is not being used so we can cull it
	 * - start by marking it as stale
	 */
	_debug("victim is cullable");

	ret = cachefiles_remove_object_xattr(cache, victim);
	if (ret < 0)
		goto error_unlock;

	/*  actually remove the victim (drops the dir mutex) */
	_debug("bury");

934
	ret = cachefiles_bury_object(cache, dir, victim, false);
935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982
	if (ret < 0)
		goto error;

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

error_unlock:
	mutex_unlock(&dir->d_inode->i_mutex);
error:
	dput(victim);
	if (ret == -ENOENT) {
		/* file or dir now absent - probably retired by netfs */
		_leave(" = -ESTALE [absent]");
		return -ESTALE;
	}

	if (ret != -ENOMEM) {
		kerror("Internal error: %d", 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;

	//_enter(",%*.*s/,%s",
	//       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);

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

	mutex_unlock(&dir->d_inode->i_mutex);
	dput(victim);
	//_leave(" = 0");
	return 0;
}