/* 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>
#include <linux/slab.h>
#include "internal.h"

#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;

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

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

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

/*
 * 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);
}

/*
 * 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,
               fscache_object_states[object->fscache.state],
               dentry);

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

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

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

        _enter(",%p", object);

try_again:
        write_lock(&cache->active_lock);

        if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
                printk(KERN_ERR "CacheFiles: Error: Object already active\n");
                cachefiles_printk_object(object, NULL);
                BUG();
        }

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

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

        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 */
                if (work_pending(&xobject->fscache.work)) {
                        _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
                 * is done, or the fscache_object is congested */
                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;

                        requeue = fscache_object_sleep_till_congested(&timeout);
                } 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) {
                        printk(KERN_ERR "\n");
                        printk(KERN_ERR "CacheFiles: Error: Overlong"
                               " wait for old active object to go away\n");
                        cachefiles_printk_object(object, xobject);
                        goto requeue;
                }
        }

        ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));

        cache->cache.ops->put_object(&xobject->fscache);
        goto try_again;

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

/*
 * 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,
                                  struct dentry *rep,
                                  bool preemptive)
{
        struct dentry *grave, *trap;
        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);

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

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

                if (preemptive)
                        cachefiles_mark_object_buried(cache, rep);

                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 */
        ret = vfs_rename(dir->d_inode, rep, cache->graveyard->d_inode, grave);
        if (ret != 0 && ret != -ENOMEM)
                cachefiles_io_error(cache, "Rename failed with error %d", ret);

        if (preemptive)
                cachefiles_mark_object_buried(cache, rep);

        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;

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

        ASSERT(object->dentry);
        ASSERT(object->dentry->d_inode);
        ASSERT(object->dentry->d_parent);

        dir = dget_parent(object->dentry);

        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);

        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");
                mutex_unlock(&dir->d_inode->i_mutex);
                ret = 0;
        } 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;
                }
        }

        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;
        unsigned long start;
        const char *name;
        int ret, nlen;

        _enter("OBJ%x{%p},OBJ%x,%s,",
               parent->fscache.debug_id, parent->dentry,
               object->fscache.debug_id, key);

        cache = container_of(parent->fscache.cache,
                             struct cachefiles_cache, cache);

        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);

        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);

        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;

                        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;

                        start = jiffies;
                        ret = vfs_create(dir->d_inode, next, S_IFREG, NULL);
                        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;

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

                        if (ret < 0)
                                goto delete_error;

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

        /* note that we're now using this object */
        ret = cachefiles_mark_object_active(cache, object);

        mutex_unlock(&dir->d_inode->i_mutex);
        dput(dir);
        dir = NULL;

        if (ret == -ETIMEDOUT)
                goto mark_active_timed_out;

        _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) */
                touch_atime(cache->mnt, next);
        }

        /* 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;

mark_active_timed_out:
        _debug("mark active timed out");
        goto release_dentry;

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);
release_dentry:
        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;
        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");

                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;
        if (!subdir->d_inode->i_op ||
            !subdir->d_inode->i_op->setxattr ||
            !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 */
        mutex_lock_nested(&dir->d_inode->i_mutex, 1);

        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");

        ret = cachefiles_bury_object(cache, dir, victim, false);
        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;
}