// 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 */

retry:
        ret = cachefiles_inject_read_error();
        if (ret == 0)
                subdir = start_creating(&nop_mnt_idmap, dir, &QSTR(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) {
                        subdir = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700, NULL);
                } else {
                        end_creating(subdir);
                        subdir = ERR_PTR(ret);
                }
                if (IS_ERR(subdir)) {
                        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) || d_is_negative(subdir))) {
                        end_creating(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));
        end_creating_keep(subdir);

        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:
        end_creating(subdir);
        pr_err("mkdir %s failed with error %d\n", dirname, ret);
        return ERR_PTR(ret);

lookup_error:
        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
 * On entry dir must be locked.  It will be unlocked on exit.
 * On entry there must be at least 2 refs on rep, one will be dropped on exit.
 */
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) {
                end_removing(rep);
                _leave(" = -ESTALE");
                return -ESTALE;
        }

        /* non-directories can just be unlinked */
        if (!d_is_dir(rep)) {
                ret = cachefiles_unlink(cache, object, dir, rep, why);
                end_removing(rep);

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

        /* directories have to be moved to the graveyard */
        _debug("move stale object to graveyard");
        end_removing(rep);

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(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
        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 = {
                        .mnt_idmap      = &nop_mnt_idmap,
                        .old_parent     = dir,
                        .old_dentry     = rep,
                        .new_parent     = 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);

        dentry = start_removing_dentry(fan, dentry);
        if (IS_ERR(dentry))
                ret = PTR_ERR(dentry);
        else
                ret = cachefiles_unlink(volume->cache, object, fan, dentry, why);
        end_removing(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_one_positive_unlocked(&nop_mnt_idmap,
                                                      &QSTR(object->d_name), fan);
        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);
                struct dentry *de = start_removing_dentry(fan, dentry);
                if (IS_ERR(de))
                        ret = PTR_ERR(de);
                else
                        ret = cachefiles_bury_object(volume->cache, object,
                                                     fan, de,
                                                     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);

        ret = cachefiles_inject_read_error();
        if (ret == 0)
                dentry = start_creating(&nop_mnt_idmap, fan, &QSTR(object->d_name));
        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;
        }

        /*
         * This loop will only execute more than once if some other thread
         * races to create the object we are trying to create.
         */
        while (!d_is_negative(dentry)) {
                ret = cachefiles_unlink(volume->cache, object, fan, dentry,
                                        FSCACHE_OBJECT_IS_STALE);
                if (ret < 0)
                        goto out_end;

                end_creating(dentry);

                ret = cachefiles_inject_read_error();
                if (ret == 0)
                        dentry = start_creating(&nop_mnt_idmap, fan,
                                                &QSTR(object->d_name));
                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;
                }
        }

        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_end:
        end_creating(dentry);
out:
        _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;

        victim = start_removing(&nop_mnt_idmap, dir, &QSTR(filename));

        if (IS_ERR(victim))
                goto lookup_error;
        if (d_inode(victim)->i_flags & S_KERNEL_FILE)
                goto lookup_busy;
        return victim;

lookup_busy:
        ret = -EBUSY;
        end_removing(victim);
        return ERR_PTR(ret);

lookup_error:
        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);
        dput(victim);
        if (ret < 0)
                goto error;

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

error_unlock:
        end_removing(victim);
error:
        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;
}