path: root/fs/fscache/cookie.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* netfs cookie management
 *
 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * See Documentation/filesystems/caching/netfs-api.rst for more information on
 * the netfs API.
 */

#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include <linux/slab.h>
#include "internal.h"

struct kmem_cache *fscache_cookie_jar;

static atomic_t fscache_object_debug_id = ATOMIC_INIT(0);

#define fscache_cookie_hash_shift 15
static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
static LIST_HEAD(fscache_cookies);
static DEFINE_RWLOCK(fscache_cookies_lock);

static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie,
					    loff_t object_size);
static int fscache_alloc_object(struct fscache_cache *cache,
				struct fscache_cookie *cookie);
static int fscache_attach_object(struct fscache_cookie *cookie,
				 struct fscache_object *object);

static void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
{
	struct fscache_object *object;
	struct hlist_node *o;
	const u8 *k;
	unsigned loop;

	pr_err("%c-cookie c=%08x [p=%08x fl=%lx nc=%u na=%u]\n",
	       prefix,
	       cookie->debug_id,
	       cookie->parent ? cookie->parent->debug_id : 0,
	       cookie->flags,
	       atomic_read(&cookie->n_children),
	       atomic_read(&cookie->n_active));
	pr_err("%c-cookie d=%p{%s} n=%p\n",
	       prefix,
	       cookie->def,
	       cookie->def ? cookie->def->name : "?",
	       cookie->netfs_data);

	o = READ_ONCE(cookie->backing_objects.first);
	if (o) {
		object = hlist_entry(o, struct fscache_object, cookie_link);
		pr_err("%c-cookie o=%u\n", prefix, object->debug_id);
	}

	pr_err("%c-key=[%u] '", prefix, cookie->key_len);
	k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
		cookie->inline_key : cookie->key;
	for (loop = 0; loop < cookie->key_len; loop++)
		pr_cont("%02x", k[loop]);
	pr_cont("'\n");
}

void fscache_free_cookie(struct fscache_cookie *cookie)
{
	if (cookie) {
		BUG_ON(!hlist_empty(&cookie->backing_objects));
		write_lock(&fscache_cookies_lock);
		list_del(&cookie->proc_link);
		write_unlock(&fscache_cookies_lock);
		if (cookie->aux_len > sizeof(cookie->inline_aux))
			kfree(cookie->aux);
		if (cookie->key_len > sizeof(cookie->inline_key))
			kfree(cookie->key);
		kmem_cache_free(fscache_cookie_jar, cookie);
	}
}

/*
 * Set the index key in a cookie.  The cookie struct has space for a 16-byte
 * key plus length and hash, but if that's not big enough, it's instead a
 * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then
 * the key data.
 */
static int fscache_set_key(struct fscache_cookie *cookie,
			   const void *index_key, size_t index_key_len)
{
	unsigned long long h;
	u32 *buf;
	int bufs;
	int i;

	bufs = DIV_ROUND_UP(index_key_len, sizeof(*buf));

	if (index_key_len > sizeof(cookie->inline_key)) {
		buf = kcalloc(bufs, sizeof(*buf), GFP_KERNEL);
		if (!buf)
			return -ENOMEM;
		cookie->key = buf;
	} else {
		buf = (u32 *)cookie->inline_key;
	}

	memcpy(buf, index_key, index_key_len);

	/* Calculate a hash and combine this with the length in the first word
	 * or first half word
	 */
	h = (unsigned long)cookie->parent;
	h += index_key_len + cookie->type;

	for (i = 0; i < bufs; i++)
		h += buf[i];

	cookie->key_hash = h ^ (h >> 32);
	return 0;
}

static long fscache_compare_cookie(const struct fscache_cookie *a,
				   const struct fscache_cookie *b)
{
	const void *ka, *kb;

	if (a->key_hash != b->key_hash)
		return (long)a->key_hash - (long)b->key_hash;
	if (a->parent != b->parent)
		return (long)a->parent - (long)b->parent;
	if (a->key_len != b->key_len)
		return (long)a->key_len - (long)b->key_len;
	if (a->type != b->type)
		return (long)a->type - (long)b->type;

	if (a->key_len <= sizeof(a->inline_key)) {
		ka = &a->inline_key;
		kb =