volume.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* Volume handling.
  3 *
  4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7
  8#include <linux/fs.h>
  9#include <linux/slab.h>
 10#include <linux/namei.h>
 11#include "internal.h"
 12#include <trace/events/fscache.h>
 13
 14/*
 15 * Allocate and set up a volume representation.  We make sure all the fanout
 16 * directories are created and pinned.
 17 */
 18void cachefiles_acquire_volume(struct fscache_volume *vcookie)
 19{
 20	struct cachefiles_volume *volume;
 21	struct cachefiles_cache *cache = vcookie->cache->cache_priv;
 22	const struct cred *saved_cred;
 23	struct dentry *vdentry, *fan;
 24	size_t len;
 25	char *name;
 26	bool is_new = false;
 27	int ret, n_accesses, i;
 28
 29	_enter("");
 30
 31	volume = kzalloc(sizeof(struct cachefiles_volume), GFP_KERNEL);
 32	if (!volume)
 33		return;
 34	volume->vcookie = vcookie;
 35	volume->cache = cache;
 36	INIT_LIST_HEAD(&volume->cache_link);
 37
 38	cachefiles_begin_secure(cache, &saved_cred);
 39
 40	len = vcookie->key[0];
 41	name = kmalloc(len + 3, GFP_NOFS);
 42	if (!name)
 43		goto error_vol;
 44	name[0] = 'I';
 45	memcpy(name + 1, vcookie->key + 1, len);
 46	name[len + 1] = 0;
 47
 48retry:
 49	vdentry = cachefiles_get_directory(cache, cache->store, name, &is_new);
 50	if (IS_ERR(vdentry))
 51		goto error_name;
 52	volume->dentry = vdentry;
 53
 54	if (is_new) {
 55		if (!cachefiles_set_volume_xattr(volume))
 56			goto error_dir;
 57	} else {
 58		ret = cachefiles_check_volume_xattr(volume);
 59		if (ret < 0) {
 60			if (ret != -ESTALE)
 61				goto error_dir;
 62			vdentry = start_removing_dentry(cache->store, vdentry);
 63			if (!IS_ERR(vdentry))
 64				cachefiles_bury_object(cache, NULL, cache->store,
 65						       vdentry,
 66						       FSCACHE_VOLUME_IS_WEIRD);
 67			cachefiles_put_directory(volume->dentry);
 68			cond_resched();
 69			goto retry;
 70		}
 71	}
 72	
 73	for (i = 0; i < 256; i++) {
 74		sprintf(name, "@%02x", i);
 75		fan = cachefiles_get_directory(cache, vdentry, name, NULL);
 76		if (IS_ERR(fan))
 77			goto error_fan;
 78		volume->fanout[i] = fan;
 79	}
 80
 81	cachefiles_end_secure(cache, saved_cred);
 82
 83	vcookie->cache_priv = volume;
 84	n_accesses = atomic_inc_return(&vcookie->n_accesses); /* Stop wakeups on dec-to-0 */
 85	trace_fscache_access_volume(vcookie->debug_id, 0,
 86				    refcount_read(&vcookie->ref),
 87				    n_accesses, fscache_access_cache_pin);
 88
 89	spin_lock(&cache->object_list_lock);
 90	list_add(&volume->cache_link, &volume->cache->volumes);
 91	spin_unlock(&cache->object_list_lock);
 92
 93	kfree(name);
 94	return;
 95
 96error_fan:
 97	for (i = 0; i < 256; i++)
 98		cachefiles_put_directory(volume->fanout[i]);
 99error_dir:
100	cachefiles_put_directory(volume->dentry);
101error_name:
102	kfree(name);
103error_vol:
104	kfree(volume);
105	cachefiles_end_secure(cache, saved_cred);
106}
107
108/*
109 * Release a volume representation.
110 */
111static void __cachefiles_free_volume(struct cachefiles_volume *volume)
112{
113	int i;
114
115	_enter("");
116
117	volume->vcookie->cache_priv = NULL;
118
119	for (i = 0; i < 256; i++)
120		cachefiles_put_directory(volume->fanout[i]);
121	cachefiles_put_directory(volume->dentry);
122	kfree(volume);
123}
124
125void cachefiles_free_volume(struct fscache_volume *vcookie)
126{
127	struct cachefiles_volume *volume = vcookie->cache_priv;
128
129	if (volume) {
130		spin_lock(&volume->cache->object_list_lock);
131		list_del_init(&volume->cache_link);
132		spin_unlock(&volume->cache->object_list_lock);
133		__cachefiles_free_volume(volume);
134	}
135}
136
137void cachefiles_withdraw_volume(struct cachefiles_volume *volume)
138{
139	cachefiles_set_volume_xattr(volume);
140	__cachefiles_free_volume(volume);
141}