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