1 /* Blue Sky: File Systems in the Cloud
3 * Copyright (C) 2009 The Regents of the University of California
4 * Written by Michael Vrable <mvrable@cs.ucsd.edu>
15 /* Core filesystem. Different proxies, such as the NFSv3 one, interface to
16 * this, but the core actually tracks the data which is stored. So far we just
17 * implement an in-memory filesystem, but eventually this will be state which
18 * is persisted to the cloud. */
20 /* Return the current time, in microseconds since the epoch. */
21 int64_t bluesky_get_current_time()
24 g_get_current_time(&t);
25 return (int64_t)t.tv_sec * 1000000 + t.tv_usec;
28 /* Update an inode to indicate that a modification was made. This increases
29 * the change counter, updates the ctime to the current time, and optionally
30 * updates the mtime. */
31 void bluesky_inode_update_ctime(BlueSkyInode *inode, gboolean update_mtime)
33 int64_t now = bluesky_get_current_time();
34 inode->change_count++;
40 /* Compute the HMAC keyed-hash function using the given hash algorithm, data,
42 void compute_hmac(GChecksumType algo,
43 const guchar *data, gsize data_len,
44 const guchar *key, gsize key_len,
45 guint8 *buffer, gsize *digest_len)
52 case G_CHECKSUM_SHA256:
56 g_error("Unknown hash algorithm for HMAC: %d\n", algo);
59 gsize digest_size = g_checksum_type_get_length(algo);
61 guchar keybuf[block_size];
62 memset(keybuf, 0, block_size);
63 memcpy(keybuf, key, MIN(block_size, key_len));
64 for (int i = 0; i < block_size; i++)
67 GChecksum *csum1 = g_checksum_new(algo);
68 g_checksum_update(csum1, keybuf, block_size);
69 g_checksum_update(csum1, data, data_len);
70 guint8 digest[digest_size];
71 g_checksum_get_digest(csum1, digest, &digest_size);
73 memset(keybuf, 0, block_size);
74 memcpy(keybuf, key, MIN(block_size, key_len));
75 for (int i = 0; i < block_size; i++)
78 GChecksum *csum2 = g_checksum_new(algo);
79 g_checksum_update(csum2, keybuf, block_size);
80 g_checksum_update(csum2, digest, digest_size);
82 g_checksum_get_digest(csum2, buffer, digest_len);
84 g_checksum_free(csum1);
85 g_checksum_free(csum2);
88 /* Unfortunately a glib hash table is only guaranteed to be able to store
89 * 32-bit keys if we use the key directly. If we want 64-bit inode numbers,
90 * we'll have to allocate memory to store the 64-bit inumber, and use a pointer
91 * to it. Rather than allocate the memory for the key, we'll just include a
92 * pointer to the 64-bit inum stored in the inode itself, so that we don't need
93 * to do any more memory management. */
94 static guint bluesky_fs_key_hash_func(gconstpointer key)
96 uint64_t inum = *(const uint64_t *)key;
100 static gboolean bluesky_fs_key_equal_func(gconstpointer a, gconstpointer b)
102 uint64_t i1 = *(const uint64_t *)a;
103 uint64_t i2 = *(const uint64_t *)b;
107 /* Filesystem-level operations. A filesystem is like a directory tree that we
108 * are willing to export. */
109 BlueSkyFS *bluesky_new_fs(gchar *name)
111 BlueSkyFS *fs = g_new0(BlueSkyFS, 1);
112 fs->lock = g_mutex_new();
113 fs->name = g_strdup(name);
114 fs->inodes = g_hash_table_new(bluesky_fs_key_hash_func,
115 bluesky_fs_key_equal_func);
116 fs->next_inum = BLUESKY_ROOT_INUM + 1;
117 fs->store = bluesky_store_new("file");
122 /* Inode reference counting. */
123 void bluesky_inode_ref(BlueSkyInode *inode)
125 g_atomic_int_inc(&inode->refcount);
128 void bluesky_inode_unref(BlueSkyInode *inode)
130 if (g_atomic_int_dec_and_test(&inode->refcount)) {
131 g_error("Reference count for inode %lld dropped to zero!\n",
136 /* Allocate a fresh inode number which has not been used before within a
138 uint64_t bluesky_fs_alloc_inode(BlueSkyFS *fs)
142 g_mutex_lock(fs->lock);
143 inum = fs->next_inum;
145 g_mutex_unlock(fs->lock);
150 BlueSkyInode *bluesky_new_inode(uint64_t inum, BlueSkyFS *fs,
151 BlueSkyFileType type)
153 BlueSkyInode *i = g_new0(BlueSkyInode, 1);
155 i->lock = g_mutex_new();
162 case BLUESKY_REGULAR:
163 i->blocks = g_array_new(FALSE, TRUE, sizeof(BlueSkyBlock));
165 case BLUESKY_DIRECTORY:
166 i->dirents = g_sequence_new(bluesky_dirent_destroy);
167 i->dirhash = g_hash_table_new(g_str_hash, g_str_equal);
170 case BLUESKY_CHARACTER:
171 case BLUESKY_SYMLINK:
180 /* Retrieve an inode from the filesystem. Eventually this will be a cache and
181 * so we might need to go fetch the inode from elsewhere; for now all
182 * filesystem state is stored here. */
183 BlueSkyInode *bluesky_get_inode(BlueSkyFS *fs, uint64_t inum)
185 BlueSkyInode *inode = NULL;
187 g_mutex_lock(fs->lock);
188 inode = (BlueSkyInode *)g_hash_table_lookup(fs->inodes, &inum);
189 g_mutex_unlock(fs->lock);
194 /* Insert an inode into the filesystem inode cache. */
195 void bluesky_insert_inode(BlueSkyFS *fs, BlueSkyInode *inode)
197 g_mutex_lock(fs->lock);
198 g_hash_table_insert(fs->inodes, &inode->inum, inode);
199 g_mutex_unlock(fs->lock);