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>
14 #include "bluesky-private.h"
16 // Rough size limit for a log segment. This is not a firm limit and there are
17 // no absolute guarantees on the size of a log segment.
18 #define CLOUDLOG_SEGMENT_SIZE (4 << 20)
20 BlueSkyCloudID bluesky_cloudlog_new_id()
23 bluesky_crypt_random_bytes((uint8_t *)&id.bytes, sizeof(id));
27 gchar *bluesky_cloudlog_id_to_string(BlueSkyCloudID id)
29 char buf[sizeof(BlueSkyCloudID) * 2 + 1];
32 for (int i = 0; i < sizeof(BlueSkyCloudID); i++) {
33 sprintf(&buf[2*i], "%02x", (uint8_t)(id.bytes[i]));
39 BlueSkyCloudID bluesky_cloudlog_id_from_string(const gchar *idstr)
42 memset(&id, 0, sizeof(id));
43 for (int i = 0; i < 2*sizeof(BlueSkyCloudID); i++) {
46 g_warning("Short cloud id: %s\n", idstr);
50 if (c >= '0' && c <= '9')
52 else if (c >= 'a' && c <= 'f')
55 g_warning("Bad character in cloud id: %s\n", idstr);
56 id.bytes[i / 2] += val << (i % 2 ? 0 : 4);
61 gboolean bluesky_cloudlog_equal(gconstpointer a, gconstpointer b)
63 BlueSkyCloudID *id1 = (BlueSkyCloudID *)a, *id2 = (BlueSkyCloudID *)b;
65 return memcmp(id1, id2, sizeof(BlueSkyCloudID)) == 0;
68 guint bluesky_cloudlog_hash(gconstpointer a)
70 BlueSkyCloudID *id = (BlueSkyCloudID *)a;
72 // Assume that bits in the ID are randomly chosen so that any subset of the
73 // bits can be used as a hash key.
74 return *(guint *)(&id->bytes);
77 /* Formatting of cloud log segments. This handles grouping items together
78 * before writing a batch to the cloud, handling indirection through items like
79 * the inode map, etc. */
81 BlueSkyCloudLog *bluesky_cloudlog_new(BlueSkyFS *fs)
83 BlueSkyCloudLog *log = g_new0(BlueSkyCloudLog, 1);
85 log->lock = g_mutex_new();
86 log->cond = g_cond_new();
88 log->type = LOGTYPE_UNKNOWN;
89 log->id = bluesky_cloudlog_new_id();
90 log->links = g_array_new(FALSE, TRUE, sizeof(BlueSkyCloudLog *));
91 g_atomic_int_set(&log->refcount, 1);
96 /* Helper function for updating memory usage statistics for a filesystem (the
97 * cache_log_* variables). This will increment (type=1) or decrement (type=-1)
98 * the counter associated with the current state of the cloud log item. The
99 * item should be locked or otherwise protected from concurrent access. */
100 void bluesky_cloudlog_stats_update(BlueSkyCloudLog *log, int type)
102 BlueSkyFS *fs = log->fs;
104 if (log->location_flags & CLOUDLOG_CLOUD) {
105 g_atomic_int_add(&fs->cache_log_cloud, type);
106 } else if (log->location_flags & CLOUDLOG_JOURNAL) {
107 g_atomic_int_add(&fs->cache_log_journal, type);
108 } else if (log->pending_write & CLOUDLOG_JOURNAL) {
109 g_atomic_int_add(&fs->cache_log_journal, type);
110 } else if (log->data != NULL) {
111 g_atomic_int_add(&fs->cache_log_dirty, type);
115 /* The reference held by the hash table does not count towards the reference
116 * count. When a new object is created, it initially has a reference count of
117 * 1 for the creator, and similarly fetching an item from the hash table will
118 * also create a reference. If the reference count drops to zero,
119 * bluesky_cloudlog_unref attempts to remove the object from the hash
120 * table--but there is a potential race since another thread might read the
121 * object from the hash table at the same time. So an object with a reference
122 * count of zero may still be resurrected, in which case we need to abort the
123 * destruction. Once the object is gone from the hash table, and if the
124 * reference count is still zero, it can actually be deleted. */
125 void bluesky_cloudlog_ref(BlueSkyCloudLog *log)
130 g_atomic_int_inc(&log->refcount);
133 void bluesky_cloudlog_unref(BlueSkyCloudLog *log)
138 if (g_atomic_int_dec_and_test(&log->refcount)) {
139 BlueSkyFS *fs = log->fs;
141 g_mutex_lock(fs->lock);
142 if (g_atomic_int_get(&log->refcount) > 0) {
143 g_mutex_unlock(fs->lock);
147 g_hash_table_remove(fs->locations, &log->id);
148 g_mutex_unlock(fs->lock);
150 bluesky_cloudlog_stats_update(log, -1);
151 log->type = LOGTYPE_INVALID;
152 g_mutex_free(log->lock);
153 g_cond_free(log->cond);
154 for (int i = 0; i < log->links->len; i++) {
155 BlueSkyCloudLog *c = g_array_index(log->links,
156 BlueSkyCloudLog *, i);
157 bluesky_cloudlog_unref(c);
159 g_array_unref(log->links);
160 bluesky_string_unref(log->data);
165 /* Start a write of the object to the local log. */
166 void bluesky_cloudlog_sync(BlueSkyCloudLog *log)
168 bluesky_log_item_submit(log, log->fs->log);
171 /* Add the given entry to the global hash table containing cloud log entries.
172 * Takes ownership of the caller's reference. */
173 void bluesky_cloudlog_insert(BlueSkyCloudLog *log)
175 g_mutex_lock(log->fs->lock);
176 g_hash_table_insert(log->fs->locations, &log->id, log);
177 g_mutex_unlock(log->fs->lock);
184 uint32_t pointer_count;
185 } __attribute__((packed));
189 BlueSkyCloudPointer location;
190 } __attribute__((packed));
194 struct logref refs[0];
197 /* Ensure that a cloud log item is loaded in memory, and if not read it in.
198 * TODO: Make asynchronous, and make this also fetch from the cloud. Right now
199 * we only read from the log. Log item must be locked. */
200 void bluesky_cloudlog_fetch(BlueSkyCloudLog *log)
202 if (log->data != NULL)
205 if ((log->location_flags | log->pending_write) & CLOUDLOG_JOURNAL) {
206 bluesky_cloudlog_stats_update(log, -1);
207 log->data = bluesky_log_map_object(log->fs, -1, log->log_seq,
208 log->log_offset, log->log_size);
209 bluesky_cloudlog_stats_update(log, 1);
210 } else if (log->location_flags & CLOUDLOG_CLOUD) {
211 bluesky_cloudlog_stats_update(log, -1);
212 log->data = bluesky_log_map_object(log->fs, log->location.directory,
213 log->location.sequence,
214 log->location.offset,
216 bluesky_cloudlog_stats_update(log, 1);
218 g_error("Unable to fetch cloudlog entry!");
221 g_cond_broadcast(log->cond);
224 BlueSkyCloudPointer bluesky_cloudlog_serialize(BlueSkyCloudLog *log,
227 BlueSkyCloudLogState *state = fs->log_state;
229 if (log->location_flags & CLOUDLOG_CLOUD) {
230 return log->location;
233 for (int i = 0; i < log->links->len; i++) {
234 BlueSkyCloudLog *ref = g_array_index(log->links,
235 BlueSkyCloudLog *, i);
237 bluesky_cloudlog_serialize(ref, fs);
240 g_mutex_lock(log->lock);
241 bluesky_cloudlog_fetch(log);
242 g_assert(log->data != NULL);
244 bluesky_cloudlog_stats_update(log, -1);
246 /* TODO: Right now offset/size are set to the raw data, but we should add
247 * header parsing to the code which loads objects back in. */
248 log->location = state->location;
249 log->location.offset = state->data->len + sizeof(struct log_header);
250 log->location.size = log->data->len;
251 /* = sizeof(struct log_header) + sizeof(BlueSkyCloudID) * 0
254 struct log_header header;
255 memcpy(header.magic, "AgI ", 4);
256 header.size = GUINT32_TO_LE(log->location.size);
258 header.pointer_count = GUINT32_TO_LE(0);
260 g_string_append_len(state->data, (const char *)&header, sizeof(header));
261 g_string_append_len(state->data, log->data->data, log->data->len);
263 log->location_flags |= CLOUDLOG_CLOUD;
264 bluesky_cloudlog_stats_update(log, 1);
265 g_mutex_unlock(log->lock);
267 if (state->data->len > CLOUDLOG_SEGMENT_SIZE)
268 bluesky_cloudlog_flush(fs);
270 return log->location;
273 /* Finish up a partially-written cloud log segment and flush it to storage. */
274 void bluesky_cloudlog_flush(BlueSkyFS *fs)
276 BlueSkyCloudLogState *state = fs->log_state;
277 if (state->data == NULL || state->data->len == 0)
280 /* TODO: Append some type of commit record to the log segment? */
282 g_print("Serializing %zd bytes of data to cloud\n", state->data->len);
284 BlueSkyStoreAsync *async = bluesky_store_async_new(fs->store);
285 async->op = STORE_OP_PUT;
286 async->key = g_strdup_printf("log-%08d-%08d",
287 state->location.directory,
288 state->location.sequence);
289 async->data = bluesky_string_new_from_gstring(state->data);
290 bluesky_store_async_submit(async);
291 //bluesky_store_async_wait(async);
292 bluesky_store_async_unref(async);
294 state->location.sequence++;
295 state->location.offset = 0;
296 state->data = g_string_new("");