BlueSkyCloudPointer location;
GList *inode_list;
GSList *writeback_list; // Items which are being serialized right now
+ GList *pending_segments; // Segments which are being uploaded now
};
gboolean bluesky_cloudlog_equal(gconstpointer a, gconstpointer b);
/* A count of the disk space consumed (in 1024-byte units) by all files
* tracked by mmap_cache (whether mapped or not, actually). */
gint disk_used;
+
+ /* The smallest journal sequence number which may still contain data that
+ * must be preserved (since it it not yet in the cloud). */
+ int journal_watermark;
};
/* An object for tracking log files which are stored locally--either the
int clouddir, int log_seq);
void bluesky_cachefile_gc(BlueSkyFS *fs);
+/* Used to track log segments that are being written to the cloud. */
+typedef struct {
+ BlueSkyRCStr *data;
+ GSList *items;
+ GMutex *lock;
+ GCond *cond;
+ gboolean complete;
+} SerializedRecord;
+
#ifdef __cplusplus
}
#endif
g_mutex_unlock(fs->lock);
}
-/* Try to flush dirty data to the cloud.
- * TODO: Rewrite this to work on cloud log items rather than inodes, so we can
- * better track which logs are fully synchronized to the cloud and can be
- * garbage collected if needed? */
+/* Try to flush dirty data to the cloud. This will take a snapshot of the
+ * entire filesystem (though only point-in-time consistent for isolated inodes
+ * and not the filesystem as a whole) and ensure all data is written to the
+ * cloud. When the write completes, we will allow old journal segments (those
+ * that were fully written _before_ the snapshot process started) to be garbage
+ * collected. Newer journal segments can't be collected yet since they may
+ * still contain data which has not been written persistently to the cloud. */
static void flushd_cloud(BlueSkyFS *fs)
{
- int64_t start_time = bluesky_get_current_time();
g_mutex_lock(fs->lock);
+ /* TODO: Locking? Since we're reading a single variable this is probably
+ * atomic but a lock could be safer. */
+ int journal_seq_start = fs->log->seq_num;
+
while (1) {
BlueSkyInode *inode;
if (fs->dirty_list.prev == NULL)
"Flushing inode %"PRIu64" to cloud", inode->inum);
}
- /* Stop processing dirty inodes if we both have enough memory available
- * and the oldest inode is sufficiently new that it need not be flushed
- * out. */
- uint64_t elapsed = bluesky_get_current_time() - inode->change_time;
- if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_low_dirty
- && elapsed < WRITEBACK_DELAY)
- break;
- if (inode->change_time > start_time)
- break;
-
bluesky_inode_ref(inode);
g_mutex_unlock(fs->lock);
g_mutex_unlock(fs->lock);
bluesky_cloudlog_flush(fs);
+
+ /* Wait until all segments have been written to the cloud, so that it
+ * becomes safe to free up journal segments. */
+ while (fs->log_state->pending_segments != NULL) {
+ SerializedRecord *segment
+ = (SerializedRecord *)fs->log_state->pending_segments->data;
+ g_mutex_lock(segment->lock);
+ while (!segment->complete)
+ g_cond_wait(segment->cond, segment->lock);
+ g_mutex_unlock(segment->lock);
+
+ g_mutex_free(segment->lock);
+ g_cond_free(segment->cond);
+ g_free(segment);
+
+ fs->log_state->pending_segments
+ = g_list_delete_link(fs->log_state->pending_segments,
+ fs->log_state->pending_segments);
+ }
+
+ g_print("All segments have been flushed, journal < %d is clean\n",
+ journal_seq_start);
+
+ fs->log->journal_watermark = journal_seq_start;
}
/* Drop cached data for a given inode, if it is clean. inode must be locked. */
return log->location;
}
-typedef struct {
- BlueSkyRCStr *data;
- GSList *items;
-} SerializedRecord;
-
static void cloudlog_flush_complete(BlueSkyStoreAsync *async,
SerializedRecord *record)
{
g_print("Write of %s to cloud complete, status = %d\n",
async->key, async->result);
+ g_mutex_lock(record->lock);
if (async->result >= 0) {
while (record->items != NULL) {
BlueSkyCloudLog *item = (BlueSkyCloudLog *)record->items->data;
}
bluesky_string_unref(record->data);
+ record->data = NULL;
g_slist_free(record->items);
- g_free(record);
+ record->items = NULL;
+ record->complete = TRUE;
+ g_cond_broadcast(record->cond);
} else {
g_print("Write should be resubmitted...\n");
record);
bluesky_store_async_unref(async2);
}
+ g_mutex_unlock(record->lock);
}
/* Finish up a partially-written cloud log segment and flush it to storage. */
SerializedRecord *record = g_new0(SerializedRecord, 1);
record->data = bluesky_string_new_from_gstring(state->data);
record->items = state->writeback_list;
+ record->lock = g_mutex_new();
+ record->cond = g_cond_new();
state->writeback_list = NULL;
BlueSkyStoreAsync *async = bluesky_store_async_new(fs->store);
record);
bluesky_store_async_unref(async);
+ state->pending_segments = g_list_prepend(state->pending_segments, record);
+
state->location.sequence++;
state->location.offset = 0;
state->data = g_string_new("");
g_print(" (fetching)");
g_print("\n");
+ gboolean deletion_candidate = FALSE;
if (g_atomic_int_get(&fs->log->disk_used) > DISK_CACHE_SIZE_TARGET
&& g_atomic_int_get(&cachefile->refcount) == 0
&& g_atomic_int_get(&cachefile->mapcount) == 0)
{
+ deletion_candidate = TRUE;
+ }
+
+ /* Don't allow journal files to be reclaimed until all data is
+ * known to be durably stored in the cloud. */
+ if (cachefile->type == CLOUDLOG_JOURNAL
+ && cachefile->log_seq >= fs->log->journal_watermark)
+ {
+ deletion_candidate = FALSE;
+ }
+
+ if (deletion_candidate) {
g_print(" ...deleting\n");
if (unlinkat(fs->log->dirfd, cachefile->filename, 0) < 0) {
fprintf(stderr, "Unable to unlink journal %s: %m\n",
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