#include "bluesky-private.h"
+#define WRITEBACK_DELAY (5 * 1000000)
+#define CACHE_CLEAN_DELAY (30 * 1000000)
+
/* Filesystem caching and cache coherency. */
-static void flushd_inode(gpointer key, gpointer value, gpointer user_data)
+static void writeback_complete(gpointer a, gpointer i)
+{
+ BlueSkyInode *inode = (BlueSkyInode *)i;
+
+ g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
+ "Writeback for inode %"PRIu64" complete", inode->inum);
+
+ g_mutex_lock(inode->lock);
+
+ inode->change_commit = inode->change_pending;
+ if (inode->change_count == inode->change_commit) {
+ /* If inode is no longer dirty... */
+ inode->change_time = 0;
+ inode->change_pending = 0;
+ }
+
+ g_mutex_unlock(inode->lock);
+}
+
+/* Drop cached data for a given inode, if it is clean. inode must be locked. */
+static void drop_caches(BlueSkyInode *inode)
+{
+ if (inode->type == BLUESKY_REGULAR)
+ bluesky_file_drop_cached(inode);
+}
+
+static void flushd_inode(gpointer value, gpointer user_data)
{
BlueSkyFS *fs = (BlueSkyFS *)user_data;
BlueSkyInode *inode = (BlueSkyInode *)value;
- if (inode->change_count == inode->change_commit)
+ g_mutex_lock(inode->lock);
+
+ if (inode->change_count == inode->change_commit) {
+ uint64_t delay = bluesky_get_current_time() - inode->access_time;
+ if (delay >= CACHE_CLEAN_DELAY)
+ drop_caches(inode);
+ g_mutex_unlock(inode->lock);
+ bluesky_inode_unref(inode);
+ return;
+ }
+
+ if (inode->change_pending) {
+ /* Waiting for an earlier writeback to finish, so don't start a new
+ * writeback yet. */
+ g_mutex_unlock(inode->lock);
+ bluesky_inode_unref(inode);
+ return;
+ }
+
+ uint64_t elapsed = bluesky_get_current_time() - inode->change_time;
+ if (elapsed < WRITEBACK_DELAY) {
+ /* Give a bit more time before starting writeback. */
+ g_mutex_unlock(inode->lock);
+ bluesky_inode_unref(inode);
return;
+ }
+
+ inode->change_pending = inode->change_count;
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
"Starting flush of inode %"PRIu64, inode->inum);
- if (inode->type == BLUESKY_REGULAR)
- bluesky_file_flush(inode);
- bluesky_inode_flush(fs, inode);
+ /* Create a store barrier. All operations part of the writeback will be
+ * added to this barrier, so when the barrier completes we know that the
+ * writeback is finished. */
+ BlueSkyStoreAsync *barrier = bluesky_store_async_new(fs->store);
+ barrier->op = STORE_OP_BARRIER;
+
+ bluesky_inode_start_sync(inode, barrier);
+
+ bluesky_store_async_add_notifier(barrier, writeback_complete, inode);
+ bluesky_store_async_submit(barrier);
+ bluesky_store_async_unref(barrier);
+
+ g_mutex_unlock(inode->lock);
+ bluesky_inode_unref(inode);
}
/* Scan through the cache for dirty data and start flushing it to stable
* storage. This does not guarantee that data is committed when it returns.
* Instead, this can be called occasionally to ensure that dirty data is
- * gradually flushed. */
+ * gradually flushed.
+ *
+ * We do not want to hold the filesystem lock while flushing individual inodes,
+ * a that could lead to deadlock. So first scan through the inode table to get
+ * a reference to all inodes, then process that queue of inodes after dropping
+ * the filesystem lock. */
+static void gather_inodes(gpointer key, gpointer value, gpointer user_data)
+{
+ GSList **list = (GSList **)user_data;
+ *list = g_slist_prepend(*list, value);
+ bluesky_inode_ref((BlueSkyInode *)value);
+}
+
void bluesky_flushd_invoke(BlueSkyFS *fs)
{
- g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
- "Writeout process invoked");
+ GSList *list = NULL;
g_mutex_lock(fs->lock);
- g_hash_table_foreach(fs->inodes, flushd_inode, fs);
+ g_hash_table_foreach(fs->inodes, gather_inodes, &list);
g_mutex_unlock(fs->lock);
+
+ list = g_slist_reverse(list);
+ g_slist_foreach(list, flushd_inode, fs);
+
+ g_slist_free(list);
}