* TODO: Licensing
*/
+#define _GNU_SOURCE
+#define _ATFILE_SOURCE
+
+#include <stdio.h>
#include <stdint.h>
+#include <stdlib.h>
#include <glib.h>
#include <string.h>
+#include <errno.h>
#include <inttypes.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
#include "bluesky-private.h"
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.
+ *
+ * Note that some of this code relies on the fact that only this thread of
+ * control (running flushd_cloud) is manipulating the inode map, and so
+ * concurrent updates to the inode map are prevented even without the
+ * filesystem lock held. Take great care if allowing multi-threaded access to
+ * the inode map... */
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. */
+ BlueSkyCloudLog *marker = bluesky_log_get_commit_point(fs);
+ 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_lock(inode->lock);
- flushd_dirty_inode(inode);
+ g_assert(inode->change_cloud == inode->change_commit);
g_mutex_lock(fs->lock);
bluesky_list_unlink(&fs->dirty_list, inode->dirty_list);
inode->dirty_list = NULL;
g_mutex_unlock(fs->lock);
BlueSkyCloudLog *log = inode->committed_item;
- bluesky_cloudlog_ref(log);
+ inode->committed_item = NULL;
g_mutex_unlock(inode->lock);
if (log != NULL)
g_mutex_lock(fs->lock);
}
-
g_mutex_unlock(fs->lock);
+
+ /* Write out any updated inode map entries, so that all inodes just written
+ * can be located, and then a final commit record. */
+ BlueSkyCloudLog *commit_record = bluesky_inode_map_serialize(fs);
+ if (commit_record != NULL) {
+ bluesky_cloudlog_serialize(commit_record, fs);
+ } else {
+ g_print("No need for a checkpoint record...\n");
+ }
+
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);
+ }
+
+ bluesky_log_write_commit_point(fs, marker);
+ bluesky_cloudlog_unref(commit_record);
+
+ g_print("All segments have been flushed, journal < %d is clean\n",
+ journal_seq_start);
+
+ fs->log->journal_watermark = journal_seq_start;
+
+ bluesky_inode_map_minimize(fs);
}
/* Drop cached data for a given inode, if it is clean. inode must be locked. */
{
if (inode->type == BLUESKY_REGULAR)
bluesky_file_drop_cached(inode);
+
+ BlueSkyCloudLog *log = inode->committed_item;
+ if (log != NULL) {
+ g_mutex_lock(log->lock);
+ if (log->data != NULL
+ && g_atomic_int_get(&log->data_lock_count) == 0
+ && (log->location_flags != 0))
+ {
+ bluesky_cloudlog_stats_update(log, -1);
+ bluesky_string_unref(log->data);
+ log->data = NULL;
+ bluesky_cloudlog_stats_update(log, 1);
+ }
+ g_mutex_unlock(log->lock);
+ }
}
/* Drop clean data from the cache if needed. Clean data should generally be
* memory-mapped from log file or similar, so the kernel can drop this clean
* data from memory for us and hence memory management isn't too important.
* Mainly, we'll want to drop references to data that hasn't been accessed in a
- * while so that it is possible to reclaim log segments on disk. */
-static void flushd_clean(BlueSkyFS *fs)
+ * while so that it is possible to reclaim log segments on disk.
+ *
+ * If aggressive is set, try much harder to drop data from the caches to free
+ * up space. */
+static void flushd_clean(BlueSkyFS *fs, int aggressive)
{
g_mutex_lock(fs->lock);
inode = fs->accessed_list.prev->data;
uint64_t elapsed = bluesky_get_current_time() - inode->access_time;
- if (elapsed < CACHE_DROP_DELAY)
+ if (elapsed < CACHE_DROP_DELAY && !aggressive)
break;
if (bluesky_verbose) {
g_mutex_unlock(fs->lock);
}
+/* Scan through all currently-stored files in the journal/cache and garbage
+ * collect old unused ones, if needed. */
+static void gather_cachefiles(gpointer key, gpointer value, gpointer user_data)
+{
+ GList **files = (GList **)user_data;
+ *files = g_list_prepend(*files, value);
+}
+
+static gint compare_cachefiles(gconstpointer a, gconstpointer b)
+{
+ int64_t ta, tb;
+
+ ta = ((BlueSkyCacheFile *)a)->atime;
+ tb = ((BlueSkyCacheFile *)b)->atime;
+ if (ta < tb)
+ return -1;
+ else if (ta > tb)
+ return 1;
+ else
+ return 0;
+}
+
+void bluesky_cachefile_gc(BlueSkyFS *fs)
+{
+ GList *files = NULL;
+
+ g_mutex_lock(fs->log->mmap_lock);
+ g_hash_table_foreach(fs->log->mmap_cache, gather_cachefiles, &files);
+
+ /* Sort based on atime. The atime should be stable since it shouln't be
+ * updated except by threads which can grab the mmap_lock, which we already
+ * hold. */
+ files = g_list_sort(files, compare_cachefiles);
+
+ /* Walk the list of files, starting with the oldest, deleting files if
+ * possible until enough space has been reclaimed. */
+ g_print("\nScanning cache: (total size = %d kB)\n", fs->log->disk_used);
+ while (files != NULL) {
+ BlueSkyCacheFile *cachefile = (BlueSkyCacheFile *)files->data;
+ /* Try to lock the structure, but if the lock is held by another thread
+ * then we'll just skip the file on this pass. */
+ if (g_mutex_trylock(cachefile->lock)) {
+ int64_t age = bluesky_get_current_time() - cachefile->atime;
+ if (bluesky_verbose) {
+ g_print("%s addr=%p mapcount=%d refcount=%d size=%d atime_age=%f",
+ cachefile->filename, cachefile->addr, cachefile->mapcount,
+ cachefile->refcount, cachefile->disk_used, age / 1e6);
+ if (cachefile->fetching)
+ g_print(" (fetching)");
+ g_print("\n");
+ }
+
+ gboolean deletion_candidate = FALSE;
+ if (g_atomic_int_get(&fs->log->disk_used)
+ > bluesky_options.cache_size
+ && 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) {
+ if (bluesky_verbose) {
+ g_print(" ...deleting\n");
+ }
+ if (unlinkat(fs->log->dirfd, cachefile->filename, 0) < 0) {
+ fprintf(stderr, "Unable to unlink journal %s: %m\n",
+ cachefile->filename);
+ }
+
+ g_atomic_int_add(&fs->log->disk_used, -cachefile->disk_used);
+ g_hash_table_remove(fs->log->mmap_cache, cachefile->filename);
+ bluesky_rangeset_free(cachefile->items);
+ if (cachefile->prefetches != NULL)
+ bluesky_rangeset_free(cachefile->prefetches);
+ g_mutex_unlock(cachefile->lock);
+ g_mutex_free(cachefile->lock);
+ g_cond_free(cachefile->cond);
+ g_free(cachefile->filename);
+ g_free(cachefile);
+ } else {
+ g_mutex_unlock(cachefile->lock);
+ }
+ }
+ files = g_list_delete_link(files, files);
+ }
+ g_list_free(files);
+ g_print("\nEnding cache size: %d kB\n", fs->log->disk_used);
+
+ g_mutex_unlock(fs->log->mmap_lock);
+}
+
/* Run the flush daemon for a single iteration, though if it is already
* executing returns immediately. */
static gpointer flushd_task(BlueSkyFS *fs)
{
if (!g_mutex_trylock(fs->flushd_lock))
return NULL;
+
+ g_print("\nCloudlog cache: %d dirty, %d writeback, %d journal, %d cloud\n",
+ g_atomic_int_get(&fs->cache_log_dirty),
+ g_atomic_int_get(&fs->cache_log_writeback),
+ g_atomic_int_get(&fs->cache_log_journal),
+ g_atomic_int_get(&fs->cache_log_cloud));
+
flushd_dirty(fs);
flushd_cloud(fs);
- flushd_clean(fs);
+ flushd_clean(fs, 0);
+ bluesky_cachefile_gc(fs);
+
+ /* If running out of disk cache space, make another more aggressive pass to
+ * free up space. */
+ if (g_atomic_int_get(&fs->log->disk_used) > bluesky_options.cache_size) {
+ g_print("Still short on disk space, trying again to free space...\n");
+ flushd_clean(fs, 1);
+ bluesky_cachefile_gc(fs);
+ }
+
g_mutex_unlock(fs->flushd_lock);
return NULL;
g_thread_create((GThreadFunc)flushd_task, fs, FALSE, NULL);
}
-void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
+/* How urgent is flushing out data? Returns one of several values:
+ * 0 - memory state is fine
+ * 1 - should launch flushd if not already running
+ * 2 - should block writers until memory frees up
+ */
+static int compute_pressure(BlueSkyFS *fs)
{
+ /* LEVEL 2 */
+ /* Too much dirty data in memory? */
+ if (g_atomic_int_get(&fs->cache_dirty)
+ + g_atomic_int_get(&fs->cache_log_dirty)
+ > bluesky_watermark_high_dirty)
+ return 2;
+
+ /* Too much uncommitted data in the journal on disk, not yet flushed to the
+ * cloud? */
+ printf("Dirty journals: %d to %d\n",
+ fs->log->journal_watermark, fs->log->seq_num);
+ int dirty_limit;
+ dirty_limit = bluesky_options.cache_size / (LOG_SEGMENT_SIZE / 1024) / 2;
+ int dirty_journals = fs->log->seq_num - fs->log->journal_watermark + 1;
+ if (dirty_journals > 1 && dirty_journals >= dirty_limit) {
+ printf("Too many dirty journals (%d >= %d)\n",
+ dirty_journals, dirty_limit);
+ return 2;
+ }
+
+ /* LEVEL 1 */
if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_medium_dirty)
+ return 1;
+
+ if (dirty_journals > 1 && dirty_journals > dirty_limit / 2) {
+ printf("Many dirty journals (%d), should start writeback\n",
+ dirty_journals);
+ return 1;
+ }
+
+ return 0;
+}
+
+void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
+{
+ int pressure = compute_pressure(fs);
+ if (pressure == 0)
return;
if (bluesky_verbose) {
/* If the system is under heavy memory pressure, actually delay execution
* so the flush daemon can catch up. */
- while (g_atomic_int_get(&fs->cache_dirty)
- + g_atomic_int_get(&fs->cache_log_dirty)
- > bluesky_watermark_high_dirty) {
+ while (pressure > 1) {
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
"Waiting due to memory pressure, dirty=%d + %d",
g_atomic_int_get(&fs->cache_dirty),
g_atomic_int_get(&fs->cache_log_dirty));
g_mutex_lock(fs->lock);
- g_cond_wait(fs->flushd_cond, fs->lock);
+ pressure = compute_pressure(fs);
+ if (pressure > 1)
+ g_cond_wait(fs->flushd_cond, fs->lock);
g_mutex_unlock(fs->lock);
+ pressure = compute_pressure(fs);
}
}
projects / bluesky.git / blobdiff