From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Wed, 18 Aug 2010 20:45:40 +0000 (-0700)
Subject: Track journal files which contain dirty data and which can be reclaimed.
X-Git-Url: http://git.vrable.net/?p=bluesky.git;a=commitdiff_plain;h=b8885660a453f0f1f30c9fed196b01a397482a19

Track journal files which contain dirty data and which can be reclaimed.
---

diff --git a/bluesky/bluesky-private.h b/bluesky/bluesky-private.h
index 73f38e1..c066fd3 100644
--- a/bluesky/bluesky-private.h
+++ b/bluesky/bluesky-private.h
@@ -192,6 +192,13 @@ struct _BlueSkyCloudLog {
     int location_flags;
     int pending_read, pending_write;
 
+    // If the object is not yet flushed to cloud storage but is written to a
+    // journal file locally, a reference to that journal file so that we can
+    // keep the dirty_refs count updated.  When the object is deleted or
+    // becomes clean, decrement the dirty_refs counter of the journal file and
+    // set this pointer to NULL.
+    BlueSkyCacheFile *dirty_journal;
+
     // A stable identifier for the object (only changes when authenticated data
     // is written out, but stays the same when the in-cloud cleaner relocates
     // the object).
@@ -248,12 +255,16 @@ uint32_t crc32c(uint32_t crc, const char *buf, unsigned int length);
 uint32_t crc32c_finalize(uint32_t crc);
 
 struct _BlueSkyLog {
+    BlueSkyFS *fs;
     char *log_directory;
     GAsyncQueue *queue;
     int fd, dirfd;
     int seq_num;
     GSList *committed;
 
+    /* The currently-open log file. */
+    BlueSkyCacheFile *current_log;
+
     /* Cache of log segments which have been memory-mapped. */
     GMutex *mmap_lock;
     GHashTable *mmap_cache;
@@ -279,8 +290,13 @@ struct _BlueSkyCacheFile {
     size_t len;
     BlueSkyFS *fs;
     BlueSkyLog *log;
-    gboolean fetching, ready;
+    gboolean fetching, ready;   // Cloud data: downloading or ready for use
     int64_t atime;              // Access time, for cache management
+
+    /* Journal: Count of objects which are not yet committed to cloud storage
+     * but need to be; a non-zero value prevents the journal file from being
+     * deleted. */
+    gint dirty_refs;
 };
 
 BlueSkyLog *bluesky_log_new(const char *log_directory);
@@ -289,7 +305,10 @@ void bluesky_log_finish_all(GList *log_items);
 BlueSkyRCStr *bluesky_log_map_object(BlueSkyFS *fs, int log_dir, int log_seq,
                                      int log_offset, int log_size);
 void bluesky_mmap_unref(BlueSkyCacheFile *mmap);
+void bluesky_cachefile_unref(BlueSkyCacheFile *cachefile);
 
+BlueSkyCacheFile *bluesky_cachefile_lookup(BlueSkyFS *fs,
+                                           int clouddir, int log_seq);
 void bluesky_cachefile_gc(BlueSkyFS *fs);
 
 #ifdef __cplusplus
diff --git a/bluesky/cloudlog.c b/bluesky/cloudlog.c
index 3809b00..196eeb8 100644
--- a/bluesky/cloudlog.c
+++ b/bluesky/cloudlog.c
@@ -158,6 +158,8 @@ void bluesky_cloudlog_unref(BlueSkyCloudLog *log)
         }
         g_array_unref(log->links);
         bluesky_string_unref(log->data);
+        if (log->dirty_journal != NULL)
+            g_atomic_int_add(&log->dirty_journal->dirty_refs, -1);
         g_free(log);
     }
 }
@@ -260,8 +262,14 @@ BlueSkyCloudPointer bluesky_cloudlog_serialize(BlueSkyCloudLog *log,
     g_string_append_len(state->data, (const char *)&header, sizeof(header));
     g_string_append_len(state->data, log->data->data, log->data->len);
 
+    /* TODO: We should mark the objects as committed on the cloud until the
+     * data is flushed and acknowledged. */
     log->location_flags |= CLOUDLOG_CLOUD;
     bluesky_cloudlog_stats_update(log, 1);
+    if (log->dirty_journal != NULL) {
+        g_atomic_int_add(&log->dirty_journal->dirty_refs, -1);
+        log->dirty_journal = NULL;
+    }
     g_mutex_unlock(log->lock);
 
     if (state->data->len > CLOUDLOG_SEGMENT_SIZE)
diff --git a/bluesky/debug.c b/bluesky/debug.c
index 207cb7b..0a5f254 100644
--- a/bluesky/debug.c
+++ b/bluesky/debug.c
@@ -56,9 +56,9 @@ static void cache_dump(gpointer key, gpointer value, gpointer user_data)
     BlueSkyCacheFile *cache = (BlueSkyCacheFile *)value;
 
     int64_t age = bluesky_get_current_time() - cache->atime;
-    g_print("%s addr=%p mapcount=%d refcount=%d atime_age=%f",
+    g_print("%s addr=%p mapcount=%d refcount=%d dirty=%d atime_age=%f",
             cache->filename, cache->addr, cache->mapcount, cache->refcount,
-            age / 1e6);
+            cache->dirty_refs, age / 1e6);
     if (cache->fetching)
         g_print(" (fetching)");
     g_print("\n");
diff --git a/bluesky/inode.c b/bluesky/inode.c
index 2696713..d284479 100644
--- a/bluesky/inode.c
+++ b/bluesky/inode.c
@@ -109,6 +109,7 @@ BlueSkyFS *bluesky_init_fs(gchar *name, BlueSkyStore *store)
         if (fs != NULL) {
             fs->store = store;
             fs->log = bluesky_log_new("journal");
+            fs->log->fs = fs;
             g_print("Loaded filesystem superblock\n");
             g_free(fs->name);
             fs->name = g_strdup(name);
@@ -121,6 +122,7 @@ BlueSkyFS *bluesky_init_fs(gchar *name, BlueSkyStore *store)
     BlueSkyFS *fs = bluesky_new_fs(name);
     fs->store = store;
     fs->log = bluesky_log_new("journal");
+    fs->log->fs = fs;
 
     BlueSkyInode *root = bluesky_new_inode(BLUESKY_ROOT_INUM, fs,
                                            BLUESKY_DIRECTORY);
diff --git a/bluesky/log.c b/bluesky/log.c
index 976e32e..66b4edb 100644
--- a/bluesky/log.c
+++ b/bluesky/log.c
@@ -103,6 +103,11 @@ static gboolean log_open(BlueSkyLog *log)
         log->fd = -1;
     }
 
+    if (log->current_log != NULL) {
+        bluesky_cachefile_unref(log->current_log);
+        log->current_log = NULL;
+    }
+
     while (log->fd < 0) {
         g_snprintf(logname, sizeof(logname), "journal-%08d", log->seq_num);
         log->fd = openat(log->dirfd, logname, O_CREAT|O_WRONLY|O_EXCL, 0600);
@@ -116,6 +121,10 @@ static gboolean log_open(BlueSkyLog *log)
         }
     }
 
+    log->current_log = bluesky_cachefile_lookup(log->fs, -1, log->seq_num);
+    g_assert(log->current_log != NULL);
+    g_mutex_unlock(log->current_log->lock);
+
     if (ftruncate(log->fd, LOG_SEGMENT_SIZE) < 0) {
         fprintf(stderr, "Unable to truncate logfile %s: %m\n", logname);
     }
@@ -204,6 +213,13 @@ static gpointer log_thread(gpointer d)
 
         offset += sizeof(header) + sizeof(footer) + item->data->len;
 
+        /* Since we have just written a new dirty object to the journal,
+         * increment the count of live dirty objects in that journal file.  The
+         * count will be decremented when objects are deleted or written to the
+         * cloud. */
+        g_atomic_int_add(&log->current_log->dirty_refs, 1);
+        item->dirty_journal = log->current_log;
+
         /* Replace the log item's string data with a memory-mapped copy of the
          * data, now that it has been written to the log file.  (Even if it
          * isn't yet on disk, it should at least be in the page cache and so
@@ -481,16 +497,16 @@ void bluesky_cachefile_gc(BlueSkyFS *fs)
          * 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;
-            g_print("%s addr=%p mapcount=%d refcount=%d atime_age=%f",
+            g_print("%s addr=%p mapcount=%d refcount=%d dirty=%d atime_age=%f",
                     cachefile->filename, cachefile->addr, cachefile->mapcount,
-                    cachefile->refcount, age / 1e6);
+                    cachefile->refcount, cachefile->dirty_refs, age / 1e6);
             if (cachefile->fetching)
                 g_print(" (fetching)");
             g_print("\n");
 
             if (g_atomic_int_get(&cachefile->refcount) == 0
                 && g_atomic_int_get(&cachefile->mapcount) == 0
-                && cachefile->type == CLOUDLOG_CLOUD /* FIXME: journals too */)
+                && g_atomic_int_get(&cachefile->dirty_refs) == 0)
             {
                 g_print("   ...deleting\n");
                 if (unlinkat(fs->log->dirfd, cachefile->filename, 0) < 0) {