Bugfix in partial log fetching.

Do not bother mapping the file until the data is available, otherwise the
mapping may be deleted from under us while we are waiting.

diff --git a/bluesky/log.c b/bluesky/log.c
index 88b95df..d9ad11b 100644 (file)
--- a/bluesky/log.c
+++ b/bluesky/log.c
@@ -581,26 +581,6 @@ BlueSkyRCStr *bluesky_log_map_object(BlueSkyCloudLog *item, gboolean map_data)
         file_size = item->location.size;
     }
 
-    if (map->addr == NULL) {
-        int fd = openat(log->dirfd, map->filename, O_RDONLY);
-
-        if (fd < 0) {
-            fprintf(stderr, "Error opening logfile %s: %m\n", map->filename);
-            goto exit2;
-        }
-
-        off_t length = lseek(fd, 0, SEEK_END);
-        map->addr = (const char *)mmap(NULL, length, PROT_READ, MAP_SHARED,
-                                       fd, 0);
-        g_atomic_int_add(&log->disk_used, -(map->len / 1024));
-        map->len = length;
-        g_atomic_int_add(&log->disk_used, map->len / 1024);
-
-        g_atomic_int_inc(&map->refcount);
-
-        close(fd);
-    }
-
     /* Log segments fetched from the cloud might only be partially-fetched.
      * Check whether the object we are interested in is available. */
     if (location == CLOUDLOG_CLOUD) {
@@ -627,6 +607,26 @@ BlueSkyRCStr *bluesky_log_map_object(BlueSkyCloudLog *item, gboolean map_data)
         }
     }
 
+    if (map->addr == NULL) {
+        int fd = openat(log->dirfd, map->filename, O_RDONLY);
+
+        if (fd < 0) {
+            fprintf(stderr, "Error opening logfile %s: %m\n", map->filename);
+            goto exit2;
+        }
+
+        off_t length = lseek(fd, 0, SEEK_END);
+        map->addr = (const char *)mmap(NULL, length, PROT_READ, MAP_SHARED,
+                                       fd, 0);
+        g_atomic_int_add(&log->disk_used, -(map->len / 1024));
+        map->len = length;
+        g_atomic_int_add(&log->disk_used, map->len / 1024);
+
+        g_atomic_int_inc(&map->refcount);
+
+        close(fd);
+    }
+
     if (map_data) {
         if (location == CLOUDLOG_JOURNAL)
             file_offset += sizeof(struct log_header);