journal: fix error handling when compressing journal objects

Let's make sure we handle compression errors properly, and don't
misunderstand an error for success.

Also, let's actually compress things if lz4 is enabled.

Fixes #1662.

2 files changed, 11 insertions, 5 deletions

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index 1071c6d6d7..89068f26d2 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -1076,23 +1076,24 @@ static int journal_file_append_data(
         o->data.hash = htole64(hash);
 
 #if defined(HAVE_XZ) || defined(HAVE_LZ4)
-        if (f->compress_xz &&
-            size >= COMPRESSION_SIZE_THRESHOLD) {
+        if (JOURNAL_FILE_COMPRESS(f) && size >= COMPRESSION_SIZE_THRESHOLD) {
                 size_t rsize = 0;
 
                 compression = compress_blob(data, size, o->data.payload, &rsize);
 
-                if (compression) {
+                if (compression >= 0) {
                         o->object.size = htole64(offsetof(Object, data.payload) + rsize);
                         o->object.flags |= compression;
 
                         log_debug("Compressed data object %"PRIu64" -> %zu using %s",
                                   size, rsize, object_compressed_to_string(compression));
-                }
+                } else
+                        /* Compression didn't work, we don't really care why, let's continue without compression */
+                        compression = 0;
         }
 #endif
 
-        if (!compression && size > 0)
+        if (compression == 0 && size > 0)
                 memcpy(o->data.payload, data, size);
 
         r = journal_file_link_data(f, o, p, hash);
diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
index f2c07356c8..898d12d992 100644
--- a/src/journal/journal-file.h
+++ b/src/journal/journal-file.h
@@ -235,3 +235,8 @@ bool journal_file_rotate_suggested(JournalFile *f, usec_t max_file_usec);
 
 int journal_file_map_data_hash_table(JournalFile *f);
 int journal_file_map_field_hash_table(JournalFile *f);
+
+static inline bool JOURNAL_FILE_COMPRESS(JournalFile *f) {
+        assert(f);
+        return f->compress_xz || f->compress_lz4;
+}