From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 5 Jun 2025 20:22:55 +0000 (+0200)
Subject: journal: determine compression once, not twice
X-Git-Tag: v258-rc1~373^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b16cb30edd9b008f8d3dcacb6b6abe8009fa5315;p=thirdparty%2Fsystemd.git

journal: determine compression once, not twice

This is just paranoia: let's determine the compression to use once,
instead of twice, after all te data is in journal files which might be
corrupted any time, and it would be weird if we came to different
results here each time.
---

diff --git a/src/libsystemd/sd-journal/journal-file.c b/src/libsystemd/sd-journal/journal-file.c
index 786d757e9c0..88330dc10e0 100644
--- a/src/libsystemd/sd-journal/journal-file.c
+++ b/src/libsystemd/sd-journal/journal-file.c
@@ -1803,17 +1803,27 @@ static int journal_file_append_field(
         return 0;
 }
 
-static int maybe_compress_payload(JournalFile *f, uint8_t *dst, const uint8_t *src, uint64_t size, size_t *rsize) {
+static int maybe_compress_payload(
+                JournalFile *f,
+                uint8_t *dst,
+                const uint8_t *src,
+                uint64_t size,
+                size_t *rsize,
+                Compression *ret_compression) {
+
         assert(f);
         assert(f->header);
+        assert(ret_compression);
 
 #if HAVE_COMPRESSION
         Compression c;
         int r;
 
         c = JOURNAL_FILE_COMPRESSION(f);
-        if (c == COMPRESSION_NONE || size < f->compress_threshold_bytes)
+        if (c == COMPRESSION_NONE || size < f->compress_threshold_bytes) {
+                *ret_compression = COMPRESSION_NONE;
                 return 0;
+        }
 
         r = compress_blob(c, src, size, dst, size - 1, rsize, /* level = */ -1);
         if (r < 0)
@@ -1821,8 +1831,10 @@ static int maybe_compress_payload(JournalFile *f, uint8_t *dst, const uint8_t *s
 
         log_debug("Compressed data object %"PRIu64" -> %zu using %s", size, *rsize, compression_to_string(c));
 
+        *ret_compression = c;
         return 1; /* compressed */
 #else
+        *ret_compression = COMPRESSION_NONE;
         return 0;
 #endif
 }
@@ -1867,13 +1879,12 @@ static int journal_file_append_data(
 
         o->data.hash = htole64(hash);
 
-        r = maybe_compress_payload(f, journal_file_data_payload_field(f, o), data, size, &rsize);
+        Compression c;
+        r = maybe_compress_payload(f, journal_file_data_payload_field(f, o), data, size, &rsize, &c);
         if (r <= 0)
                 /* We don't really care failures, let's continue without compression */
                 memcpy_safe(journal_file_data_payload_field(f, o), data, size);
         else {
-                Compression c = JOURNAL_FILE_COMPRESSION(f);
-
                 assert(c >= 0 && c < _COMPRESSION_MAX && c != COMPRESSION_NONE);
 
                 o->object.size = htole64(journal_file_data_payload_offset(f) + rsize);