[systemd-devel] [PATCH] journal/compress: use LZ4_compress_continue()

[Evangelos Foutras]

We can't use LZ4_compress_limitedOutput_continue() because in the
worst-case scenario the compressed output can be slightly bigger than
the input block. This generally affects very few blocks and is no reason
to abort the compression process.

I ran into this when I noticed that Chromium core dumps weren't being
compressed. After switching to LZ4_compress_continue() a ~330MB Chromium
core dump gets compressed to ~17M.
---
 src/journal/compress.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/journal/compress.c b/src/journal/compress.c
index 52a4c10..c4c715b 100644
--- a/src/journal/compress.c
+++ b/src/journal/compress.c
@@ -460,10 +460,10 @@ int compress_stream_lz4(int fdf, int fdt, off_t max_bytes) {
 
                 total_in += n;
 
-                r = LZ4_compress_limitedOutput_continue(&lz4_data, buf, out, n, n);
+                r = LZ4_compress_continue(&lz4_data, buf, out, n);
                 if (r == 0) {
-                        log_debug("Compressed size exceeds original, aborting compression.");
-                        return -ENOBUFS;
+                        log_error("LZ4 compression failed.");
+                        return -EBADMSG;
                 }
 
                 header = htole32(r);
-- 
2.1.0