On Mon, Jan 23, 2017 at 04:23:57PM -0800, Andrew Morton wrote:

On Sun, 22 Jan 2017 20:35:14 +0100 Sven Schmidt [off-list ref] wrote:

quoted

This patch updates LZ4 kernel module to LZ4 v1.7.3 by Yann Collet.
The kernel module is inspired by the previous work by Chanho Min.
The updated LZ4 module will not break existing code since there were alias
methods added to ensure backwards compatibility.

API changes:

New method LZ4_compress_fast which differs from the variant available
in kernel by the new acceleration parameter,
allowing to trade compression ratio for more compression speed
and vice versa.

LZ4_decompress_fast is the respective decompression method, featuring a very
fast decoder (multiple GB/s per core), able to reach RAM speed in multi-core
systems. The decompressor allows to decompress data compressed with
LZ4 fast as well as the LZ4 HC (high compression) algorithm.

Also the useful functions LZ4_decompress_safe_partial
LZ4_compress_destsize were added. The latter reverses the logic by trying to
compress as much data as possible from source to dest while the former aims
to decompress partial blocks of data.

A bunch of streaming functions were also added
which allow compressig/decompressing data in multiple steps
(so called "streaming mode").

The methods lz4_compress and lz4_decompress_unknownoutputsize
are now known as LZ4_compress_default respectivley LZ4_decompress_safe.
The old methods are still available for providing backwards compatibility.

...

+/*
+ * For backward compatibility
+ */
+static inline int lz4_compressbound(size_t isize)
 {

Do we actually need the back-compat wrappers?  After your other three
patches we have no callers, correct?  If so, we should go ahead and
eliminate such back-compatibility interfaces.

quoted

-	return isize + (isize / 255) + 16;
+	return LZ4_COMPRESSBOUND(isize);
 }

Hey Andrew,

you're absolutely right. Since I changed the callers to use the new functions, we do not need these wrappers anymore.

I will add a patch removing them and send an update.

Thanks,

Sven