squashfs: Add zstd support (87bf54bb) · Commits · 戴 / test

Add zstd compression and decompression support to SquashFS. zstd is a great fit for SquashFS because it can compress at ratios approaching xz, while decompressing twice as fast as zlib. For SquashFS in particular, it can decompress as fast as lzo and lz4. It also has the flexibility to turn down the compression ratio for faster compression times. The compression benchmark is run on the file tree from the SquashFS archive found in ubuntu-16.10-desktop-amd64.iso [1]. It uses `mksquashfs` with the default block size (128 KB) and and various compression algorithms/levels. xz and zstd are also benchmarked with 256 KB blocks. The decompression benchmark times how long it takes to `tar` the file tree into `/dev/null`. See the benchmark file in the upstream zstd source repository located under `contrib/linux-kernel/squashfs-benchmark.sh` [2] for details. I ran the benchmarks on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM. The VM is running on a MacBook Pro with a 3.1 GHz Intel Core i7 processor, 16 GB of RAM, and a SSD. | Method | Ratio | Compression MB/s | Decompression MB/s | |----------------|-------|------------------|--------------------| | gzip | 2.92 | 15 | 128 | | lzo | 2.64 | 9.5 | 217 | | lz4 | 2.12 | 94 | 218 | | xz | 3.43 | 5.5 | 35 | | xz 256 KB | 3.53 | 5.4 | 40 | | zstd 1 | 2.71 | 96 | 210 | | zstd 5 | 2.93 | 69 | 198 | | zstd 10 | 3.01 | 41 | 225 | | zstd 15 | 3.13 | 11.4 | 224 | | zstd 16 256 KB | 3.24 | 8.1 | 210 | This patch was written by Sean Purcell <me@seanp.xyz>, but I will be taking over the submission process. [1] http://releases.ubuntu.com/16.10/ [2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/squashfs-benchmark.sh zstd source repository: https://github.com/facebook/zstd Signed-off-by:

Sean Purcell <me@seanp.xyz> Signed-off-by:

Nick Terrell <terrelln@fb.com> Signed-off-by:

Chris Mason <clm@fb.com> Acked-by:

Phillip Lougher <phillip@squashfs.org.uk>

fs/squashfs/Kconfig

+14 −0

Original line number	Diff line number	Diff line
		@@ -165,6 +165,20 @@ config SQUASHFS_XZ

		If unsure, say N.

		config SQUASHFS_ZSTD
		bool "Include support for ZSTD compressed file systems"
		depends on SQUASHFS
		select ZSTD_DECOMPRESS
		help
		Saying Y here includes support for reading Squashfs file systems
		compressed with ZSTD compression. ZSTD gives better compression than
		the default ZLIB compression, while using less CPU.

		ZSTD is not the standard compression used in Squashfs and so most
		file systems will be readable without selecting this option.

		If unsure, say N.

		config SQUASHFS_4K_DEVBLK_SIZE
		bool "Use 4K device block size?"
		depends on SQUASHFS

fs/squashfs/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -15,3 +15,4 @@ squashfs-$(CONFIG_SQUASHFS_LZ4) += lz4_wrapper.o
		squashfs-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o
		squashfs-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o
		squashfs-$(CONFIG_SQUASHFS_ZLIB) += zlib_wrapper.o
		squashfs-$(CONFIG_SQUASHFS_ZSTD) += zstd_wrapper.o

fs/squashfs/decompressor.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -65,6 +65,12 @@ static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
		};
		#endif

		#ifndef CONFIG_SQUASHFS_ZSTD
		static const struct squashfs_decompressor squashfs_zstd_comp_ops = {
		NULL, NULL, NULL, NULL, ZSTD_COMPRESSION, "zstd", 0
		};
		#endif

		static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
		NULL, NULL, NULL, NULL, 0, "unknown", 0
		};
		@@ -75,6 +81,7 @@ static const struct squashfs_decompressor *decompressor[] = {
		&squashfs_lzo_comp_ops,
		&squashfs_xz_comp_ops,
		&squashfs_lzma_unsupported_comp_ops,
		&squashfs_zstd_comp_ops,
		&squashfs_unknown_comp_ops
		};

fs/squashfs/decompressor.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -58,4 +58,8 @@ extern const struct squashfs_decompressor squashfs_lzo_comp_ops;
		extern const struct squashfs_decompressor squashfs_zlib_comp_ops;
		#endif

		#ifdef CONFIG_SQUASHFS_ZSTD
		extern const struct squashfs_decompressor squashfs_zstd_comp_ops;
		#endif

		#endif

fs/squashfs/squashfs_fs.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -241,6 +241,7 @@ struct meta_index {
		#define LZO_COMPRESSION 3
		#define XZ_COMPRESSION 4
		#define LZ4_COMPRESSION 5
		#define ZSTD_COMPRESSION 6

		struct squashfs_super_block {
		__le32 s_magic;

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