squashfs: Add zstd support
authorSean Purcell <me@seanp.xyz>
Thu, 10 Aug 2017 02:42:36 +0000 (19:42 -0700)
committerChris Mason <clm@fb.com>
Sat, 9 Sep 2017 02:33:25 +0000 (19:33 -0700)
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
fs/squashfs/Makefile
fs/squashfs/decompressor.c
fs/squashfs/decompressor.h
fs/squashfs/squashfs_fs.h
fs/squashfs/zstd_wrapper.c [new file with mode: 0644]

index ffb093e72b6ca89a0f8d339dfad3f04da0c97e8e..1adb3346b9d6aa659cf5aaf5f82afe1d81a8118f 100644 (file)
@@ -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
index 246a6f329d8957df4b3bf48129b3f0e415be2611..6655631c53ae78573c3f88d14d6f60d134ed1639 100644 (file)
@@ -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
index d2bc13636f7927a7485bb153c4d0883a7b2ea1e2..836639810ea01720982176ddd1aeb22d7e40835a 100644 (file)
@@ -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
 };
 
index a25713c031a51213edc9dd5a32de73f64f75c44f..0f5a8e4e58dae999fae44f95e232738cf0bebe7c 100644 (file)
@@ -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
index 506f4ba5b98309b9041cc99103312837b2724e58..24d12fd1417767689778302abf77b21f1efd6350 100644 (file)
@@ -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;
diff --git a/fs/squashfs/zstd_wrapper.c b/fs/squashfs/zstd_wrapper.c
new file mode 100644 (file)
index 0000000..eeaabf8
--- /dev/null
@@ -0,0 +1,151 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * zstd_wrapper.c
+ */
+
+#include <linux/mutex.h>
+#include <linux/buffer_head.h>
+#include <linux/slab.h>
+#include <linux/zstd.h>
+#include <linux/vmalloc.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+struct workspace {
+       void *mem;
+       size_t mem_size;
+       size_t window_size;
+};
+
+static void *zstd_init(struct squashfs_sb_info *msblk, void *buff)
+{
+       struct workspace *wksp = kmalloc(sizeof(*wksp), GFP_KERNEL);
+
+       if (wksp == NULL)
+               goto failed;
+       wksp->window_size = max_t(size_t,
+                       msblk->block_size, SQUASHFS_METADATA_SIZE);
+       wksp->mem_size = ZSTD_DStreamWorkspaceBound(wksp->window_size);
+       wksp->mem = vmalloc(wksp->mem_size);
+       if (wksp->mem == NULL)
+               goto failed;
+
+       return wksp;
+
+failed:
+       ERROR("Failed to allocate zstd workspace\n");
+       kfree(wksp);
+       return ERR_PTR(-ENOMEM);
+}
+
+
+static void zstd_free(void *strm)
+{
+       struct workspace *wksp = strm;
+
+       if (wksp)
+               vfree(wksp->mem);
+       kfree(wksp);
+}
+
+
+static int zstd_uncompress(struct squashfs_sb_info *msblk, void *strm,
+       struct buffer_head **bh, int b, int offset, int length,
+       struct squashfs_page_actor *output)
+{
+       struct workspace *wksp = strm;
+       ZSTD_DStream *stream;
+       size_t total_out = 0;
+       size_t zstd_err;
+       int k = 0;
+       ZSTD_inBuffer in_buf = { NULL, 0, 0 };
+       ZSTD_outBuffer out_buf = { NULL, 0, 0 };
+
+       stream = ZSTD_initDStream(wksp->window_size, wksp->mem, wksp->mem_size);
+
+       if (!stream) {
+               ERROR("Failed to initialize zstd decompressor\n");
+               goto out;
+       }
+
+       out_buf.size = PAGE_SIZE;
+       out_buf.dst = squashfs_first_page(output);
+
+       do {
+               if (in_buf.pos == in_buf.size && k < b) {
+                       int avail = min(length, msblk->devblksize - offset);
+
+                       length -= avail;
+                       in_buf.src = bh[k]->b_data + offset;
+                       in_buf.size = avail;
+                       in_buf.pos = 0;
+                       offset = 0;
+               }
+
+               if (out_buf.pos == out_buf.size) {
+                       out_buf.dst = squashfs_next_page(output);
+                       if (out_buf.dst == NULL) {
+                               /* Shouldn't run out of pages
+                                * before stream is done.
+                                */
+                               squashfs_finish_page(output);
+                               goto out;
+                       }
+                       out_buf.pos = 0;
+                       out_buf.size = PAGE_SIZE;
+               }
+
+               total_out -= out_buf.pos;
+               zstd_err = ZSTD_decompressStream(stream, &out_buf, &in_buf);
+               total_out += out_buf.pos; /* add the additional data produced */
+
+               if (in_buf.pos == in_buf.size && k < b)
+                       put_bh(bh[k++]);
+       } while (zstd_err != 0 && !ZSTD_isError(zstd_err));
+
+       squashfs_finish_page(output);
+
+       if (ZSTD_isError(zstd_err)) {
+               ERROR("zstd decompression error: %d\n",
+                               (int)ZSTD_getErrorCode(zstd_err));
+               goto out;
+       }
+
+       if (k < b)
+               goto out;
+
+       return (int)total_out;
+
+out:
+       for (; k < b; k++)
+               put_bh(bh[k]);
+
+       return -EIO;
+}
+
+const struct squashfs_decompressor squashfs_zstd_comp_ops = {
+       .init = zstd_init,
+       .free = zstd_free,
+       .decompress = zstd_uncompress,
+       .id = ZSTD_COMPRESSION,
+       .name = "zstd",
+       .supported = 1
+};