[v4,4/5] squashfs: Add zstd support
diff mbox

Message ID 20170804201921.156890-5-terrelln@fb.com
State New
Headers show

Commit Message

Nick Terrell Aug. 4, 2017, 8:19 p.m. UTC
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

Cc: Sean Purcell <me@seanp.xyz>
Signed-off-by: Nick Terrell <terrelln@fb.com>
---
v3 -> v4:
- Fix minor linter warnings

 fs/squashfs/Kconfig        |  14 +++++
 fs/squashfs/Makefile       |   1 +
 fs/squashfs/decompressor.c |   7 +++
 fs/squashfs/decompressor.h |   4 ++
 fs/squashfs/squashfs_fs.h  |   1 +
 fs/squashfs/zstd_wrapper.c | 149 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 176 insertions(+)
 create mode 100644 fs/squashfs/zstd_wrapper.c

--
2.9.3
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Comments

Linus Torvalds Aug. 4, 2017, 10:10 p.m. UTC | #1
On Fri, Aug 4, 2017 at 1:19 PM, Nick Terrell <terrelln@fb.com> wrote:
>
> This patch was written by Sean Purcell <me@seanp.xyz>, but I will be
> taking over the submission process.

Please, if so, get Sean's sign-off, and also make sure that the patch
gets submitted with

   From: Sean Purcell <me@seanp.xyz>

at the top of the body of the email so that authorship gets properly
attributed by all the usual tools.

             Linus
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Nick Terrell Aug. 4, 2017, 10:32 p.m. UTC | #2
On 8/4/17, 3:10 PM, "linus971@gmail.com on behalf of Linus Torvalds" <linus971@gmail.com on behalf of torvalds@linux-foundation.org> wrote:
> On Fri, Aug 4, 2017 at 1:19 PM, Nick Terrell <terrelln@fb.com> wrote:

> >

> > This patch was written by Sean Purcell <me@seanp.xyz>, but I will be

> > taking over the submission process.

> 

> Please, if so, get Sean's sign-off, and also make sure that the patch

> gets submitted with

> 

>    From: Sean Purcell <me@seanp.xyz>

> 

> at the top of the body of the email so that authorship gets properly

> attributed by all the usual tools.

> 

>              Linus

> 


Thanks for the help, I'll fix it for the next version.
Sean Purcell Aug. 4, 2017, 11:39 p.m. UTC | #3
Signed-off-by: Sean Purcell <me@seanp.xyz>

On Fri, Aug 4, 2017 at 4:19 PM, Nick Terrell <terrelln@fb.com> wrote:
> 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
>
> Cc: Sean Purcell <me@seanp.xyz>
> Signed-off-by: Nick Terrell <terrelln@fb.com>
> ---
> v3 -> v4:
> - Fix minor linter warnings
>
>  fs/squashfs/Kconfig        |  14 +++++
>  fs/squashfs/Makefile       |   1 +
>  fs/squashfs/decompressor.c |   7 +++
>  fs/squashfs/decompressor.h |   4 ++
>  fs/squashfs/squashfs_fs.h  |   1 +
>  fs/squashfs/zstd_wrapper.c | 149 +++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 176 insertions(+)
>  create mode 100644 fs/squashfs/zstd_wrapper.c
>
> diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
> index ffb093e..1adb334 100644
> --- a/fs/squashfs/Kconfig
> +++ b/fs/squashfs/Kconfig
> @@ -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
> diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
> index 246a6f3..6655631 100644
> --- a/fs/squashfs/Makefile
> +++ b/fs/squashfs/Makefile
> @@ -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
> diff --git a/fs/squashfs/decompressor.c b/fs/squashfs/decompressor.c
> index d2bc136..8366398 100644
> --- a/fs/squashfs/decompressor.c
> +++ b/fs/squashfs/decompressor.c
> @@ -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
>  };
>
> diff --git a/fs/squashfs/decompressor.h b/fs/squashfs/decompressor.h
> index a25713c..0f5a8e4 100644
> --- a/fs/squashfs/decompressor.h
> +++ b/fs/squashfs/decompressor.h
> @@ -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
> diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
> index 506f4ba..24d12fd 100644
> --- a/fs/squashfs/squashfs_fs.h
> +++ b/fs/squashfs/squashfs_fs.h
> @@ -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
> index 0000000..d70efa8
> --- /dev/null
> +++ b/fs/squashfs/zstd_wrapper.c
> @@ -0,0 +1,149 @@
> +/*
> + * 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;
> +};
> +
> +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->mem_size = ZSTD_DStreamWorkspaceBound(max_t(size_t,
> +                               msblk->block_size, SQUASHFS_METADATA_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->mem_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
> +};
> --
> 2.9.3
>

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Geert Uytterhoeven Aug. 13, 2017, 8:31 a.m. UTC | #4
On Fri, Aug 4, 2017 at 10:19 PM, Nick Terrell <terrelln@fb.com> wrote:
> --- a/fs/squashfs/decompressor.c
> +++ b/fs/squashfs/decompressor.c
> @@ -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

Can you please use designated initializers?

> +};
> +#endif
> +
>  static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
>         NULL, NULL, NULL, NULL, 0, "unknown", 0
> ;

> +const struct squashfs_decompressor squashfs_zstd_comp_ops = {
> +       .init = zstd_init,
> +       .free = zstd_free,
> +       .decompress = zstd_uncompress,
> +       .id = ZSTD_COMPRESSION,
> +       .name = "zstd",
> +       .supported = 1
> +};

... like you did here.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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Phillip Lougher Aug. 14, 2017, 2:23 a.m. UTC | #5
On Sun, Aug 13, 2017 at 9:31 AM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> On Fri, Aug 4, 2017 at 10:19 PM, Nick Terrell <terrelln@fb.com> wrote:
>> --- a/fs/squashfs/decompressor.c
>> +++ b/fs/squashfs/decompressor.c
>> @@ -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
>
> Can you please use designated initializers?

I prefer it as it is.  It matches the coding style that I used in the
rest of that file to declare the "unsupported" compressor entries (if
this patch uses a different style it would look odd).    There's no
pointers to functions being assigned here, and it makes it a short and
concise one-line.

Phillip

>
>> +};
>> +#endif
>> +
>>  static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
>>         NULL, NULL, NULL, NULL, 0, "unknown", 0
>> ;
>
>> +const struct squashfs_decompressor squashfs_zstd_comp_ops = {
>> +       .init = zstd_init,
>> +       .free = zstd_free,
>> +       .decompress = zstd_uncompress,
>> +       .id = ZSTD_COMPRESSION,
>> +       .name = "zstd",
>> +       .supported = 1
>> +};
>
> ... like you did here.
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
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Patch
diff mbox

diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index ffb093e..1adb334 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -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
diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
index 246a6f3..6655631 100644
--- a/fs/squashfs/Makefile
+++ b/fs/squashfs/Makefile
@@ -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
diff --git a/fs/squashfs/decompressor.c b/fs/squashfs/decompressor.c
index d2bc136..8366398 100644
--- a/fs/squashfs/decompressor.c
+++ b/fs/squashfs/decompressor.c
@@ -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
 };

diff --git a/fs/squashfs/decompressor.h b/fs/squashfs/decompressor.h
index a25713c..0f5a8e4 100644
--- a/fs/squashfs/decompressor.h
+++ b/fs/squashfs/decompressor.h
@@ -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
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 506f4ba..24d12fd 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -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
index 0000000..d70efa8
--- /dev/null
+++ b/fs/squashfs/zstd_wrapper.c
@@ -0,0 +1,149 @@ 
+/*
+ * 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;
+};
+
+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->mem_size = ZSTD_DStreamWorkspaceBound(max_t(size_t,
+				msblk->block_size, SQUASHFS_METADATA_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->mem_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
+};