[PATCH 10/10] AXFS: axfs_uncompress.c

[PATCH 10/10] AXFS: axfs_uncompress.c

[Jared Hulbert]

Handles the decompression for axfs, modeled after fs/cramfs/uncompress.c.

Signed-off-by: Jared Hulbert <jaredeh@gmail.com>
---
diff --git a/fs/axfs/axfs_uncompress.c b/fs/axfs/axfs_uncompress.c
new file mode 100644
index 0000000..b7a2060
--- /dev/null
+++ b/fs/axfs/axfs_uncompress.c
@@ -0,0 +1,97 @@
+/*
+ * Advanced XIP File System for Linux - AXFS
+ *   Readonly, compressed, and XIP filesystem for Linux systems big and small
+ *
+ *   Modified in 2006 by Eric Anderson
+ *     from the cramfs sources fs/cramfs/uncompress.c
+ *
+ * (C) Copyright 1999 Linus Torvalds
+ *
+ * axfs_uncompress.c -
+ *  axfs interfaces to the uncompression library. There's really just
+ * three entrypoints:
+ *
+ *  - axfs_uncompress_init() - called to initialize the thing.
+ *  - axfs_uncompress_exit() - tell me when you're done
+ *  - axfs_uncompress_block() - uncompress a block.
+ *
+ * NOTE NOTE NOTE! The uncompression is entirely single-threaded. We
+ * only have one stream, and we'll initialize it only once even if it
+ * then is used by multiple filesystems.
+ *
+ */
+
+#include <linux/errno.h>
+#include <linux/vmalloc.h>
+#include <linux/zlib.h>
+#include <linux/mutex.h>
+
+static z_stream stream;
+static int initialized;
+static struct mutex axfs_uncmp_mutex;
+
+int axfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
+{
+	int err;
+	int out;
+
+	mutex_lock(&axfs_uncmp_mutex);
+
+	stream.next_in = src;
+	stream.avail_in = srclen;
+
+	stream.next_out = dst;
+	stream.avail_out = dstlen;
+
+	err = zlib_inflateReset(&stream);
+	if (err != Z_OK) {
+		printk(KERN_ERR "zlib_inflateReset error %d\n", err);
+		zlib_inflateEnd(&stream);
+		zlib_inflateInit(&stream);
+	}
+
+	err = zlib_inflate(&stream, Z_FINISH);
+	if (err != Z_STREAM_END)
+		goto err;
+
+	out = stream.total_out;
+
+	mutex_unlock(&axfs_uncmp_mutex);
+
+	return out;
+
+err:
+
+	mutex_unlock(&axfs_uncmp_mutex);
+
+	printk(KERN_ERR "Error %d while decompressing!\n", err);
+	printk(KERN_ERR "%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
+	return 0;
+}
+
+int axfs_uncompress_init(void)
+{
+	if (!initialized++) {
+
+		mutex_init(&axfs_uncmp_mutex);
+
+		stream.workspace = vmalloc(zlib_inflate_workspacesize());
+		if (!stream.workspace) {
+			initialized = 0;
+			return -ENOMEM;
+		}
+		stream.next_in = NULL;
+		stream.avail_in = 0;
+		zlib_inflateInit(&stream);
+	}
+	return 0;
+}
+
+int axfs_uncompress_exit(void)
+{
+	if (!--initialized) {
+		zlib_inflateEnd(&stream);
+		vfree(stream.workspace);
+	}
+	return 0;
+}

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Sven Wegener]

On Wed, 20 Aug 2008, Jared Hulbert wrote:

> Handles the decompression for axfs, modeled after fs/cramfs/uncompress.c.
> 
> Signed-off-by: Jared Hulbert <jaredeh@gmail.com>
> ---
> diff --git a/fs/axfs/axfs_uncompress.c b/fs/axfs/axfs_uncompress.c
> new file mode 100644
> index 0000000..b7a2060
> --- /dev/null
> +++ b/fs/axfs/axfs_uncompress.c
> @@ -0,0 +1,97 @@
> +/*
> + * Advanced XIP File System for Linux - AXFS
> + *   Readonly, compressed, and XIP filesystem for Linux systems big and small
> + *
> + *   Modified in 2006 by Eric Anderson
> + *     from the cramfs sources fs/cramfs/uncompress.c
> + *
> + * (C) Copyright 1999 Linus Torvalds
> + *
> + * axfs_uncompress.c -
> + *  axfs interfaces to the uncompression library. There's really just
> + * three entrypoints:
> + *
> + *  - axfs_uncompress_init() - called to initialize the thing.
> + *  - axfs_uncompress_exit() - tell me when you're done
> + *  - axfs_uncompress_block() - uncompress a block.
> + *
> + * NOTE NOTE NOTE! The uncompression is entirely single-threaded. We
> + * only have one stream, and we'll initialize it only once even if it
> + * then is used by multiple filesystems.
> + *
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/vmalloc.h>
> +#include <linux/zlib.h>
> +#include <linux/mutex.h>
> +
> +static z_stream stream;
> +static int initialized;
> +static struct mutex axfs_uncmp_mutex;

Use DEFINE_MUTEX and drop the mutex_init() down in the init function.

> +
> +int axfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
> +{
> +	int err;
> +	int out;
> +
> +	mutex_lock(&axfs_uncmp_mutex);
> +
> +	stream.next_in = src;
> +	stream.avail_in = srclen;
> +
> +	stream.next_out = dst;
> +	stream.avail_out = dstlen;
> +
> +	err = zlib_inflateReset(&stream);
> +	if (err != Z_OK) {
> +		printk(KERN_ERR "zlib_inflateReset error %d\n", err);
> +		zlib_inflateEnd(&stream);
> +		zlib_inflateInit(&stream);
> +	}
> +
> +	err = zlib_inflate(&stream, Z_FINISH);
> +	if (err != Z_STREAM_END)
> +		goto err;
> +
> +	out = stream.total_out;
> +
> +	mutex_unlock(&axfs_uncmp_mutex);
> +
> +	return out;
> +
> +err:
> +
> +	mutex_unlock(&axfs_uncmp_mutex);
> +
> +	printk(KERN_ERR "Error %d while decompressing!\n", err);
> +	printk(KERN_ERR "%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
> +	return 0;
> +}
> +
> +int axfs_uncompress_init(void)
> +{
> +	if (!initialized++) {
> +
> +		mutex_init(&axfs_uncmp_mutex);
> +
> +		stream.workspace = vmalloc(zlib_inflate_workspacesize());
> +		if (!stream.workspace) {
> +			initialized = 0;
> +			return -ENOMEM;
> +		}
> +		stream.next_in = NULL;
> +		stream.avail_in = 0;
> +		zlib_inflateInit(&stream);
> +	}
> +	return 0;
> +}
> +
> +int axfs_uncompress_exit(void)
> +{
> +	if (!--initialized) {
> +		zlib_inflateEnd(&stream);
> +		vfree(stream.workspace);
> +	}
> +	return 0;
> +}

axfs_uncompress_init() and axfs_uncompress_exit() are only called during 
init and exit of the module, no need for the initialized variable and the 
functions can be annotated with __init and __exit.

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Artem Bityutskiy]

On Wed, 2008-08-20 at 22:46 -0700, Jared Hulbert wrote:
> +	err = zlib_inflateReset(&stream);
> +	if (err != Z_OK) {
> +		printk(KERN_ERR "zlib_inflateReset error %d\n", err);
> +		zlib_inflateEnd(&stream);
> +		zlib_inflateInit(&stream);
> +	}

Jared,

just FYI, are you aware that LZO which is also present in the kernel is
much faster on decompress than zlib, while its compression is only
slightly worse?

I do not remember the digits, but last time I tested UBIFS, LZO
decompression was about 3 times faster than zlib on OMAP3. This depends
on architecture, etc of course. This may matter a lot if one is fighting
for faster system boot-up. So you might consider supporting LZO as well.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Geert Uytterhoeven]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1417 bytes --]

On Thu, 21 Aug 2008, Artem Bityutskiy wrote:
> On Wed, 2008-08-20 at 22:46 -0700, Jared Hulbert wrote:
> > +	err = zlib_inflateReset(&stream);
> > +	if (err != Z_OK) {
> > +		printk(KERN_ERR "zlib_inflateReset error %d\n", err);
> > +		zlib_inflateEnd(&stream);
> > +		zlib_inflateInit(&stream);
> > +	}
> 
> just FYI, are you aware that LZO which is also present in the kernel is
> much faster on decompress than zlib, while its compression is only
> slightly worse?

If you want support for multiple decompression algorithms, you can switch
from using zlib_inflate*() directly to calling zlib through the crypto API.
Then you can call crypto_alloc_comp() with the correct decompression algorithm
name.

For squashfs, I had to modify only ca. 40 lines of code.

You do need a new zlib crypto module, as the existing deflate crypto module
uses the raw deflate format instead of the zlib format, and has some parameters
tuned for its use in IPSec.

I hope to have some patches ready next week...

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
Fax:      +32 (0)2 700 8622
E-mail:   Geert.Uytterhoeven@sonycom.com
Internet: http://www.sony-europe.com/

A division of Sony Europe (Belgium) N.V.
VAT BE 0413.825.160 · RPR Brussels
Fortis · BIC GEBABEBB · IBAN BE41293037680010

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Jared Hulbert]

> If you want support for multiple decompression algorithms, you can switch
> from using zlib_inflate*() directly to calling zlib through the crypto API.
> Then you can call crypto_alloc_comp() with the correct decompression algorithm
> name.
>
> For squashfs, I had to modify only ca. 40 lines of code.

I definately want to support multiple formats.  I have a flag in the
superblock all ready to go for that.  One problem.  I'm not sure how
to do it.  Can you point us to some reference code?

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Jared Hulbert]

> Use DEFINE_MUTEX and drop the mutex_init() down in the init function.

okay.  by drop you mean delete?

> axfs_uncompress_init() and axfs_uncompress_exit() are only called during
> init and exit of the module, no need for the initialized variable and the
> functions can be annotated with __init and __exit.

can be annotated or should be?

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Sven Wegener]

On Thu, 21 Aug 2008, Jared Hulbert wrote:

> > Use DEFINE_MUTEX and drop the mutex_init() down in the init function.
> 
> okay.  by drop you mean delete?

Yes.

> > axfs_uncompress_init() and axfs_uncompress_exit() are only called during
> > init and exit of the module, no need for the initialized variable and the
> > functions can be annotated with __init and __exit.
> 
> can be annotated or should be?

Should be. We only need them once during init and cleanup. If you want to 
call axfs_uncompress_exit() from init_axfs_fs() to clean up in case of 
register_filesystem failing, you can't annotate axfs_uncompress_exit() 
with __exit.

Sven

Re: [PATCH 10/10] AXFS: axfs_uncompress.c

[Geert Uytterhoeven]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1113 bytes --]

	Hi Jared,

On Thu, 21 Aug 2008, Jared Hulbert wrote:
> > If you want support for multiple decompression algorithms, you can switch
> > from using zlib_inflate*() directly to calling zlib through the crypto API.
> > Then you can call crypto_alloc_comp() with the correct decompression algorithm
> > name.
> >
> > For squashfs, I had to modify only ca. 40 lines of code.
> 
> I definately want to support multiple formats.  I have a flag in the
> superblock all ready to go for that.  One problem.  I'm not sure how
> to do it.  Can you point us to some reference code?

Please take a look at the email with subject

    [patch 3/3] squashfs: Switch from zlib/inflate to "zlib" crypto module

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
Fax:      +32 (0)2 700 8622
E-mail:   Geert.Uytterhoeven@sonycom.com
Internet: http://www.sony-europe.com/

A division of Sony Europe (Belgium) N.V.
VAT BE 0413.825.160 · RPR Brussels
Fortis · BIC GEBABEBB · IBAN BE41293037680010