linux-kernel - Re: [PATCH 10/10] AXFS: axfs

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Message-ID: <alpine.LNX.1.10.0808211028150.12259@titan.stealer.net>
Date:	Thu, 21 Aug 2008 11:01:53 +0200 (CEST)
From:	Sven Wegener <sven.wegener@...aler.net>
To:	Jared Hulbert <jaredeh@...il.com>
cc:	Linux-kernel@...r.kernel.org, linux-embedded@...r.kernel.org,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	Jörn Engel <joern@...fs.org>,
	tim.bird@...SONY.COM, cotte@...ibm.com, nickpiggin@...oo.com.au
Subject: Re: [PATCH 10/10] AXFS: axfs_uncompress.c

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@...il.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.
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