Commit 9508c6b9 authored by Phillip Lougher's avatar Phillip Lougher
Browse files

Squashfs: Refactor decompressor interface and code 



The decompressor interface and code was written from
the point of view of single-threaded operation.  In doing
so it mixed a lot of single-threaded implementation specific
aspects into the decompressor code and elsewhere which makes it
difficult to seamlessly support multiple different decompressor
implementations.

This patch does the following:

1.  It removes compressor_options parsing from the decompressor
    init() function.  This allows the decompressor init() function
    to be dynamically called to instantiate multiple decompressors,
    without the compressor options needing to be read and parsed each
    time.

2.  It moves threading and all sleeping operations out of the
    decompressors.  In doing so, it makes the decompressors
    non-blocking wrappers which only deal with interfacing with
    the decompressor implementation.

3. It splits decompressor.[ch] into decompressor generic functions
   in decompressor.[ch], and moves the single threaded
   decompressor implementation into decompressor_single.c.

The result of this patch is Squashfs should now be able to
support multiple decompressors by adding new decompressor_xxx.c
files with specialised implementations of the functions in
decompressor_single.c

Signed-off-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
parent 959f5854

fs/squashfs/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 


obj-$(CONFIG_SQUASHFS) += squashfs.o

squashfs-y += block.o cache.o dir.o export.o file.o fragment.o id.o inode.o

squashfs-y += namei.o super.o symlink.o decompressor.o

squashfs-y += namei.o super.o symlink.o decompressor.o decompressor_single.o

squashfs-$(CONFIG_SQUASHFS_XATTR) += xattr.o xattr_id.o

squashfs-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o

squashfs-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o

fs/squashfs/block.c

+7 −4
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, 
	struct buffer_head **bh;

	int offset = index & ((1 << msblk->devblksize_log2) - 1);

	u64 cur_index = index >> msblk->devblksize_log2;

	int bytes, compressed, b = 0, k = 0, page = 0, avail;

	int bytes, compressed, b = 0, k = 0, page = 0, avail, i;



	bh = kcalloc(((srclength + msblk->devblksize - 1)

		>> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
@@ -158,6 +158,12 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, 
		ll_rw_block(READ, b - 1, bh + 1);

	}



	for (i = 0; i < b; i++) {

		wait_on_buffer(bh[i]);

		if (!buffer_uptodate(bh[i]))

			goto block_release;

	}



	if (compressed) {

		length = squashfs_decompress(msblk, buffer, bh, b, offset,

			 length, srclength, pages);
@@ -172,9 +178,6 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, 
		for (bytes = length; k < b; k++) {

			in = min(bytes, msblk->devblksize - offset);

			bytes -= in;

			wait_on_buffer(bh[k]);

			if (!buffer_uptodate(bh[k]))

				goto block_release;

			while (in) {

				if (pg_offset == PAGE_CACHE_SIZE) {

					page++;

fs/squashfs/decompressor.c

+32 −15
Original line number Diff line number Diff line
@@ -37,29 +37,29 @@ 
 */



static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = {

	NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0

	NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0

};



#ifndef CONFIG_SQUASHFS_LZO

static const struct squashfs_decompressor squashfs_lzo_comp_ops = {

	NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0

	NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0

};

#endif



#ifndef CONFIG_SQUASHFS_XZ

static const struct squashfs_decompressor squashfs_xz_comp_ops = {

	NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0

	NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0

};

#endif



#ifndef CONFIG_SQUASHFS_ZLIB

static const struct squashfs_decompressor squashfs_zlib_comp_ops = {

	NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0

	NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0

};

#endif



static const struct squashfs_decompressor squashfs_unknown_comp_ops = {

	NULL, NULL, NULL, 0, "unknown", 0

	NULL, NULL, NULL, NULL, 0, "unknown", 0

};



static const struct squashfs_decompressor *decompressor[] = {
@@ -83,10 +83,10 @@ const struct squashfs_decompressor *squashfs_lookup_decompressor(int id) 
}





void *squashfs_decompressor_init(struct super_block *sb, unsigned short flags)

static void *get_comp_opts(struct super_block *sb, unsigned short flags)

{

	struct squashfs_sb_info *msblk = sb->s_fs_info;

	void *strm, *buffer = NULL;

	void *buffer = NULL, *comp_opts;

	int length = 0;



	/*
@@ -94,23 +94,40 @@ void *squashfs_decompressor_init(struct super_block *sb, unsigned short flags) 
	 */

	if (SQUASHFS_COMP_OPTS(flags)) {

		buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);

		if (buffer == NULL)

			return ERR_PTR(-ENOMEM);

		if (buffer == NULL) {

			comp_opts = ERR_PTR(-ENOMEM);

			goto out;

		}



		length = squashfs_read_data(sb, &buffer,

			sizeof(struct squashfs_super_block), 0, NULL,

				PAGE_CACHE_SIZE, 1);



		if (length < 0) {

			strm = ERR_PTR(length);

			goto finished;

			comp_opts = ERR_PTR(length);

			goto out;

		}

	}



	strm = msblk->decompressor->init(msblk, buffer, length);

	comp_opts = squashfs_comp_opts(msblk, buffer, length);



finished:

out:

	kfree(buffer);

	return comp_opts;

}





void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)

{

	struct squashfs_sb_info *msblk = sb->s_fs_info;

	void *stream, *comp_opts = get_comp_opts(sb, flags);



	if (IS_ERR(comp_opts))

		return comp_opts;



	stream = squashfs_decompressor_create(msblk, comp_opts);

	if (IS_ERR(stream))

		kfree(comp_opts);



	return strm;

	return stream;

}

fs/squashfs/decompressor.h

+7 −14
Original line number Diff line number Diff line
@@ -24,28 +24,21 @@ 
 */



struct squashfs_decompressor {

	void	*(*init)(struct squashfs_sb_info *, void *, int);

	void	*(*init)(struct squashfs_sb_info *, void *);

	void	*(*comp_opts)(struct squashfs_sb_info *, void *, int);

	void	(*free)(void *);

	int	(*decompress)(struct squashfs_sb_info *, void **,

	int	(*decompress)(struct squashfs_sb_info *, void *, void **,

		struct buffer_head **, int, int, int, int, int);

	int	id;

	char	*name;

	int	supported;

};



static inline void squashfs_decompressor_free(struct squashfs_sb_info *msblk,

	void *s)

static inline void *squashfs_comp_opts(struct squashfs_sb_info *msblk,

							void *buff, int length)

{

	if (msblk->decompressor)

		msblk->decompressor->free(s);

}



static inline int squashfs_decompress(struct squashfs_sb_info *msblk,

	void **buffer, struct buffer_head **bh, int b, int offset, int length,

	int srclength, int pages)

{

	return msblk->decompressor->decompress(msblk, buffer, bh, b, offset,

		length, srclength, pages);

	return msblk->decompressor->comp_opts ?

		msblk->decompressor->comp_opts(msblk, buff, length) : NULL;

}



#ifdef CONFIG_SQUASHFS_XZ

fs/squashfs/decompressor_single.c

0 → 100644
+86 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2013

 * Phillip Lougher <phillip@squashfs.org.uk>

 *

 * This work is licensed under the terms of the GNU GPL, version 2. See

 * the COPYING file in the top-level directory.

 */



#include <linux/types.h>

#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/buffer_head.h>



#include "squashfs_fs.h"

#include "squashfs_fs_sb.h"

#include "decompressor.h"

#include "squashfs.h"



/*

 * This file implements single-threaded decompression in the

 * decompressor framework

 */



struct squashfs_stream {

	void		*stream;

	struct mutex	mutex;

};



void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,

						void *comp_opts)

{

	struct squashfs_stream *stream;

	int err = -ENOMEM;



	stream = kmalloc(sizeof(*stream), GFP_KERNEL);

	if (stream == NULL)

		goto out;



	stream->stream = msblk->decompressor->init(msblk, comp_opts);

	if (IS_ERR(stream->stream)) {

		err = PTR_ERR(stream->stream);

		goto out;

	}



	kfree(comp_opts);

	mutex_init(&stream->mutex);

	return stream;



out:

	kfree(stream);

	return ERR_PTR(err);

}



void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)

{

	struct squashfs_stream *stream = msblk->stream;



	if (stream) {

		msblk->decompressor->free(stream->stream);

		kfree(stream);

	}

}



int squashfs_decompress(struct squashfs_sb_info *msblk,

	void **buffer, struct buffer_head **bh, int b, int offset, int length,

	int srclength, int pages)

{

	int res;

	struct squashfs_stream *stream = msblk->stream;



	mutex_lock(&stream->mutex);

	res = msblk->decompressor->decompress(msblk, stream->stream, buffer,

		bh, b, offset, length, srclength, pages);

	mutex_unlock(&stream->mutex);



	if (res < 0)

		ERROR("%s decompression failed, data probably corrupt\n",

			msblk->decompressor->name);



	return res;

}



int squashfs_max_decompressors(void)

{

	return 1;

}

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