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: Phillip Lougher <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>

fs/squashfs/Makefile

@@ -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

@@ -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

@@ -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[] = {
@@ -83,34 +83,51 @@ 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;
 
 	/*
 	 * Read decompressor specific options from file system if present
 	 */
 	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);
+				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

@@ -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

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2013
+ * Phillip Lougher <[email protected]>
+ *
+ * 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;
+}

fs/squashfs/lzo_wrapper.c

@@ -37,7 +37,7 @@ struct squashfs_lzo {
 	void	*output;
 };
 
-static void *lzo_init(struct squashfs_sb_info *msblk, void *buff, int len)
+static void *lzo_init(struct squashfs_sb_info *msblk, void *buff)
 {
 	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
 
@@ -74,22 +74,16 @@ static void lzo_free(void *strm)
 }
 
 
-static int lzo_uncompress(struct squashfs_sb_info *msblk, void **buffer,
-	struct buffer_head **bh, int b, int offset, int length, int srclength,
-	int pages)
+static int lzo_uncompress(struct squashfs_sb_info *msblk, void *strm,
+	void **buffer, struct buffer_head **bh, int b, int offset, int length,
+	int srclength, int pages)
 {
-	struct squashfs_lzo *stream = msblk->stream;
+	struct squashfs_lzo *stream = strm;
 	void *buff = stream->input;
 	int avail, i, bytes = length, res;
 	size_t out_len = srclength;
 
-	mutex_lock(&msblk->read_data_mutex);
-
 	for (i = 0; i < b; i++) {
-		wait_on_buffer(bh[i]);
-		if (!buffer_uptodate(bh[i]))
-			goto block_release;
-
 		avail = min(bytes, msblk->devblksize - offset);
 		memcpy(buff, bh[i]->b_data + offset, avail);
 		buff += avail;
@@ -111,17 +105,9 @@ static int lzo_uncompress(struct squashfs_sb_info *msblk, void **buffer,
 		bytes -= avail;
 	}
 
-	mutex_unlock(&msblk->read_data_mutex);
 	return res;
 
-block_release:
-	for (; i < b; i++)
-		put_bh(bh[i]);
-
 failed:
-	mutex_unlock(&msblk->read_data_mutex);
-
-	ERROR("lzo decompression failed, data probably corrupt\n");
 	return -EIO;
 }
 

fs/squashfs/squashfs.h

@@ -48,7 +48,14 @@ extern void *squashfs_read_table(struct super_block *, u64, int);
 
 /* decompressor.c */
 extern const struct squashfs_decompressor *squashfs_lookup_decompressor(int);
-extern void *squashfs_decompressor_init(struct super_block *, unsigned short);
+extern void *squashfs_decompressor_setup(struct super_block *, unsigned short);
+
+/* decompressor_xxx.c */
+extern void *squashfs_decompressor_create(struct squashfs_sb_info *, void *);
+extern void squashfs_decompressor_destroy(struct squashfs_sb_info *);
+extern int squashfs_decompress(struct squashfs_sb_info *, void **,
+	struct buffer_head **, int, int, int, int, int);
+extern int squashfs_max_decompressors(void);
 
 /* export.c */
 extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64, u64,

fs/squashfs/squashfs_fs_sb.h

@@ -63,10 +63,9 @@ struct squashfs_sb_info {
 	__le64					*id_table;
 	__le64					*fragment_index;
 	__le64					*xattr_id_table;
-	struct mutex				read_data_mutex;
 	struct mutex				meta_index_mutex;
 	struct meta_index			*meta_index;
-	void					*stream;
+	struct squashfs_stream			*stream;
 	__le64					*inode_lookup_table;
 	u64					inode_table;
 	u64					directory_table;

fs/squashfs/super.c

@@ -98,7 +98,6 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
 	msblk->devblksize_log2 = ffz(~msblk->devblksize);
 
-	mutex_init(&msblk->read_data_mutex);
 	mutex_init(&msblk->meta_index_mutex);
 
 	/*
@@ -206,13 +205,14 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 
 	/* Allocate read_page block */
-	msblk->read_page = squashfs_cache_init("data", 1, msblk->block_size);
+	msblk->read_page = squashfs_cache_init("data",
+		squashfs_max_decompressors(), msblk->block_size);
 	if (msblk->read_page == NULL) {
 		ERROR("Failed to allocate read_page block\n");
 		goto failed_mount;
 	}
 
-	msblk->stream = squashfs_decompressor_init(sb, flags);
+	msblk->stream = squashfs_decompressor_setup(sb, flags);
 	if (IS_ERR(msblk->stream)) {
 		err = PTR_ERR(msblk->stream);
 		msblk->stream = NULL;
@@ -336,7 +336,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	squashfs_cache_delete(msblk->block_cache);
 	squashfs_cache_delete(msblk->fragment_cache);
 	squashfs_cache_delete(msblk->read_page);
-	squashfs_decompressor_free(msblk, msblk->stream);
+	squashfs_decompressor_destroy(msblk);
 	kfree(msblk->inode_lookup_table);
 	kfree(msblk->fragment_index);
 	kfree(msblk->id_table);
@@ -383,7 +383,7 @@ static void squashfs_put_super(struct super_block *sb)
 		squashfs_cache_delete(sbi->block_cache);
 		squashfs_cache_delete(sbi->fragment_cache);
 		squashfs_cache_delete(sbi->read_page);
-		squashfs_decompressor_free(sbi, sbi->stream);
+		squashfs_decompressor_destroy(sbi);
 		kfree(sbi->id_table);
 		kfree(sbi->fragment_index);
 		kfree(sbi->meta_index);