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 <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>

1 files changed, 7 insertions, 14 deletions

diff --git a/fs/squashfs/decompressor.h b/fs/squashfs/decompressor.h
index 330073e29029..6cdb20a3878a 100644
--- a/fs/squashfs/decompressor.h
+++ b/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