Squashfs: Generalise paging handling in the decompressors

Further generalise the decompressors by adding a page handler
abstraction.  This adds helpers to allow the decompressors
to access and process the output buffers in an implementation
independant manner.

This allows different types of output buffer to be passed
to the decompressors, with the implementation specific
aspects handled at decompression time, but without the
knowledge being held in the decompressor wrapper code.

This will allow the decompressors to handle Squashfs
cache buffers, and page cache pages.

This patch adds the abstraction and an implementation for
the caches.

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

1 files changed, 13 insertions, 9 deletions

diff --git a/fs/squashfs/xz_wrapper.c b/fs/squashfs/xz_wrapper.c
index 5d1d07cca6b4..c609624e4b8a 100644
--- a/fs/squashfs/xz_wrapper.c
+++ b/fs/squashfs/xz_wrapper.c
@@ -32,6 +32,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 struct squashfs_xz {
 	struct xz_dec *state;
@@ -129,11 +130,11 @@ static void squashfs_xz_free(void *strm)
 
 
 static int squashfs_xz_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 buffer_head **bh, int b, int offset, int length,
+	struct squashfs_page_actor *output)
 {
 	enum xz_ret xz_err;
-	int avail, total = 0, k = 0, page = 0;
+	int avail, total = 0, k = 0;
 	struct squashfs_xz *stream = strm;
 
 	xz_dec_reset(stream->state);
@@ -141,7 +142,7 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
 	stream->buf.in_size = 0;
 	stream->buf.out_pos = 0;
 	stream->buf.out_size = PAGE_CACHE_SIZE;
-	stream->buf.out = buffer[page++];
+	stream->buf.out = squashfs_first_page(output);
 
 	do {
 		if (stream->buf.in_pos == stream->buf.in_size && k < b) {
@@ -153,11 +154,12 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
 			offset = 0;
 		}
 
-		if (stream->buf.out_pos == stream->buf.out_size
-							&& page < pages) {
-			stream->buf.out = buffer[page++];
-			stream->buf.out_pos = 0;
-			total += PAGE_CACHE_SIZE;
+		if (stream->buf.out_pos == stream->buf.out_size) {
+			stream->buf.out = squashfs_next_page(output);
+			if (stream->buf.out != NULL) {
+				stream->buf.out_pos = 0;
+				total += PAGE_CACHE_SIZE;
+			}
 		}
 
 		xz_err = xz_dec_run(stream->state, &stream->buf);
@@ -166,6 +168,8 @@ static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
 			put_bh(bh[k++]);
 	} while (xz_err == XZ_OK);
 
+	squashfs_finish_page(output);
+
 	if (xz_err != XZ_STREAM_END || k < b)
 		goto out;