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, 18 insertions, 9 deletions

diff --git a/fs/squashfs/lzo_wrapper.c b/fs/squashfs/lzo_wrapper.c
index 75c3b5779172..244b9fbfff7b 100644
--- a/fs/squashfs/lzo_wrapper.c
+++ b/fs/squashfs/lzo_wrapper.c
@@ -31,6 +31,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs.h"
 #include "decompressor.h"
+#include "page_actor.h"
 
 struct squashfs_lzo {
         void    *input;
@@ -75,13 +76,13 @@ static void lzo_free(void *strm)
 
 
 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 buffer_head **bh, int b, int offset, int length,
+        struct squashfs_page_actor *output)
 {
         struct squashfs_lzo *stream = strm;
-        void *buff = stream->input;
+        void *buff = stream->input, *data;
         int avail, i, bytes = length, res;
-        size_t out_len = srclength;
+        size_t out_len = output->length;
 
         for (i = 0; i < b; i++) {
                 avail = min(bytes, msblk->devblksize - offset);
@@ -98,12 +99,20 @@ static int lzo_uncompress(struct squashfs_sb_info *msblk, void *strm,
                 goto failed;
 
         res = bytes = (int)out_len;
-        for (i = 0, buff = stream->output; bytes && i < pages; i++) {
-                avail = min_t(int, bytes, PAGE_CACHE_SIZE);
-                memcpy(buffer[i], buff, avail);
-                buff += avail;
-                bytes -= avail;
+        data = squashfs_first_page(output);
+        buff = stream->output;
+        while (data) {
+                if (bytes <= PAGE_CACHE_SIZE) {
+                        memcpy(data, buff, bytes);
+                        break;
+                } else {
+                        memcpy(data, buff, PAGE_CACHE_SIZE);
+                        buff += PAGE_CACHE_SIZE;
+                        bytes -= PAGE_CACHE_SIZE;
+                        data = squashfs_next_page(output);
+                }
         }
+        squashfs_finish_page(output);
 
         return res;