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, 11 insertions, 3 deletions

diff --git a/fs/squashfs/decompressor.c b/fs/squashfs/decompressor.c
index 234291f79ba5..ac22fe73b0ad 100644
--- a/fs/squashfs/decompressor.c
+++ b/fs/squashfs/decompressor.c
@@ -30,6 +30,7 @@
 #include "squashfs_fs_sb.h"
 #include "decompressor.h"
 #include "squashfs.h"
+#include "page_actor.h"
 
 /*
  * This file (and decompressor.h) implements a decompressor framework for
@@ -87,6 +88,7 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
 {
 	struct squashfs_sb_info *msblk = sb->s_fs_info;
 	void *buffer = NULL, *comp_opts;
+	struct squashfs_page_actor *actor = NULL;
 	int length = 0;
 
 	/*
@@ -99,9 +101,14 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
 			goto out;
 		}
 
-		length = squashfs_read_data(sb, &buffer,
-			sizeof(struct squashfs_super_block), 0, NULL,
-				PAGE_CACHE_SIZE, 1);
+		actor = squashfs_page_actor_init(&buffer, 1, 0);
+		if (actor == NULL) {
+			comp_opts = ERR_PTR(-ENOMEM);
+			goto out;
+		}
+
+		length = squashfs_read_data(sb,
+			sizeof(struct squashfs_super_block), 0, NULL, actor);
 
 		if (length < 0) {
 			comp_opts = ERR_PTR(length);
@@ -112,6 +119,7 @@ static void *get_comp_opts(struct super_block *sb, unsigned short flags)
 	comp_opts = squashfs_comp_opts(msblk, buffer, length);
 
 out:
+	kfree(actor);
 	kfree(buffer);
 	return comp_opts;
 }