Revert "Squashfs: optimize reading uncompressed data"

This reverts commit 0c2f831.

Change-Id: Iaf0c9182c682e4c92e78abeb283c96b30c756d21
Reviewed-on: https://tp-biosrd-v02/gerrit/81524
Reviewed-by: Alex Cheng(鄭富元) <Alex_Cheng@asus.com>
Tested-by: Alex Cheng(鄭富元) <Alex_Cheng@asus.com>

Author: alex3788

fs/squashfs/block.c

@@ -206,22 +206,6 @@ static void squashfs_bio_end_io(struct bio *bio)
 	kfree(bio_req);
 }
 
-static int bh_is_optional(struct squashfs_read_request *req, int idx)
-{
-	int start_idx, end_idx;
-	struct squashfs_sb_info *msblk = req->sb->s_fs_info;
-
-	start_idx = (idx * msblk->devblksize - req->offset) / PAGE_CACHE_SIZE;
-	end_idx = ((idx + 1) * msblk->devblksize - req->offset + 1) / PAGE_CACHE_SIZE;
-	if (start_idx >= req->output->pages)
-		return 1;
-	if (start_idx < 0)
-		start_idx = end_idx;
-	if (end_idx >= req->output->pages)
-		end_idx = start_idx;
-	return !req->output->page[start_idx] && !req->output->page[end_idx];
-}
-
 static int actor_getblks(struct squashfs_read_request *req, u64 block)
 {
 	int i;
@@ -231,15 +215,6 @@ static int actor_getblks(struct squashfs_read_request *req, u64 block)
 		return -ENOMEM;
 
 	for (i = 0; i < req->nr_buffers; ++i) {
-		/*
-		 * When dealing with an uncompressed block, the actor may
-		 * contains NULL pages. There's no need to read the buffers
-		 * associated with these pages.
-		 */
-		if (!req->compressed && bh_is_optional(req, i)) {
-			req->bh[i] = NULL;
-			continue;
-		}
 		req->bh[i] = sb_getblk(req->sb, block + i);
 		if (!req->bh[i]) {
 			while (--i) {

fs/squashfs/file_direct.c

@@ -114,38 +114,15 @@ int squashfs_readpages_block(struct page *target_page,
 	struct squashfs_page_actor *actor;
 	struct inode *inode = mapping->host;
 	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
-	int start_index, end_index, file_end, actor_pages, res;
+	int file_end = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
 	int mask = (1 << (msblk->block_log - PAGE_CACHE_SHIFT)) - 1;
+	int start_index = page_index & ~mask;
+	int end_index = start_index | mask;
+	int actor_pages, res;
 
-	/*
-	 * If readpage() is called on an uncompressed datablock, we can just
-	 * read the pages instead of fetching the whole block.
-	 * This greatly improves the performance when a process keep doing
-	 * random reads because we only fetch the necessary data.
-	 * The readahead algorithm will take care of doing speculative reads
-	 * if necessary.
-	 * We can't read more than 1 block even if readahead provides use more
-	 * pages because we don't know yet if the next block is compressed or
-	 * not.
-	 */
-	if (bsize && !SQUASHFS_COMPRESSED_BLOCK(bsize)) {
-		u64 block_end = block + msblk->block_size;
-
-		block += (page_index & mask) * PAGE_CACHE_SIZE;
-		actor_pages = (block_end - block) / PAGE_CACHE_SIZE;
-		if (*nr_pages < actor_pages)
-			actor_pages = *nr_pages;
-		start_index = page_index;
-		bsize = min_t(int, bsize, (PAGE_CACHE_SIZE * actor_pages)
-					  | SQUASHFS_COMPRESSED_BIT_BLOCK);
-	} else {
-		file_end = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
-		start_index = page_index & ~mask;
-		end_index = start_index | mask;
-		if (end_index > file_end)
-			end_index = file_end;
-		actor_pages = end_index - start_index + 1;
-	}
+	if (end_index > file_end)
+		end_index = file_end;
+	actor_pages = end_index - start_index + 1;
 
 	actor = actor_from_page_cache(actor_pages, target_page,
 				      readahead_pages, nr_pages, start_index,