Add support for EXT2_FEATURE_COMPAT_LAZY_BG

This feature is initially intended for testing purposes; it allows an
ext2/ext3 developer to create very large filesystems using sparse files
where most of the block groups are not initialized and so do not require
much disk space.  Eventually it could be used as a way of speeding up
mke2fs and e2fsck for large filesystem, but that would be best done by 
adding an RO_COMPAT extension to the filesystem to allow the inode table
to be lazily initialized on a per-block basis, instead of being entirely initialized
or entirely unused on a per-blockgroup basis.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 63 insertions, 10 deletions

diff --git a/e2fsck/pass5.c b/e2fsck/pass5.c
index e708fa41..eb3ebf02 100644
--- a/e2fsck/pass5.c
+++ b/e2fsck/pass5.c
@@ -111,7 +111,7 @@ static void print_bitmap_problem(e2fsck_t ctx, int problem,
 static void check_block_bitmaps(e2fsck_t ctx)
 {
 	ext2_filsys fs = ctx->fs;
-	blk_t	i;
+	blk_t	i, super;
 	int	*free_array;
 	int	group = 0;
 	unsigned int	blocks = 0;
@@ -121,6 +121,8 @@ static void check_block_bitmaps(e2fsck_t ctx)
 	struct problem_context	pctx;
 	int	problem, save_problem, fixit, had_problem;
 	errcode_t	retval;
+	int		lazy_bg = 0;
+	int		skip_group = 0;
 	
 	clear_problem_context(&pctx);
 	free_array = (int *) e2fsck_allocate_memory(ctx,
@@ -156,19 +158,45 @@ static void check_block_bitmaps(e2fsck_t ctx)
 		return;
 	}
 		       
+	if (EXT2_HAS_COMPAT_FEATURE(fs->super, 
+				    EXT2_FEATURE_COMPAT_LAZY_BG))
+		lazy_bg++;
+
 redo_counts:
 	had_problem = 0;
 	save_problem = 0;
 	pctx.blk = pctx.blk2 = NO_BLK;
+	if (lazy_bg && (fs->group_desc[group].bg_flags &
+			EXT2_BG_BLOCK_UNINIT))
+		skip_group++;
+	super = fs->super->s_first_data_block;
 	for (i = fs->super->s_first_data_block;
 	     i < fs->super->s_blocks_count;
 	     i++) {
 		actual = ext2fs_fast_test_block_bitmap(ctx->block_found_map, i);
-		bitmap = ext2fs_fast_test_block_bitmap(fs->block_map, i);
+
+		if (skip_group) {
+			if ((i >= super) &&
+			    (i <= super + fs->desc_blocks) &&
+			    ext2fs_bg_has_super(fs, group))
+				bitmap = 1;
+			else if (i == fs->group_desc[group].bg_block_bitmap)
+				bitmap = 1;
+			else if (i == fs->group_desc[group].bg_inode_bitmap)
+				bitmap = 1;
+			else if (i >= fs->group_desc[group].bg_inode_table &&
+				 (i < fs->group_desc[group].bg_inode_table
+				  + fs->inode_blocks_per_group))
+				bitmap = 1;
+			else
+				bitmap = 0;
+			actual = (actual != 0);
+		} else
+			bitmap = ext2fs_fast_test_block_bitmap(fs->block_map, i);
 		
 		if (actual == bitmap)
 			goto do_counts;
-		
+
 		if (!actual && bitmap) {
 			/*
 			 * Block not used, but marked in use in the bitmap.
@@ -197,7 +225,7 @@ redo_counts:
 		had_problem++;
 		
 	do_counts:
-		if (!bitmap) {
+		if (!bitmap && !skip_group) {
 			group_free++;
 			free_blocks++;
 		}
@@ -208,10 +236,17 @@ redo_counts:
 			group ++;
 			blocks = 0;
 			group_free = 0;
+			skip_group = 0;
+			super += fs->super->s_blocks_per_group;
 			if (ctx->progress)
 				if ((ctx->progress)(ctx, 5, group,
 						    fs->group_desc_count*2))
 					return;
+			if (lazy_bg &&
+			    (i != fs->super->s_blocks_count-1) &&
+			    (fs->group_desc[group].bg_flags &
+			     EXT2_BG_BLOCK_UNINIT))
+				skip_group++;
 		}
 	}
 	if (pctx.blk != NO_BLK)
@@ -286,6 +321,8 @@ static void check_inode_bitmaps(e2fsck_t ctx)
 	errcode_t	retval;
 	struct problem_context	pctx;
 	int		problem, save_problem, fixit, had_problem;
+	int		lazy_bg = 0;
+	int		skip_group = 0;
 	
 	clear_problem_context(&pctx);
 	free_array = (int *) e2fsck_allocate_memory(ctx,
@@ -321,14 +358,24 @@ static void check_inode_bitmaps(e2fsck_t ctx)
 		return;
 	}
 
+	if (EXT2_HAS_COMPAT_FEATURE(fs->super, 
+				    EXT2_FEATURE_COMPAT_LAZY_BG))
+		lazy_bg++;
+
 redo_counts:
 	had_problem = 0;
 	save_problem = 0;
 	pctx.ino = pctx.ino2 = 0;
+	if (lazy_bg && (fs->group_desc[group].bg_flags &
+			EXT2_BG_INODE_UNINIT))
+		skip_group++;
+
 	for (i = 1; i <= fs->super->s_inodes_count; i++) {
 		actual = ext2fs_fast_test_inode_bitmap(ctx->inode_used_map, i);
-		bitmap = ext2fs_fast_test_inode_bitmap(fs->inode_map, i);
-		
+		if (skip_group) 
+			bitmap = 0;
+		else
+			bitmap = ext2fs_fast_test_inode_bitmap(fs->inode_map, i);
 		if (actual == bitmap)
 			goto do_counts;
 		
@@ -360,12 +407,12 @@ redo_counts:
 		had_problem++;
 		
 do_counts:
-		if (!bitmap) {
-			group_free++;
-			free_inodes++;
-		} else {
+		if (bitmap) {
 			if (ext2fs_test_inode_bitmap(ctx->inode_dir_map, i))
 				dirs_count++;
+		} else if (!skip_group) {
+			group_free++;
+			free_inodes++;
 		}
 		inodes++;
 		if ((inodes == fs->super->s_inodes_per_group) ||
@@ -374,6 +421,7 @@ do_counts:
 			dir_array[group] = dirs_count;
 			group ++;
 			inodes = 0;
+			skip_group = 0;
 			group_free = 0;
 			dirs_count = 0;
 			if (ctx->progress)
@@ -381,6 +429,11 @@ do_counts:
 					    group + fs->group_desc_count,
 					    fs->group_desc_count*2))
 					return;
+			if (lazy_bg &&
+			    (i != fs->super->s_inodes_count) &&
+			    (fs->group_desc[group].bg_flags &
+			     EXT2_BG_INODE_UNINIT))
+				skip_group++;
 		}
 	}
 	if (pctx.ino)