[rfc, patch 3/3] larger block group descriptors

add to mke2fs a new '-D' option that specifies the descriptor size.
This patch is for testing purposes only; indeed we need to create a
file system in order to test the above patches :-)


Index: e2fsprogs-1.39/misc/mke2fs.c
===================================================================
--- e2fsprogs-1.39.orig/misc/mke2fs.c	2006-06-07 13:41:04.000000000 +0200
+++ e2fsprogs-1.39/misc/mke2fs.c	2006-06-07 13:43:24.000000000 +0200
@@ -676,6 +676,7 @@ static void show_stats(ext2_filsys fs)
 		s->s_log_block_size);
 	printf(_("Fragment size=%u (log=%u)\n"), fs->fragsize,
 		s->s_log_frag_size);
+	printf(_("Descriptor size=%u\n"), fs->desc_size);
 	printf(_("%u inodes, %u blocks\n"), s->s_inodes_count,
 	       s->s_blocks_count);
 	printf(_("%u blocks (%2.2f%%) reserved for the super user\n"),
@@ -892,6 +893,7 @@ static void PRS(int argc, char *argv[])
 	int		blocksize = 0;
 	int		inode_ratio = 0;
 	int		inode_size = 0;
+	int		desc_size = 0;
 	double		reserved_ratio = 5.0;
 	int		sector_size = 0;
 	int		show_version_only = 0;
@@ -967,7 +969,7 @@ static void PRS(int argc, char *argv[])
 	}
 
 	while ((c = getopt (argc, argv,
-		    "b:cf:g:i:jl:m:no:qr:s:tvE:FI:J:L:M:N:O:R:ST:V")) != EOF) {
+		    "b:cf:g:i:jl:m:no:qr:s:tvD:E:FI:J:L:M:N:O:R:ST:V")) != EOF) {
 		switch (c) {
 		case 'b':
 			blocksize = strtol(optarg, &tmp, 0);
@@ -1089,6 +1091,14 @@ static void PRS(int argc, char *argv[])
 		case 'v':
 			verbose = 1;
 			break;
+		case 'D':
+			desc_size = strtoul(optarg, &tmp, 0);
+			if (*tmp) {
+				com_err(program_name, 0,
+					_("invalid inode size - %s"), optarg);
+				exit(1);
+			}
+			break;
 		case 'F':
 			force = 1;
 			break;
@@ -1430,6 +1440,23 @@ static void PRS(int argc, char *argv[])
 		fs_param.s_inode_size = inode_size;
 	}
 
+	if (desc_size) {
+		if (desc_size < EXT2_MIN_DESC_SIZE ||
+		    desc_size > EXT2_MAX_DESC_SIZE ||
+		    desc_size & (desc_size - 1)) {
+			com_err(program_name, 0,
+				_("invalid descriptor size %d (min %d/max %d)"),
+				desc_size, EXT2_MIN_DESC_SIZE,
+				EXT2_MAX_DESC_SIZE);
+			exit(1);
+		}
+		fs_param.s_desc_size = desc_size;
+		if (desc_size != EXT2_MIN_DESC_SIZE) {
+			fs_param.s_feature_incompat |= 
+			    EXT3_FEATURE_INCOMPAT_DESC_SIZE;
+		}
+	}
+
 	/*
 	 * Calculate number of inodes based on the inode ratio
 	 */