mkfs_ext2: use compatible inode sizes; add -I <inodesize>. (by Vladimir)

function                                             old     new   delta
mkfs_ext2_main                                      2385    2495    +110
packed_usage                                       26400   26447     +47
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 157/0)             Total: 157 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 35 insertions, 20 deletions

diff --git a/util-linux/mkfs_ext2.c b/util-linux/mkfs_ext2.c
index ef22ec7e6..10f7f5fb4 100644
--- a/util-linux/mkfs_ext2.c
+++ b/util-linux/mkfs_ext2.c
@@ -159,7 +159,7 @@ enum {
         OPT_b = 1 << 2,         // block size, in bytes
         OPT_f = 1 << 3,
         OPT_i = 1 << 4,         // bytes per inode
-        OPT_I = 1 << 5,
+        OPT_I = 1 << 5,         // custom inode size, in bytes
         OPT_J = 1 << 6,
         OPT_G = 1 << 7,
         OPT_N = 1 << 8,
@@ -188,6 +188,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
         unsigned i, pos, n;
         unsigned bs, bpi;
         unsigned blocksize, blocksize_log2;
+        unsigned inodesize, user_inodesize;
         unsigned reserved_percent = 5;
         unsigned long long kilobytes;
         uint32_t nblocks, nblocks_full;
@@ -211,7 +212,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
 
         opt_complementary = "-1:b+:m+:i+";
         opts = getopt32(argv, "cl:b:f:i:I:J:G:N:m:o:g:L:M:O:r:E:T:U:jnqvFS",
-                NULL, &bs, NULL, &bpi, NULL, NULL, NULL, NULL,
+                NULL, &bs, NULL, &bpi, &user_inodesize, NULL, NULL, NULL,
                 &reserved_percent, NULL, NULL, &label, NULL, NULL, NULL, NULL, NULL, NULL);
         argv += optind; // argv[0] -- device
 
@@ -249,11 +250,15 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
         if (opts & OPT_i)
                 bytes_per_inode = bpi;
 
-        // Determine block size
+        // Determine block size and inode size
         // block size is a multiple of 1024
+        // inode size is a multiple of 128
         blocksize = 1024;
-        if (kilobytes >= 512*1024) // mke2fs 1.41.9 compat
+        inodesize = sizeof(struct ext2_inode); // 128
+        if (kilobytes >= 512*1024) { // mke2fs 1.41.9 compat
                 blocksize = 4096;
+                inodesize = 256;
+        }
         if (EXT2_MAX_BLOCK_SIZE > 4096) {
                 // kilobytes >> 22 == size in 4gigabyte chunks.
                 // if size >= 16k gigs, blocksize must be increased.
@@ -269,6 +274,18 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
         ) {
                 bb_error_msg_and_die("blocksize %u is bad", blocksize);
         }
+        // Do we have custom inode size?
+        if (opts & OPT_I) {
+                if (user_inodesize < sizeof(*inode)
+                 || user_inodesize > blocksize
+                 || (user_inodesize & (user_inodesize - 1)) // not power of 2
+                ) {
+                        bb_error_msg("-%c is bad", 'I');
+                } else {
+                        inodesize = user_inodesize;
+                }
+        }
+
         if ((int32_t)bytes_per_inode < blocksize)
                 bb_error_msg_and_die("-%c is bad", 'i');
         // number of bits in one block, i.e. 8*blocksize
@@ -340,14 +357,10 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                 if (inodes_per_group > blocks_per_group)
                         inodes_per_group = blocks_per_group;
                 // adjust inodes per group so they completely fill the inode table blocks in the descriptor
-//incompatibility on images >= 0.5GB:
-//difference in sizeof(*inode) sometimes
-//results in slightly bigger inodes_per_group here
-//compared to standard mke2fs:
-                inodes_per_group = (div_roundup(inodes_per_group * sizeof(*inode), blocksize) * blocksize) / sizeof(*inode);
+                inodes_per_group = (div_roundup(inodes_per_group * inodesize, blocksize) * blocksize) / inodesize;
                 // make sure the number of inodes per group is a multiple of 8
                 inodes_per_group &= ~7;
-                inode_table_blocks = div_roundup(inodes_per_group * sizeof(*inode), blocksize);
+                inode_table_blocks = div_roundup(inodes_per_group * inodesize, blocksize);
 
                 // to be useful, lost+found should occupy at least 2 blocks (but not exceeding 16*1024 bytes),
                 // and at most EXT2_NDIR_BLOCKS. So reserve these blocks right now
@@ -434,12 +447,12 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
 
         // fill the superblock
         sb = xzalloc(1024);
-        STORE_LE(sb->s_rev_level, 1); // revision 1 filesystem
+        STORE_LE(sb->s_rev_level, EXT2_DYNAMIC_REV); // revision 1 filesystem
         STORE_LE(sb->s_magic, EXT2_SUPER_MAGIC);
-//incompatibility:
-//on images > 0.5GB, standard mke2fs uses 256 byte inodes.
-//we always use 128 byte ones:
-        STORE_LE(sb->s_inode_size, sizeof(*inode));
+        STORE_LE(sb->s_inode_size, inodesize);
+        // set "Required extra isize" and "Desired extra isize" fields to 28
+        if (inodesize != sizeof(*inode))
+                STORE_LE(sb->s_reserved[21], 0x001C001C);
         STORE_LE(sb->s_first_ino, EXT2_GOOD_OLD_FIRST_INO);
         STORE_LE(sb->s_log_block_size, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
         STORE_LE(sb->s_log_frag_size, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
@@ -592,8 +605,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
         // dump root dir inode
         STORE_LE(inode->i_links_count, 3); // "/.", "/..", "/lost+found/.." point to this inode
         STORE_LE(inode->i_block[0], FETCH_LE32(gd[0].bg_inode_table) + inode_table_blocks);
-        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_ROOT_INO-1) * sizeof(*inode),
-                                buf, sizeof(*inode));
+        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_ROOT_INO-1) * inodesize,
+                                buf, inodesize);
 
         // dump lost+found dir inode
         STORE_LE(inode->i_links_count, 2); // both "/lost+found" and "/lost+found/." point to this inode
@@ -603,8 +616,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
         for (i = 0; i < lost_and_found_blocks; ++i)
                 STORE_LE(inode->i_block[i], i + n); // use next block
 //bb_info_msg("LAST BLOCK USED[%u]", i + n);
-        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_GOOD_OLD_FIRST_INO-1) * sizeof(*inode),
-                                buf, sizeof(*inode));
+        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_GOOD_OLD_FIRST_INO-1) * inodesize,
+                                buf, inodesize);
 
         // dump directories
         memset(buf, 0, blocksize);
diff --git a/util-linux/mkfs_ext2.txt b/util-linux/mkfs_ext2.txt
index 7c551ea04..273d5b644 100644
--- a/util-linux/mkfs_ext2.txt
+++ b/util-linux/mkfs_ext2.txt
@@ -1,5 +1,7 @@
 Difference between bbox mke2fs and standard one (dumpe2fs comparison):
 
+[upd: inode size has been fixed since then]
+
 Two significant differences:
 - standard mke2fs has resize_inode feature and thus has reserved GDT blocks,
   which decreases free blocks;
diff --git a/util-linux/mkfs_ext2_test.sh b/util-linux/mkfs_ext2_test.sh
index 79f8126cd..f5347cc04 100755
--- a/util-linux/mkfs_ext2_test.sh
+++ b/util-linux/mkfs_ext2_test.sh
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 # Disabling features we do not match exactly:
-system_mke2fs='/sbin/mke2fs -I 128 -O ^resize_inode'
+system_mke2fs='/sbin/mke2fs -O ^resize_inode'
 bbox_mke2fs='./busybox mke2fs'
 
 gen_image() { # params: mke2fs_invocation image_name