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-rw-r--r--toys/mke2fs.c108
1 files changed, 93 insertions, 15 deletions
diff --git a/toys/mke2fs.c b/toys/mke2fs.c
index 7d7e5ac7..6b13dd01 100644
--- a/toys/mke2fs.c
+++ b/toys/mke2fs.c
@@ -37,7 +37,7 @@
// On the other hand, we have 128 bits to come up with a unique identifier, of
// which 6 have a defined value. /dev/urandom it is.
-void create_uuid(char *uuid)
+static void create_uuid(char *uuid)
{
// Read 128 random bytes
int fd = xopen("/dev/urandom", O_RDONLY);
@@ -56,20 +56,18 @@ void create_uuid(char *uuid)
// Fill out superblock and TT
-void init_superblock(struct ext2_superblock *sb, off_t length)
+static void init_superblock(struct ext2_superblock *sb)
{
uint32_t temp;
- // Determine appropriate block size, set log_block_size and log_frag_size.
+ // Set log_block_size and log_frag_size.
- if (!TT.blocksize) TT.blocksize = (length && length < 1<<29) ? 1024 : 4096;
- for (temp = 0; temp < 7; temp++) if (TT.blocksize == 1024<<temp) break;
- if (temp==7) error_exit("bad blocksize");
+ for (temp = 0; temp < 4; temp++) if (TT.blocksize == 1024<<temp) break;
+ if (temp==4) error_exit("bad blocksize");
sb->log_block_size = sb->log_frag_size = SWAP_LE32(temp);
// Fill out blocks_count, r_blocks_count, first_data_block
- if (!TT.blocks) TT.blocks = length/TT.blocksize;
sb->blocks_count = SWAP_LE32(TT.blocks);
if (!TT.reserved_percent) TT.reserved_percent = 5;
@@ -130,10 +128,30 @@ void init_superblock(struct ext2_superblock *sb, off_t length)
// sb->feature_compat = SWAP_LE32(EXT3_FEATURE_COMPAT_HAS_JOURNAL);
}
+// Number of blocks used in this group by superblock/group list backup.
+// Returns 0 if this group doesn't have a superblock backup.
+static int group_superblock_used(uint32_t group)
+{
+ int used ;
+
+ if (0) return 0; // todo, which groups have no superblock?
+
+ // How blocks does the group table take up?
+ used = TT.groups * sizeof(struct ext2_group);
+ used += TT.blocksize - 1;
+ used /= TT.blocksize;
+ // Plus the superblock itself.
+ used++;
+ // And a corner case.
+ if (!group && TT.blocksize == 1024) used++;
+
+ return used;
+}
+
int mke2fs_main(void)
{
- struct ext2_superblock *sb = xzalloc(sizeof(struct ext2_superblock));
- int temp;
+ int i, temp;
+ off_t length;
// Handle command line arguments.
@@ -149,17 +167,77 @@ int mke2fs_main(void)
// For mke?fs, open file. For gene?fs, create file.
TT.fsfd = xcreate(*toys.optargs, temp, 0777);
- // We skip the first 1k (to avoid the boot sector, if any). Use this to
+ // Determine appropriate block size and block count from file length.
+
+ length = fdlength(TT.fsfd);
+ if (length<1) error_exit("gene2fs is a todo item");
+ if (!TT.blocksize) TT.blocksize = (length && length < 1<<29) ? 1024 : 4096;
+ if (!TT.blocks) TT.blocks = length/TT.blocksize;
+
+ // Skip the first 1k to avoid the boot sector (if any). Use this to
// figure out if this file is seekable.
if(-1 == lseek(TT.fsfd, 1024, SEEK_SET)) {
TT.noseek=1;
- xwrite(TT.fsfd, sb, 1024);
+ xwrite(TT.fsfd, &TT.sb, 1024);
}
- // Create and write first superblock.
-
- init_superblock(sb, fdlength(TT.fsfd));
- xwrite(TT.fsfd, sb, sizeof(struct ext2_superblock)); // 4096-1024
+ // Initialize superblock structure
+
+ init_superblock(&TT.sb);
+
+ // Loop through block groups.
+
+ for (i=0; i<TT.groups; i++) {
+ // If a superblock goes here, write it out.
+ if (group_superblock_used(i)) {
+ struct ext2_group *bg = (struct ext2_group *)toybuf;
+ int j;
+
+ TT.sb.block_group_nr = SWAP_LE16(i);
+
+ // Write superblock and pad it up to block size
+ xwrite(TT.fsfd, &TT.sb, sizeof(struct ext2_superblock));
+ temp = TT.blocksize - sizeof(struct ext2_superblock);
+ if (!i && TT.blocksize > 1024) temp -= 1024;
+ memset(toybuf, 0, TT.blocksize);
+ xwrite(TT.fsfd, toybuf, temp);
+
+ // Loop through groups to write group descriptor table.
+ for(j=0; j<TT.groups; j++) {
+ uint32_t start, used, k;
+
+ // Figure out what sector this group starts in.
+ start = j*TT.blocksize*8;
+ used = group_superblock_used(j);
+
+ // Find next array slot in this block (flush block if full).
+ k = j % (TT.blocksize/sizeof(struct ext2_group));
+ if (!k) {
+ if (j) write(TT.fsfd, bg, TT.blocksize);
+ memset(bg, 0, TT.blocksize);
+ }
+
+ // sb.inodes_per_group is uint32_t, but group.free_inodes_count
+ // is uint16_t. Add in endianness conversion and this little
+ // dance is called for.
+ temp = SWAP_LE32(TT.sb.inodes_per_group);
+ bg[k].free_inodes_count = SWAP_LE16(temp);
+
+ // How many blocks used by inode table?
+ temp *= sizeof(struct ext2_inode);
+ temp /= TT.blocksize;
+
+ // Fill out rest of group structure
+ bg[k].block_bitmap = SWAP_LE32(start+(used++));
+ bg[k].inode_bitmap = SWAP_LE32(start+(used++));
+ bg[k].inode_table = SWAP_LE32(start+used);
+ temp = (TT.blocksize*8)-used-temp;
+ bg[k].free_blocks_count = SWAP_LE32(temp);
+ bg[k].used_dirs_count = 0;
+ }
+ write(TT.fsfd, bg, TT.blocksize);
+ }
+ }
return 0;
}