mkfs_ext2: further work by Vladimir

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
author: Denys Vlasenko <vda.linux@googlemail.com> 2009-10-20 13:34:16 +0200
committer: Denys Vlasenko <vda.linux@googlemail.com> 2009-10-20 13:34:16 +0200
commit: 95484c870645ebda34c9202799f3b31111b90e4f (patch)
tree: 0de582e09d00aa666be04c391ec8abba41afb03d /util-linux/mkfs_ext2.c
parent: 69f2e2cdeba8237d51fe63aa32efbd178ce02663 (diff)
download: busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.tar.gz
busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.tar.bz2
busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.zip
1 files changed, 39 insertions, 39 deletions
diff --git a/util-linux/mkfs_ext2.c b/util-linux/mkfs_ext2.c
index e840f7810..da27dc77d 100644
--- a/util-linux/mkfs_ext2.c
+++ b/util-linux/mkfs_ext2.c
@@ -173,9 +173,9 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
        unsigned i, pos, n;
        unsigned bs, bpi;
        unsigned blocksize, blocksize_log2;
-        unsigned nreserved = 5;
+        unsigned reserved_percent = 5;
        unsigned long long kilobytes;
-        uint32_t nblocks, nblocks_full;
+        uint32_t nblocks, nblocks_full, nreserved;
        uint32_t ngroups;
        uint32_t bytes_per_inode;
        uint32_t first_data_block;
@@ -194,13 +194,9 @@ 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,
-                &nreserved, NULL, NULL, &label, NULL, NULL, NULL, NULL, NULL, NULL);
+                &reserved_percent, NULL, NULL, &label, NULL, NULL, NULL, NULL, NULL, NULL);
        argv += optind; // argv[0] -- device
-        // reserved blocks percentage
-        if (nreserved > 50)
-                bb_error_msg_and_die("-%c is bad", 'm');
        // check the device is a block device
        xmove_fd(xopen(argv[0], O_WRONLY), fd);
        fstat(fd, &st);
@@ -228,14 +224,15 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
        if (opts & OPT_i)
                bytes_per_inode = bpi;
+        // Determine block size
        // block size is a multiple of 1024
        blocksize = 1024;
        if (kilobytes >= 512*1024) // mke2fs 1.41.9 compat
                blocksize = 4096;
        if (EXT2_MAX_BLOCK_SIZE > 4096) {
                // kilobytes >> 22 == size in 4gigabyte chunks.
-                // if it is >= 16k gigs, blocksize must be increased.
+                // if size >= 16k gigs, blocksize must be increased.
-                // Try "mke2fs -F image_std $((16 * 1024*1024*1024))"
+                // Try "mke2fs -F image $((16 * 1024*1024*1024))"
                while ((kilobytes >> 22) >= blocksize)
                        blocksize *= 2;
        }
@@ -247,28 +244,38 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
        ) {
                bb_error_msg_and_die("blocksize %u is bad", blocksize);
        }
+        // number of bits in one block, i.e. 8*blocksize
+#define blocks_per_group (8 * blocksize)
+        first_data_block = (EXT2_MIN_BLOCK_SIZE == blocksize);
        blocksize_log2 = int_log2(blocksize);
+        // Determine number of blocks
        kilobytes >>= (blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE);
-        // nblocks: the total number of blocks in the filesystem
        nblocks = kilobytes;
        if (nblocks != kilobytes)
                bb_error_msg_and_die("block count doesn't fit in 32 bits");
 #define kilobytes kilobytes_unused_after_this
        if (blocksize < PAGE_SIZE)
-                nblocks &= ~((PAGE_SIZE / blocksize)-1);
+                nblocks &= ~((PAGE_SIZE >> blocksize_log2)-1);
+        // Experimentally, standard mke2fs won't work on images smaller than 60k
+        if (nblocks < 60)
+                bb_error_msg_and_die("need >= 60 blocks");
+        // How many reserved blocks?
+        if (reserved_percent > 50)
+                bb_error_msg_and_die("-%c is bad", 'm');
+        //nreserved = div_roundup((uint64_t) nblocks * reserved_percent, 100);
+        nreserved = (uint64_t)nblocks * reserved_percent / 100;
        // N.B. killing e2fsprogs feature! Unused blocks don't account in calculations
        nblocks_full = nblocks;
- retry:
-        if (nblocks < 8)
-                bb_error_msg_and_die("need >= 8 blocks");
-        // number of bits in one block, i.e. 8*blocksize
-#define blocks_per_group (8 * blocksize)
+        // If last block group is too small, nblocks may be decreased in order
+        // to discard it, and control returns here to recalculate some
+        // parameters.
+        // Note: blocksize and bytes_per_inode are never recalculated.
+ retry:
        // N.B. a block group can have no more than blocks_per_group blocks
-        first_data_block = (EXT2_MIN_BLOCK_SIZE == blocksize);
        ngroups = div_roundup(nblocks - first_data_block, blocks_per_group);
        if (0 == ngroups)
                bb_error_msg_and_die("ngroups");
@@ -308,21 +315,21 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                if (inodes_per_group < 16)
                        inodes_per_group = 16;
-                // N.B. a block group can have no more than 8*blocksize inodes
+                // a block group can have no more than 8*blocksize inodes
                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
-                inodes_per_group = (div_roundup(inodes_per_group * sizeof(*inode), blocksize) << blocksize_log2) / sizeof(*inode);
+                inodes_per_group = (div_roundup(inodes_per_group * sizeof(*inode), blocksize) * blocksize) / sizeof(*inode);
                // make sure the number of inodes per group is a multiple of 8
                inodes_per_group &= ~7;
                itsz = div_roundup(inodes_per_group * sizeof(*inode), blocksize);
-                // the last block needs more attention: doesn't it too small for possible overhead?
+                // the last group needs more attention: isn't it too small for possible overhead?
                overhead = (has_super(ngroups - 1) ? (1/*sb*/ + gdtsz) : 0) + 1/*bbmp*/ + 1/*ibmp*/ + itsz;
                remainder = (nblocks - first_data_block) % blocks_per_group;
                if ((1 == ngroups) && remainder && (remainder < overhead))
                        bb_error_msg_and_die("way small device");
-                if (remainder && (remainder < overhead + 50)) {
+                if (remainder && (remainder < overhead + 50/* e2fsprogs hardcoded */)) {
 //bb_info_msg("CHOP[%u]", remainder);
                        nblocks -= remainder;
                        goto retry;
@@ -348,8 +355,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                , blocksize, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE
                , blocksize, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE
                , inodes_per_group * ngroups, nblocks
-                //, div_roundup((uint64_t) nblocks * nreserved, 100), nreserved
+                , nreserved, reserved_percent
-                , (unsigned)((uint64_t) nblocks_full * nreserved / 100), nreserved
                , first_data_block
                , gdtsz * (blocksize / sizeof(*gd)) * blocks_per_group
                , ngroups
@@ -399,7 +405,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
        // blocks
        STORE_LE(sb->s_blocks_count, nblocks);
        // reserve blocks for superuser
-        STORE_LE(sb->s_r_blocks_count, (uint32_t)((uint64_t) nblocks_full * nreserved / 100));
+        STORE_LE(sb->s_r_blocks_count, nreserved);
        // ninodes
        STORE_LE(sb->s_inodes_per_group, inodes_per_group);
        STORE_LE(sb->s_inodes_count, inodes_per_group * ngroups);
@@ -418,7 +424,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                | (EXT2_FEATURE_COMPAT_RESIZE_INO * ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT)
                | (EXT2_FEATURE_COMPAT_DIR_INDEX * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX)
        );
-        // e2fsprogs-1.41.9 doesn't like EXT2_FEATURE_INCOMPAT_WHITEOUT
+        // e2fsck from 1.41.9 doesn't like EXT2_FEATURE_INCOMPAT_WHITEOUT
        STORE_LE(sb->s_feature_incompat, EXT2_FEATURE_INCOMPAT_FILETYPE);// | EXT2_FEATURE_INCOMPAT_WHITEOUT;
        STORE_LE(sb->s_feature_ro_compat, EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER);
        STORE_LE(sb->s_flags, EXT2_FLAGS_SIGNED_HASH * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX);
@@ -435,9 +441,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
        STORE_LE(sb->s_max_mnt_count, EXT2_DFL_MAX_MNT_COUNT
                + (sb->s_uuid[ARRAY_SIZE(sb->s_uuid)-1] % EXT2_DFL_MAX_MNT_COUNT));
-        // write the label, if any
+        // write the label
-        if (label) //opts & OPT_L)
+        safe_strncpy((char *)sb->s_volume_name, label, sizeof(sb->s_volume_name));
-                safe_strncpy((char *)sb->s_volume_name, label, sizeof(sb->s_volume_name));
        // fill group descriptors
        gd = xzalloc(gdtsz * blocksize);
@@ -461,11 +466,6 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                        STORE_LE(gd[i].bg_used_dirs_count, 2);
                        gd[i].bg_free_inodes_count -= EXT2_GOOD_OLD_FIRST_INO;
                }
-//              // N.B. the following is pure heuristics!
-//              // Likely to cope with 1024-byte blocks, when first block is for boot sectors
-//              if (ngroups-1 == i) {
-//                      n -= first_data_block;
-//              }
                // mark preallocated blocks as allocated
                fb = (n < blocks_per_group ? n : blocks_per_group) - overhead;
@@ -500,8 +500,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
                // dump superblock and group descriptors and their backups
                if (has_super(i)) {
                        // N.B. 1024 byte blocks are special
-                        PUT(((uint64_t)pos << blocksize_log2) + ((0 == i && 0 == first_data_block) ? 1024 : 0), sb, 1024);//blocksize);
+                        PUT(((uint64_t)pos * blocksize) + ((0 == i && 0 == first_data_block) ? 1024 : 0), sb, 1024);//blocksize);
-                        PUT(((uint64_t)pos << blocksize_log2) + blocksize, gd, gdtsz * blocksize);
+                        PUT(((uint64_t)pos * blocksize) + blocksize, gd, gdtsz * blocksize);
                }
        }
@@ -526,12 +526,12 @@ 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) + itsz);
-        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) << blocksize_log2) + (EXT2_ROOT_INO-1) * sizeof(*inode), buf, sizeof(*inode));
+        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) * blocksize) + (EXT2_ROOT_INO-1) * sizeof(*inode), buf, sizeof(*inode));
        // dump lost+found dir inode
        STORE_LE(inode->i_links_count, 2); // both "/lost+found" and "/lost+found/." point to this inode
        STORE_LE(inode->i_block[0], inode->i_block[0]+1); // use next block
-        PUT(((uint64_t)FETCH_LE32(gd[0].bg_inode_table) << blocksize_log2) + (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) * sizeof(*inode), buf, sizeof(*inode));
        // dump directories
        memset(buf, 0, blocksize);
author	Denys Vlasenko <vda.linux@googlemail.com>	2009-10-20 13:34:16 +0200
committer	Denys Vlasenko <vda.linux@googlemail.com>	2009-10-20 13:34:16 +0200
commit	95484c870645ebda34c9202799f3b31111b90e4f (patch)
tree	0de582e09d00aa666be04c391ec8abba41afb03d /util-linux/mkfs_ext2.c
parent	69f2e2cdeba8237d51fe63aa32efbd178ce02663 (diff)
download	busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.tar.gz busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.tar.bz2 busybox-w32-95484c870645ebda34c9202799f3b31111b90e4f.zip