From 5e1dbd5bc3c609c73037a41546c5ead240821558 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 20 Oct 2009 22:12:11 +0200 Subject: mkfs_ext2: another update by Vladimir Signed-off-by: Denys Vlasenko --- util-linux/mkfs_ext2.c | 147 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 95 insertions(+), 52 deletions(-) (limited to 'util-linux/mkfs_ext2.c') diff --git a/util-linux/mkfs_ext2.c b/util-linux/mkfs_ext2.c index 3f4f5c6..be9e363 100644 --- a/util-linux/mkfs_ext2.c +++ b/util-linux/mkfs_ext2.c @@ -75,8 +75,8 @@ static unsigned int_log2(unsigned arg) } // taken from mkfs_minix.c. libbb candidate? -// why "uint64_t size"? we never use it for anything >32 bits -static uint32_t div_roundup(uint64_t size, uint32_t n) +// "uint32_t size", since we never use it for anything >32 bits +static uint32_t div_roundup(uint32_t size, uint32_t n) { // Overflow-resistant uint32_t res = size / n; @@ -176,12 +176,15 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) unsigned blocksize, blocksize_log2; unsigned reserved_percent = 5; unsigned long long kilobytes; - uint32_t nblocks, nblocks_full, nreserved; + uint32_t nblocks, nblocks_full; + uint32_t nreserved; uint32_t ngroups; uint32_t bytes_per_inode; uint32_t first_block; uint32_t inodes_per_group; - uint32_t gdtsz, itsz; + uint32_t group_desc_blocks; + uint32_t inode_table_blocks; + uint32_t lost_and_found_blocks; time_t timestamp; unsigned opts; const char *label = ""; @@ -245,6 +248,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) ) { bb_error_msg_and_die("blocksize %u is bad", blocksize); } + 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 #define blocks_per_group (8 * blocksize) first_block = (EXT2_MIN_BLOCK_SIZE == blocksize); @@ -266,7 +271,6 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) // 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 @@ -279,10 +283,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) retry: // N.B. a block group can have no more than blocks_per_group blocks ngroups = div_roundup(nblocks - first_block, blocks_per_group); - if (0 == ngroups) - bb_error_msg_and_die("ngroups"); - gdtsz = div_roundup(ngroups, blocksize / sizeof(*gd)); + group_desc_blocks = div_roundup(ngroups, blocksize / sizeof(*gd)); // TODO: reserved blocks must be marked as such in the bitmaps, // or resulting filesystem is corrupt if (ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT) { @@ -294,15 +296,15 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) * We set it at 1024x the current filesystem size, or * the upper block count limit (2^32), whichever is lower. */ - uint32_t rgdtsz = 0xFFFFFFFF; // maximum block number - if (nblocks < rgdtsz / 1024) - rgdtsz = nblocks * 1024; - rgdtsz = div_roundup(rgdtsz - first_block, blocks_per_group); - rgdtsz = div_roundup(rgdtsz, blocksize / sizeof(*gd)) - gdtsz; - if (rgdtsz > blocksize / sizeof(uint32_t)) - rgdtsz = blocksize / sizeof(uint32_t); - //TODO: STORE_LE(sb->s_reserved_gdt_blocks, rgdtsz); - gdtsz += rgdtsz; + uint32_t reserved_group_desc_blocks = 0xFFFFFFFF; // maximum block number + if (nblocks < reserved_group_desc_blocks / 1024) + reserved_group_desc_blocks = nblocks * 1024; + reserved_group_desc_blocks = div_roundup(reserved_group_desc_blocks - first_block, blocks_per_group); + reserved_group_desc_blocks = div_roundup(reserved_group_desc_blocks, blocksize / sizeof(*gd)) - group_desc_blocks; + if (reserved_group_desc_blocks > blocksize / sizeof(uint32_t)) + reserved_group_desc_blocks = blocksize / sizeof(uint32_t); + //TODO: STORE_LE(sb->s_reserved_gdt_blocks, reserved_group_desc_blocks); + group_desc_blocks += reserved_group_desc_blocks; } { @@ -324,13 +326,25 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) 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); + inode_table_blocks = div_roundup(inodes_per_group * sizeof(*inode), 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 + /* Or e2fsprogs comment verbatim (what does it mean?): + * Ensure that lost+found is at least 2 blocks, so we always + * test large empty blocks for big-block filesystems. */ + lost_and_found_blocks = MIN(EXT2_NDIR_BLOCKS, 16 >> (blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE)); // 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; + overhead = (has_super(ngroups - 1) ? (1/*sb*/ + group_desc_blocks) : 0) + 1/*bbmp*/ + 1/*ibmp*/ + inode_table_blocks; remainder = (nblocks - first_block) % blocks_per_group; - if ((1 == ngroups) && remainder && (remainder < overhead)) - bb_error_msg_and_die("way small device"); + ////can't happen, nblocks >= 60 guarantees this + ////if ((1 == ngroups) + //// && remainder + //// && (remainder < overhead + 1/* "/" */ + lost_and_found_blocks) + ////) { + //// bb_error_msg_and_die("way small device"); + ////} // Standard mke2fs uses 50. Looks like a bug in our calculation // of "remainder" or "overhead" - we don't match standard mke2fs // when we transition from one group to two groups @@ -363,7 +377,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) , inodes_per_group * ngroups, nblocks , nreserved, reserved_percent , first_block - , gdtsz * (blocksize / sizeof(*gd)) * blocks_per_group + , group_desc_blocks * (blocksize / sizeof(*gd)) * blocks_per_group , ngroups , blocks_per_group, blocks_per_group , inodes_per_group @@ -382,9 +396,11 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) } bb_putchar('\n'); - // dry run? -> we are done - if (opts & OPT_n) - goto done; + if (opts & OPT_n) { + if (ENABLE_FEATURE_CLEAN_UP) + close(fd); + return EXIT_SUCCESS; + } // TODO: 3/5 refuse if mounted // TODO: 4/5 compat options @@ -395,7 +411,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) // TODO: 3/5 dir_index? // fill the superblock - sb = xzalloc(blocksize); + sb = xzalloc(1024); STORE_LE(sb->s_rev_level, 1); // revision 1 filesystem STORE_LE(sb->s_magic, EXT2_SUPER_MAGIC); STORE_LE(sb->s_inode_size, sizeof(*inode)); @@ -444,49 +460,61 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) * don't check all the filesystems at the same time. We use a * kludgy hack of using the UUID to derive a random jitter value. */ - STORE_LE(sb->s_max_mnt_count, EXT2_DFL_MAX_MNT_COUNT + 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 safe_strncpy((char *)sb->s_volume_name, label, sizeof(sb->s_volume_name)); - // fill group descriptors - gd = xzalloc(gdtsz * blocksize); + // calculate filesystem skeleton structures + gd = xzalloc(group_desc_blocks * blocksize); buf = xmalloc(blocksize); sb->s_free_blocks_count = 0; for (i = 0, pos = first_block, n = nblocks - first_block; i < ngroups; i++, pos += blocks_per_group, n -= blocks_per_group ) { - uint32_t overhead = pos + (has_super(i) ? (1/*sb*/ + gdtsz) : 0); - uint32_t fb; + uint32_t overhead = pos + (has_super(i) ? (1/*sb*/ + group_desc_blocks) : 0); + uint32_t free_blocks; + // fill group descriptors STORE_LE(gd[i].bg_block_bitmap, overhead + 0); STORE_LE(gd[i].bg_inode_bitmap, overhead + 1); STORE_LE(gd[i].bg_inode_table, overhead + 2); - overhead = overhead - pos + 1/*bbmp*/ + 1/*ibmp*/ + itsz; + overhead = overhead - pos + 1/*bbmp*/ + 1/*ibmp*/ + inode_table_blocks; gd[i].bg_free_inodes_count = inodes_per_group; //STORE_LE(gd[i].bg_used_dirs_count, 0); - // N.B. both root and lost+found dirs are within the first block group, thus +2 + // N.B. both "/" and "/lost+found" are within the first block group + // "/" occupies 1 block, "/lost+found" occupies lost_and_found_blocks... if (0 == i) { - overhead += 2; + // ... thus increased overhead for the first block group ... + overhead += 1 + lost_and_found_blocks; + // ... and 2 used directories STORE_LE(gd[i].bg_used_dirs_count, 2); + // well known reserved inodes belong to the first block too gd[i].bg_free_inodes_count -= EXT2_GOOD_OLD_FIRST_INO; } + // cache free block count of the group + free_blocks = (n < blocks_per_group ? n : blocks_per_group) - overhead; + // mark preallocated blocks as allocated - fb = (n < blocks_per_group ? n : blocks_per_group) - overhead; -//bb_info_msg("ALLOC: [%u][%u][%u]", blocksize, overhead, blocks_per_group - (fb + overhead)); +//bb_info_msg("ALLOC: [%u][%u][%u]", blocksize, overhead, blocks_per_group - (free_blocks + overhead)); allocate(buf, blocksize, + // reserve "overhead" blocks overhead, - blocks_per_group - (fb + overhead) + // mark unused trailing blocks + blocks_per_group - (free_blocks + overhead) ); // dump block bitmap PUT((uint64_t)(FETCH_LE32(gd[i].bg_block_bitmap)) * blocksize, buf, blocksize); - STORE_LE(gd[i].bg_free_blocks_count, fb); + STORE_LE(gd[i].bg_free_blocks_count, free_blocks); // mark preallocated inodes as allocated allocate(buf, blocksize, + // mark reserved inodes inodes_per_group - gd[i].bg_free_inodes_count, + // mark unused trailing inodes blocks_per_group - inodes_per_group ); // dump inode bitmap @@ -496,7 +524,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) STORE_LE(gd[i].bg_free_inodes_count, gd[i].bg_free_inodes_count); // count overall free blocks - sb->s_free_blocks_count += fb; + sb->s_free_blocks_count += free_blocks; } STORE_LE(sb->s_free_blocks_count, sb->s_free_blocks_count); @@ -506,8 +534,10 @@ 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) + ((0 == i && 0 == first_block) ? 1024 : 0), sb, 1024);//blocksize); - PUT(((uint64_t)pos * blocksize) + blocksize, gd, gdtsz * blocksize); + PUT(((uint64_t)pos * blocksize) + ((0 == i && 1024 != blocksize) ? 1024 : 0), + sb, 1024); + PUT(((uint64_t)pos * blocksize) + blocksize, + gd, group_desc_blocks * blocksize); } } @@ -516,8 +546,9 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) PUT(0, buf, 1024); // N.B. 1024 <= blocksize, so buf[0..1023] contains zeros // zero inode tables for (i = 0; i < ngroups; ++i) - for (n = 0; n < itsz; ++n) - PUT((uint64_t)(FETCH_LE32(gd[i].bg_inode_table) + n) * blocksize, buf, blocksize); + for (n = 0; n < inode_table_blocks; ++n) + PUT((uint64_t)(FETCH_LE32(gd[i].bg_inode_table) + n) * blocksize, + buf, blocksize); // prepare directory inode inode = (struct ext2_inode *)buf; @@ -526,21 +557,34 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) STORE_LE(inode->i_atime, timestamp); STORE_LE(inode->i_ctime, timestamp); STORE_LE(inode->i_size, blocksize); - // N.B. inode->i_blocks stores the number of 512 byte data blocks. Why on Earth?! + // inode->i_blocks stores the number of 512 byte data blocks + // (512, because it goes directly to struct stat without scaling) STORE_LE(inode->i_blocks, blocksize / 512); // 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) + (EXT2_ROOT_INO-1) * sizeof(*inode), buf, sizeof(*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)); // 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) + (EXT2_GOOD_OLD_FIRST_INO-1) * sizeof(*inode), buf, sizeof(*inode)); + STORE_LE(inode->i_size, lost_and_found_blocks * blocksize); + STORE_LE(inode->i_blocks, (lost_and_found_blocks * blocksize) / 512); + n = FETCH_LE32(inode->i_block[0]) + 1; + 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)); + + // zero the blocks for "/lost+found" + memset(buf, 0, blocksize); + for (i = 1; i < lost_and_found_blocks; ++i) + PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + inode_table_blocks + 1+i) * blocksize, + buf, blocksize); // dump directories - memset(buf, 0, blocksize); dir = (struct ext2_dir *)buf; // dump lost+found dir block @@ -554,7 +598,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) STORE_LE(dir->name_len2, 2); STORE_LE(dir->file_type2, EXT2_FT_DIR); dir->name2[0] = '.'; dir->name2[1] = '.'; - PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + itsz + 1) * blocksize, buf, blocksize); + PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + inode_table_blocks + 1) * blocksize, buf, blocksize); // dump root dir block STORE_LE(dir->inode1, EXT2_ROOT_INO); @@ -564,9 +608,8 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) STORE_LE(dir->name_len3, 10); STORE_LE(dir->file_type3, EXT2_FT_DIR); strcpy(dir->name3, "lost+found"); - PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + itsz + 0) * blocksize, buf, blocksize); + PUT((uint64_t)(FETCH_LE32(gd[0].bg_inode_table) + inode_table_blocks + 0) * blocksize, buf, blocksize); - done: // cleanup if (ENABLE_FEATURE_CLEAN_UP) { free(buf); -- cgit v1.1