2288d86a5
Denys Vlasenko
2009-10-21
Subject
mkfs_ext2: explain why 0.5G+ images are a bit different
Binary
No binary (build failed)
Architecture & Compiler Flags
—
Build Log
(log yok)
Commit Diff GitHub →
util-linux/mkfs_ext2.c+11 -4
| @@ -309,20 +309,23 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) | |
| { | |
| // N.B. e2fsprogs does as follows! | |
| - | // ninodes is the total number of inodes (files) in the file system |
| - | uint32_t ninodes = ((uint64_t) nblocks_full * blocksize) / bytes_per_inode; |
| uint32_t overhead, remainder; | |
| + | // ninodes is the max number of inodes in this filesystem |
| + | uint32_t ninodes = ((uint64_t) nblocks_full * blocksize) / bytes_per_inode; |
| if (ninodes < EXT2_GOOD_OLD_FIRST_INO+1) | |
| ninodes = EXT2_GOOD_OLD_FIRST_INO+1; | |
| inodes_per_group = div_roundup(ninodes, ngroups); | |
| // minimum number because the first EXT2_GOOD_OLD_FIRST_INO-1 are reserved | |
| if (inodes_per_group < 16) | |
| inodes_per_group = 16; | |
| - | |
| - | // a block group can have no more than 8*blocksize inodes |
| + | // a block group can't have more inodes than blocks |
| 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); | |
| // make sure the number of inodes per group is a multiple of 8 | |
| inodes_per_group &= ~7; | |
| @@ -345,6 +348,7 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) | |
| ////) { | |
| //// 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 | |
| @@ -414,6 +418,9 @@ int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) | |
| sb = xzalloc(1024); | |
| STORE_LE(sb->s_rev_level, 1); // 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_first_ino, EXT2_GOOD_OLD_FIRST_INO); | |
| STORE_LE(sb->s_log_block_size, blocksize_log2 - EXT2_MIN_BLOCK_LOG_SIZE); | |