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mkfs_ext2: explain 256-byte inodes. no code changes

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-10-21 11:34:32 +02:00
parent 2288d86a54
commit 2ee2724a41
1 changed files with 39 additions and 19 deletions
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58
util-linux/mkfs_ext2.c
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@ -120,16 +120,45 @@ static uint32_t has_super(uint32_t x)
} }
} }
/* Standard mke2fs 1.41.9: #define fd 3 /* predefined output descriptor */
* Usage: mke2fs [-c|-l filename] [-b block-size] [-f fragment-size]
* [-i bytes-per-inode] [-I inode-size] [-J journal-options] static void PUT(uint64_t off, void *buf, uint32_t size)
* [-G meta group size] [-N number-of-inodes] {
* [-m reserved-blocks-percentage] [-o creator-os] // bb_info_msg("PUT[%llu]:[%u]", off, size);
* [-g blocks-per-group] [-L volume-label] [-M last-mounted-directory] xlseek(fd, off, SEEK_SET);
* [-O feature[,...]] [-r fs-revision] [-E extended-option[,...]] xwrite(fd, buf, size);
* [-T fs-type] [-U UUID] [-jnqvFSV] device [blocks-count] }
*/
// N.B. not commented below options are taken and silently ignored // 128 and 256-byte inodes:
// 128-byte inode is described by struct ext2_inode.
// 256-byte one just has these fields appended:
// __u16 i_extra_isize;
// __u16 i_pad1;
// __u32 i_ctime_extra; /* extra Change time (nsec << 2 | epoch) */
// __u32 i_mtime_extra; /* extra Modification time (nsec << 2 | epoch) */
// __u32 i_atime_extra; /* extra Access time (nsec << 2 | epoch) */
// __u32 i_crtime; /* File creation time */
// __u32 i_crtime_extra; /* extra File creation time (nsec << 2 | epoch)*/
// __u32 i_version_hi; /* high 32 bits for 64-bit version */
// the rest is padding.
//
// linux/ext2_fs.h has "#define i_size_high i_dir_acl" which suggests that even
// 128-byte inode is capable of describing large files (i_dir_acl is meaningful
// only for directories, which never need i_size_high).
//
// Standard mke2fs creates a filesystem with 256-byte inodes if it is
// bigger than 0.5GB. So far, we do not do this.
// Standard mke2fs 1.41.9:
// Usage: mke2fs [-c|-l filename] [-b block-size] [-f fragment-size]
// [-i bytes-per-inode] [-I inode-size] [-J journal-options]
// [-G meta group size] [-N number-of-inodes]
// [-m reserved-blocks-percentage] [-o creator-os]
// [-g blocks-per-group] [-L volume-label] [-M last-mounted-directory]
// [-O feature[,...]] [-r fs-revision] [-E extended-option[,...]]
// [-T fs-type] [-U UUID] [-jnqvFSV] device [blocks-count]
//
// Options not commented below are taken but silently ignored:
enum { enum {
OPT_c = 1 << 0, OPT_c = 1 << 0,
OPT_l = 1 << 1, OPT_l = 1 << 1,
@ -159,15 +188,6 @@ enum {
//OPT_V = 1 << 25, // -V version. bbox applets don't support that //OPT_V = 1 << 25, // -V version. bbox applets don't support that
}; };
#define fd 3 /* predefined output descriptor */
static void PUT(uint64_t off, void *buf, uint32_t size)
{
// bb_info_msg("PUT[%llu]:[%u]", off, size);
xlseek(fd, off, SEEK_SET);
xwrite(fd, buf, size);
}
int mkfs_ext2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int mkfs_ext2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv) int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
{ {