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authorDenys Vlasenko <vda.linux@googlemail.com>2009-10-21 09:34:32 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2009-10-21 09:34:32 (GMT)
commit2ee2724a41f195f8a5e3e4e9ebc54dadc255d6f7 (patch)
treeb3b973095c4b77b0ff48a3c113138ca747d1f4fc
parent2288d86a54eee81800bdadea6f603ad4e234efb1 (diff)
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mkfs_ext2: explain 256-byte inodes. no code changes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--util-linux/mkfs_ext2.c58
1 files changed, 39 insertions, 19 deletions
diff --git a/util-linux/mkfs_ext2.c b/util-linux/mkfs_ext2.c
index de4c8b6..5cd9238 100644
--- a/util-linux/mkfs_ext2.c
+++ b/util-linux/mkfs_ext2.c
@@ -120,16 +120,45 @@ static uint32_t has_super(uint32_t x)
}
}
-/* 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]
-*/
-// N.B. not commented below options are taken and silently ignored
+#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);
+}
+
+// 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 {
OPT_c = 1 << 0,
OPT_l = 1 << 1,
@@ -159,15 +188,6 @@ enum {
//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 UNUSED_PARAM, char **argv)
{