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Date: Thu, 30 Aug 2007 12:12:31 -0700
From: Mingming Cao <cmm@...ibm.com>
To: Valerie Clement <valerie.clement@...l.net>
Cc: linux-ext4 <linux-ext4@...r.kernel.org>,
"Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH 3/8][e2fsprogs] add new -D <desc-size> option to mkfs
On Thu, 2007-08-30 at 17:37 +0200, Valerie Clement wrote:
> From: Valerie Clement <valerie.clement@...l.net>
>
> This patch adds a new option -D <descriptor-size> to mkfs to allow creating
> ext4 filesystems with larger group descriptor size.
>
> By default, the group descriptor size is 32 bytes.
> To support 64-bit physical block numbers and thus to be able to use filesystems
> > 16TB, the group descriptor size must be increased to 64 bytes.
>
Could you explain a bit more why we need this option? It seems to me we
could make the block group descriptor size to 64bytes whenever creating
a ext4 filesystem by default. Is there any case we need to create ext4
with old 32 bytes block group descriptors?
> Use mkfs -t ext4 -D 64 to create an ext4 filesystem with 64-byte group
> descriptor size. This set the EXT4_FEATURE_INCOMPAT_64BIT flag on device.
>
> The descriptor size is limited to a power-of-two value and to the block size.
>
> Signed-off-by: Valerie Clement <valerie.clement@...l.net>
> ---
>
> lib/ext2fs/ext2_fs.h | 7 +++++++
> lib/ext2fs/initialize.c | 1 +
> misc/mke2fs.c | 33 +++++++++++++++++++++++++++++++--
> 3 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
> index a316665..f6e8b36 100644
> --- a/lib/ext2fs/ext2_fs.h
> +++ b/lib/ext2fs/ext2_fs.h
> @@ -217,6 +217,13 @@ struct ext2_dx_countlimit {
> /*
> * Macro-instructions used to manage group descriptors
> */
> +#define EXT2_MIN_DESC_SIZE 32
> +#define EXT2_MIN_DESC_SIZE_64BIT 64
> +#define EXT2_MAX_DESC_SIZE EXT2_MIN_BLOCK_SIZE
> +#define EXT2_DESC_SIZE(s) \
> + ((EXT2_SB(s)->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) ? \
> + (s)->s_desc_size : EXT2_MIN_DESC_SIZE)
> +
> #define EXT2_BLOCKS_PER_GROUP(s) (EXT2_SB(s)->s_blocks_per_group)
> #define EXT2_INODES_PER_GROUP(s) (EXT2_SB(s)->s_inodes_per_group)
> #define EXT2_INODES_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s)/EXT2_INODE_SIZE(s))
> diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
> index 16e9eaa..ee7af93 100644
> --- a/lib/ext2fs/initialize.c
> +++ b/lib/ext2fs/initialize.c
> @@ -149,6 +149,7 @@ errcode_t ext2fs_initialize(const char *name, int flags,
>
> set_field(s_log_block_size, 0); /* default blocksize: 1024 bytes */
> set_field(s_log_frag_size, 0); /* default fragsize: 1024 bytes */
> + set_field(s_desc_size, 0);
> set_field(s_first_data_block, super->s_log_block_size ? 0 : 1);
> set_field(s_max_mnt_count, EXT2_DFL_MAX_MNT_COUNT);
> set_field(s_errors, EXT2_ERRORS_DEFAULT);
> diff --git a/misc/mke2fs.c b/misc/mke2fs.c
> index 4a6cace..115eef9 100644
> --- a/misc/mke2fs.c
> +++ b/misc/mke2fs.c
> @@ -96,7 +96,7 @@ static void usage(void)
> {
> fprintf(stderr, _("Usage: %s [-c|-t|-l filename] [-b block-size] "
> "[-f fragment-size]\n\t[-i bytes-per-inode] [-I inode-size] "
> - "[-j] [-J journal-options]\n"
> + "[-D descriptor-size] [-j] [-J journal-options]\n"
> "\t[-N number-of-inodes] [-m reserved-blocks-percentage] "
> "[-o creator-os]\n\t[-g blocks-per-group] [-L volume-label] "
> "[-M last-mounted-directory]\n\t[-O feature[,...]] "
> @@ -911,6 +911,7 @@ static void PRS(int argc, char *argv[])
> int blocksize = 0;
> int inode_ratio = 0;
> int inode_size = 0;
> + int desc_size = 0;
> double reserved_ratio = 5.0;
> int sector_size = 0;
> int show_version_only = 0;
> @@ -993,7 +994,7 @@ static void PRS(int argc, char *argv[])
> }
>
> while ((c = getopt (argc, argv,
> - "b:cf:g:i:jl:m:no:qr:s:tvE:FI:J:L:M:N:O:R:ST:V")) != EOF) {
> + "b:cf:g:i:jl:m:no:qr:s:tvD:E:FI:J:L:M:N:O:R:ST:V")) != EOF) {
> switch (c) {
> case 'b':
> blocksize = strtol(optarg, &tmp, 0);
> @@ -1110,6 +1111,14 @@ static void PRS(int argc, char *argv[])
> exit(1);
> }
> break;
> + case 'D':
> + desc_size = strtoul(optarg, &tmp, 0);
> + if (*tmp) {
> + com_err(program_name, 0,
> + _("invalid descriptor size - %s"), optarg);
> + exit(1);
> + }
> + break;
> case 'v':
> verbose = 1;
> break;
> @@ -1439,6 +1448,26 @@ static void PRS(int argc, char *argv[])
> }
> }
>
> + if (desc_size) {
> + if (desc_size < EXT2_MIN_DESC_SIZE ||
> + desc_size > EXT2_BLOCK_SIZE(&fs_param) ||
> + desc_size & (desc_size -1)) {
> + com_err(program_name, 0,
> + _("invalid descriptor size %d (min %d/max %d)"),
> + desc_size, EXT2_MIN_DESC_SIZE,
> + blocksize);
> + exit(1);
> + }
> + if (desc_size != EXT2_MIN_DESC_SIZE)
> + fprintf(stderr, _("Warning: %d-byte descriptors not "
> + "usable on older systems\n"),
> + desc_size);
> + fs_param.s_desc_size = desc_size;
> + if (desc_size > EXT2_MIN_DESC_SIZE)
> + fs_param.s_feature_incompat |= EXT4_FEATURE_INCOMPAT_64BIT;
> + }
> +
> +
> if (!force && fs_param.s_blocks_count >= ((unsigned) 1 << 31)) {
> com_err(program_name, 0,
> _("Filesystem too large. No more than 2**31-1 blocks\n"
>
>
> -
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