* Re: patch to support ext4 online resizing with meta block groups
[not found] <f4ca31560706271157p2a25546fmf8fad29dfcf8f056@mail.gmail.com>
@ 2007-06-28 6:12 ` Andreas Dilger
0 siblings, 0 replies; only message in thread
From: Andreas Dilger @ 2007-06-28 6:12 UTC (permalink / raw)
To: zuogui xie; +Cc: linux-ext4
On Jun 27, 2007 19:57 +0100, zuogui xie wrote:
> To keep compatibility, we begin to use meta block groups after the
> reserved block groups run out. superblock and single block group descriptor
> block are placed at the beginning of the first, second, and last block
> groups in a meta-block group. The block group in the meta block groups
> no longer reserves the blocks for group descriptor table. To let it work,
> we need mkfs.ext3 to set superblock's s_first_meta_bg field and it is easy
> to implement.
Do we really need mkfs.ext3 to do that? It can easily be done by the
kernel when resizing the filesystem beyond the last group descriptor
block. It would also set the INCOMPAT_META_BG feature flag, which has
been in kernels for a long time now (at least back to 2.4.29 or so), so
only a small danger of incompatibility. There should probably be support
in resize2fs or similar to be able to remove the META_BG feature to return
the filesystem to "normal" if this is needed.
> --- linux-2.6.21.5/fs/ext4/resize.c 2007-06-11 19:37:06.000000000 +0100
> +++ resize.c 2007-06-27 10:55:14.000000000 +0100
> @@ -21,6 +21,25 @@
> #define outside(b, first, last) ((b) < (first) || (b) >= (last))
> #define inside(b, first, last) ((b) >= (first) && (b) < (last))
>
> +/**
> + * ext4_bg_in_metabg - whether this block group is in meta block group
> + * @sb: superblock for filesystem
> + * @group: group number to check
> + *
> + * Return value will be only 0 or 1.
> + */
> +int ext4_bg_in_metabg(struct super_block *sb, int group)
> +{
> + unsigned long first_meta_bg =
> + le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
> + unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
Your mailer seems to have broken all of the whitespace in this patch.
> @@ -171,8 +190,11 @@ static int setup_new_group_blocks(struct
> + /*The group in meta block group no longer reserves blocks */
Space before "The".
> @@ -203,8 +225,9 @@ static int setup_new_group_blocks(struct
> + for (i = 0, bit = 1, block = start +
> + ext4_bg_has_super(sb, input->group);i < gdblocks;
Space before "i".
> @@ -219,7 +242,23 @@ static int setup_new_group_blocks(struct
> + if(bg_in_metabg) {
Space after "if".
> + unsigned long last = first + EXT4_DESC_PER_BLOCK(sb) -
> + 1;
Can probably fit "1;" on previous line by removing space around '-'.
> +static int add_new_gdb_meta(handle_t *handle, struct inode *inode,
> + struct ext4_new_group_data *input,
> + struct buffer_head **primary)
> +{
> + n_group_desc[gdb_num] = *primary;
> + EXT4_SB(sb)->s_group_desc = n_group_desc;
> + EXT4_SB(sb)->s_gdb_count++;
> + kfree(o_group_desc);
This should save the s_first_metabg and set INCOMPAT_META_BG if it is
the first such group.
> +static void update_backups_metabg(struct super_block *sb,
> + int gdb_num, char *data, int size)
> +{
> + struct ext4_sb_info *sbi = EXT4_SB(sb);
> +
Remove empty line here.
> + unsigned second_bg_no = gdb_num * EXT4_DESC_PER_BLOCK(sb) + 1;
> + unsigned last_bg_no = second_bg_no + EXT4_DESC_PER_BLOCK(sb) -2;
> + unsigned list_bg_no[2]={second_bg_no,last_bg_no};
Please don't use these extra variables, just initialize list_bg_no[]
directly.
> + int i=0;
Spaces around '='.
> +
Remove empty line here.
> + int rest = sb->s_blocksize - size;
> + handle_t *handle;
> + int err = 0, err2;
> + unsigned group=0;
Spaces around '='
> + struct buffer_head *bh;
> + group=list_bg_no[i];
Space around '='.
> @@ -813,8 +1012,13 @@ int ext4_group_add(struct super_block *s
> if (reserved_gdb && ext4_bg_num_gdb(sb, input->group) &&
> (err = reserve_backup_gdb(handle, inode, input)))
> goto exit_journal;
> - } else if ((err = add_new_gdb(handle, inode, input, &primary)))
> + } else if (!ext4_bg_in_metabg(sb, input->group) &&
> + (err = add_new_gdb(handle, inode, input, &primary))) {
> + goto exit_journal;
> + } else if (ext4_bg_in_metabg(sb, input->group) &&
Use "bg_in_metabg" here.
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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