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Date: Fri, 7 Aug 2015 12:58:49 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Jan Kara <jack@...e.com>
Cc: linux-ext4@...r.kernel.org, Ted Tso <tytso@....edu>,
"Darrick J. Wong" <darrick.wong@...cle.com>
Subject: Re: [PATCH 13/19] tune2fs: Add support for changing number of reserved inodes
On Aug 7, 2015, at 4:51 AM, Jan Kara <jack@...e.com> wrote:
>
> Signed-off-by: Jan Kara <jack@...e.com>
> ---
> misc/tune2fs.8.in | 5 +++
> misc/tune2fs.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 107 insertions(+)
>
> diff --git a/misc/tune2fs.8.in b/misc/tune2fs.8.in
> index 4373fc49b255..922705329112 100644
> --- a/misc/tune2fs.8.in
> +++ b/misc/tune2fs.8.in
> @@ -236,6 +236,11 @@ program.
> This superblock setting is only honored in 2.6.35+ kernels;
> and not at all by the ext2 and ext3 file system drivers.
> .TP
> +.BI reserved_inodes= number_of_reserved_inodes
> +Set the number of inodes reserved for system files. This number must be
> +at least 10. Currently 10 is enough but future features may require additional
> +reserved inodes. Reserving more inodes requires full file system scan so it
> +can take a long time.
> .B test_fs
> Set a flag in the filesystem superblock indicating that it may be
> mounted using experimental kernel code, such as the ext4dev filesystem.
> diff --git a/misc/tune2fs.c b/misc/tune2fs.c
> index d6bfad3374d1..d6e75fe00814 100644
> --- a/misc/tune2fs.c
> +++ b/misc/tune2fs.c
> @@ -92,6 +92,7 @@ static char *features_cmd;
> static char *mntopts_cmd;
> static int stride, stripe_width;
> static int stride_set, stripe_width_set;
> +static unsigned long new_first_ino;
> static char *extended_cmd;
> static unsigned long new_inode_size;
> static char *ext_mount_opts;
> @@ -2298,6 +2299,34 @@ static int parse_extended_opts(ext2_filsys fs, const char *opts)
> continue;
> }
> ext_mount_opts = strdup(arg);
> + } else if (!strcmp(token, "reserved_inodes")) {
> + if (!arg) {
> + r_usage++;
> + continue;
> + }
> + new_first_ino = strtoul(arg, &p, 0);
> + if (*p) {
> + fprintf(stderr,
> + _("Invalid number of reserved inodes "
> + "%s\n"),
> + arg);
> + r_usage++;
> + continue;
> + }
> + /* Ino 0 is invalid so bump by 1... */
> + new_first_ino++;
> + if (new_first_ino < EXT2_GOOD_OLD_FIRST_INO) {
> + fprintf(stderr,
> + _("Too few reserved inodes "
> + "%s (must be at least %u)\n"),
> + arg, EXT2_GOOD_OLD_FIRST_INO - 1);
> + r_usage++;
> + continue;
> + }
> + /*
> + * Here should go further feature tests to disallow
> + * admin to free used system inode
> + */
Not only should this check that the new_first_ino isn't shrinking too
small to cover in-use special inodes, it should also verify that it
isn't growing to cover in-use normal inodes (e.g. lost+found).
I guess one option might be to reserve "12" for the lost+found inode,
since virtually all filesystems have it this way (though not all),
and it would also help e2fsck in the future if it didn't need to
allocate some other inode for lost+found in case of corruption.
Cheers, Andreas
> } else
> r_usage++;
> }
> @@ -2312,6 +2341,7 @@ static int parse_extended_opts(ext2_filsys fs, const char *opts)
> "\tmount_opts=<extended default mount options>\n"
> "\tstride=<RAID per-disk chunk size in blocks>\n"
> "\tstripe_width=<RAID stride*data disks in blocks>\n"
> + "\treserved_inodes=<number of reserved inodes>\n"
> "\ttest_fs\n"
> "\t^test_fs\n"));
> free(buf);
> @@ -2986,6 +3016,75 @@ fs_update_journal_user(struct ext2_super_block *sb, __u8 old_uuid[UUID_SIZE])
> return 0;
> }
>
> +/* Zero range of inodes and mark them as free / used */
> +static errcode_t zero_inodes_range(ext2_filsys fs, ext2_ino_t start,
> + ext2_ino_t end, int inuse)
> +{
> + char *inode;
> + int length = EXT2_INODE_SIZE(fs->super);
> + ext2_ino_t ino;
> + errcode_t retval;
> +
> + retval = ext2fs_get_memzero(length, &inode);
> + if (retval)
> + return retval;
> +
> + for (ino = start; ino <= end; ino++) {
> + ext2fs_inode_alloc_stats(fs, ino, inuse);
> + retval = ext2fs_write_inode_full(fs, ino,
> + (struct ext2_inode *)inode,
> + length);
> + if (retval)
> + break;
> + }
> + ext2fs_free_mem(inode);
> +
> + return retval;
> +}
> +
> +static errcode_t update_reserved_inodes(ext2_filsys fs)
> +{
> + errcode_t retval = 0;
> + ext2fs_inode_bitmap imap;
> + ext2_ino_t ino, first_ino = fs->super->s_first_ino;
> +
> + if (new_first_ino == first_ino)
> + return 0;
> +
> + /* Group descriptors will need writing as well */
> + fs->flags &= ~EXT2_FLAG_SUPER_ONLY;
> +
> + /* Freeing reserved inodes is easy */
> + if (new_first_ino < first_ino) {
> + retval = zero_inodes_range(fs, new_first_ino, first_ino - 1,
> + -1);
> + if (retval)
> + return retval;
> + goto out;
> + }
> +
> + retval = ext2fs_allocate_inode_bitmap(fs, "inodes to move", &imap);
> + if (retval)
> + return retval;
> +
> + for (ino = fs->super->s_first_ino; ino < new_first_ino; ino++)
> + ext2fs_mark_inode_bitmap2(imap, ino);
> +
> + retval = ext2fs_move_inodes(fs, imap);
> + ext2fs_free_inode_bitmap(imap);
> + if (retval)
> + return retval;
> +
> + retval = zero_inodes_range(fs, first_ino, new_first_ino - 1, +1);
> + if (retval)
> + return retval;
> +out:
> + fs->super->s_first_ino = new_first_ino;
> + ext2fs_mark_super_dirty(fs);
> +
> + return 0;
> +}
> +
> int main(int argc, char **argv)
> {
> errcode_t retval;
> @@ -3404,6 +3503,9 @@ retry_open:
> if (feature_64bit)
> convert_64bit(&fs, feature_64bit);
>
> + if (new_first_ino)
> + update_reserved_inodes(fs);
> +
> if (rewrite_checksums)
> rewrite_metadata_checksums(fs);
>
> --
> 2.1.4
>
> --
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Cheers, Andreas
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