Patchwork [6/6] resize2fs: Convert fs to and from 64bit mode

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Submitter Darrick J. Wong
Date Aug. 29, 2013, 12:44 a.m.
Message ID <20130829004423.3190.78720.stgit@blackbox.djwong.org>
Download mbox | patch
Permalink /patch/270659/
State New
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Comments

Darrick J. Wong - Aug. 29, 2013, 12:44 a.m.
resize2fs does its magic by loading a filesystem, duplicating the in-memory
image of that fs, moving relevant blocks out of the way of whatever new
metadata get created, and finally writing everything back out to disk.
Enabling 64bit mode enlarges the group descriptors, which makes resize2fs a
reasonable vehicle for taking care of the rest of the bookkeeping requirements,
so add to resize2fs the ability to convert a filesystem to 64bit mode and back.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 resize/main.c         |   22 ++++
 resize/resize2fs.8.in |   18 +++
 resize/resize2fs.c    |  264 ++++++++++++++++++++++++++++++++++++++++++++++++-
 resize/resize2fs.h    |    3 +
 4 files changed, 300 insertions(+), 7 deletions(-)



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Darrick J. Wong - Sept. 9, 2013, 5:29 p.m.
Found some bugs in this; I'll repost the series (without the patches Ted just
merged) in a few days.

--D

On Wed, Aug 28, 2013 at 05:44:23PM -0700, Darrick J. Wong wrote:
> resize2fs does its magic by loading a filesystem, duplicating the in-memory
> image of that fs, moving relevant blocks out of the way of whatever new
> metadata get created, and finally writing everything back out to disk.
> Enabling 64bit mode enlarges the group descriptors, which makes resize2fs a
> reasonable vehicle for taking care of the rest of the bookkeeping requirements,
> so add to resize2fs the ability to convert a filesystem to 64bit mode and back.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  resize/main.c         |   22 ++++
>  resize/resize2fs.8.in |   18 +++
>  resize/resize2fs.c    |  264 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  resize/resize2fs.h    |    3 +
>  4 files changed, 300 insertions(+), 7 deletions(-)
> 
> 
> diff --git a/resize/main.c b/resize/main.c
> index b648a15..f353351 100644
> --- a/resize/main.c
> +++ b/resize/main.c
> @@ -41,7 +41,7 @@ char *program_name, *device_name, *io_options;
>  static void usage (char *prog)
>  {
>  	fprintf (stderr, _("Usage: %s [-d debug_flags] [-f] [-F] [-M] [-P] "
> -			   "[-p] device [new_size]\n\n"), prog);
> +			   "[-p] device [-b|-s|new_size]\n\n"), prog);
>  
>  	exit (1);
>  }
> @@ -199,7 +199,7 @@ int main (int argc, char ** argv)
>  	if (argc && *argv)
>  		program_name = *argv;
>  
> -	while ((c = getopt (argc, argv, "d:fFhMPpS:")) != EOF) {
> +	while ((c = getopt(argc, argv, "d:fFhMPpS:bs")) != EOF) {
>  		switch (c) {
>  		case 'h':
>  			usage(program_name);
> @@ -225,6 +225,12 @@ int main (int argc, char ** argv)
>  		case 'S':
>  			use_stride = atoi(optarg);
>  			break;
> +		case 'b':
> +			flags |= RESIZE_ENABLE_64BIT;
> +			break;
> +		case 's':
> +			flags |= RESIZE_DISABLE_64BIT;
> +			break;
>  		default:
>  			usage(program_name);
>  		}
> @@ -434,7 +440,17 @@ int main (int argc, char ** argv)
>  			fs->blocksize / 1024, new_size);
>  		exit(1);
>  	}
> -	if (new_size == ext2fs_blocks_count(fs->super)) {
> +	if (flags & RESIZE_DISABLE_64BIT && flags & RESIZE_ENABLE_64BIT) {
> +		fprintf(stderr, _("Cannot set and unset 64bit feature.\n"));
> +		exit(1);
> +	} else if (flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)) {
> +		new_size = ext2fs_blocks_count(fs->super);
> +		if (new_size >= (1ULL << 32)) {
> +			fprintf(stderr, _("Cannot change 64bit on a filesystem"
> +				" that is larger than 2^32 blocks.\n"));
> +			exit(1);
> +		}
> +	} else if (new_size == ext2fs_blocks_count(fs->super)) {
>  		fprintf(stderr, _("The filesystem is already %llu blocks "
>  			"long.  Nothing to do!\n\n"), new_size);
>  		exit(0);
> diff --git a/resize/resize2fs.8.in b/resize/resize2fs.8.in
> index 735fc91..d6deee6 100644
> --- a/resize/resize2fs.8.in
> +++ b/resize/resize2fs.8.in
> @@ -8,7 +8,7 @@ resize2fs \- ext2/ext3/ext4 file system resizer
>  .SH SYNOPSIS
>  .B resize2fs
>  [
> -.B \-fFpPM
> +.B \-fFpPMbs
>  ]
>  [
>  .B \-d
> @@ -85,8 +85,21 @@ to shrink the size of filesystem.  Then you may use
>  to shrink the size of the partition.  When shrinking the size of
>  the partition, make sure you do not make it smaller than the new size
>  of the ext2 filesystem!
> +.PP
> +The
> +.B \-b
> +and
> +.B \-s
> +options enable and disable the 64bit feature, respectively.  The resize2fs
> +program will, of course, take care of resizing the block group descriptors
> +and moving other data blocks out of the way, as needed.  It is not possible
> +to resize the filesystem concurrent with changing the 64bit status.
>  .SH OPTIONS
>  .TP
> +.B \-b
> +Turns on the 64bit feature, resizes the group descriptors as necessary, and
> +moves other metadata out of the way.
> +.TP
>  .B \-d \fIdebug-flags
>  Turns on various resize2fs debugging features, if they have been compiled
>  into the binary.
> @@ -124,6 +137,9 @@ of what the program is doing.
>  .B \-P
>  Print the minimum size of the filesystem and exit.
>  .TP
> +.B \-s
> +Turns off the 64bit feature and frees blocks that are no longer in use.
> +.TP
>  .B \-S \fIRAID-stride
>  The
>  .B resize2fs
> diff --git a/resize/resize2fs.c b/resize/resize2fs.c
> index 76d7aa6..fa7f99e 100644
> --- a/resize/resize2fs.c
> +++ b/resize/resize2fs.c
> @@ -53,6 +53,9 @@ static errcode_t ext2fs_calculate_summary_stats(ext2_filsys fs);
>  static errcode_t fix_sb_journal_backup(ext2_filsys fs);
>  static errcode_t mark_table_blocks(ext2_filsys fs,
>  				   ext2fs_block_bitmap bmap);
> +static errcode_t resize_group_descriptors(ext2_resize_t rfs, blk64_t new_size);
> +static errcode_t move_bg_metadata(ext2_resize_t rfs);
> +static errcode_t zero_high_bits_in_inodes(ext2_filsys fs);
>  
>  /*
>   * Some helper CPP macros
> @@ -119,13 +122,30 @@ errcode_t resize_fs(ext2_filsys fs, blk64_t *new_size, int flags,
>  	if (retval)
>  		goto errout;
>  
> +	init_resource_track(&rtrack, "resize_group_descriptors", fs->io);
> +	retval = resize_group_descriptors(rfs, *new_size);
> +	if (retval)
> +		goto errout;
> +	print_resource_track(rfs, &rtrack, fs->io);
> +
> +	init_resource_track(&rtrack, "move_bg_metadata", fs->io);
> +	retval = move_bg_metadata(rfs);
> +	if (retval)
> +		goto errout;
> +	print_resource_track(rfs, &rtrack, fs->io);
> +
> +	init_resource_track(&rtrack, "zero_high_bits_in_metadata", fs->io);
> +	retval = zero_high_bits_in_inodes(rfs->new_fs);
> +	if (retval)
> +		goto errout;
> +	print_resource_track(rfs, &rtrack, fs->io);
> +
>  	init_resource_track(&rtrack, "adjust_superblock", fs->io);
>  	retval = adjust_superblock(rfs, *new_size);
>  	if (retval)
>  		goto errout;
>  	print_resource_track(rfs, &rtrack, fs->io);
>  
> -
>  	init_resource_track(&rtrack, "fix_uninit_block_bitmaps 2", fs->io);
>  	fix_uninit_block_bitmaps(rfs->new_fs);
>  	print_resource_track(rfs, &rtrack, fs->io);
> @@ -221,6 +241,241 @@ errout:
>  	return retval;
>  }
>  
> +/* Toggle 64bit mode */
> +static errcode_t resize_group_descriptors(ext2_resize_t rfs, blk64_t new_size)
> +{
> +	void *o, *n, *new_group_desc;
> +	dgrp_t i;
> +	int copy_size;
> +	errcode_t retval;
> +
> +	if (!(rfs->flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)))
> +		return 0;
> +
> +	if (new_size != ext2fs_blocks_count(rfs->new_fs->super) ||
> +	    ext2fs_blocks_count(rfs->new_fs->super) >= (1ULL << 32) ||
> +	    (rfs->flags & RESIZE_DISABLE_64BIT &&
> +	     rfs->flags & RESIZE_ENABLE_64BIT))
> +		return EXT2_ET_INVALID_ARGUMENT;
> +
> +	if (rfs->flags & RESIZE_DISABLE_64BIT) {
> +		rfs->new_fs->super->s_feature_incompat &=
> +				~EXT4_FEATURE_INCOMPAT_64BIT;
> +		rfs->new_fs->super->s_desc_size = EXT2_MIN_DESC_SIZE;
> +	} else if (rfs->flags & RESIZE_ENABLE_64BIT) {
> +		rfs->new_fs->super->s_feature_incompat |=
> +				EXT4_FEATURE_INCOMPAT_64BIT;
> +		rfs->new_fs->super->s_desc_size = EXT2_MIN_DESC_SIZE_64BIT;
> +	}
> +
> +	if (EXT2_DESC_SIZE(rfs->old_fs->super) ==
> +	    EXT2_DESC_SIZE(rfs->new_fs->super))
> +		return 0;
> +
> +	o = rfs->new_fs->group_desc;
> +	rfs->new_fs->desc_blocks = ext2fs_div_ceil(
> +			rfs->old_fs->group_desc_count,
> +			EXT2_DESC_PER_BLOCK(rfs->new_fs->super));
> +	retval = ext2fs_get_arrayzero(rfs->new_fs->desc_blocks,
> +				      rfs->old_fs->blocksize, &new_group_desc);
> +	if (retval)
> +		return retval;
> +
> +	n = new_group_desc;
> +
> +	if (EXT2_DESC_SIZE(rfs->old_fs->super) <=
> +	    EXT2_DESC_SIZE(rfs->new_fs->super))
> +		copy_size = EXT2_DESC_SIZE(rfs->old_fs->super);
> +	else
> +		copy_size = EXT2_DESC_SIZE(rfs->new_fs->super);
> +	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
> +		memcpy(n, o, copy_size);
> +		n += EXT2_DESC_SIZE(rfs->new_fs->super);
> +		o += EXT2_DESC_SIZE(rfs->old_fs->super);
> +	}
> +
> +	ext2fs_free_mem(&rfs->new_fs->group_desc);
> +	rfs->new_fs->group_desc = new_group_desc;
> +
> +	for (i = 0; i < rfs->old_fs->group_desc_count; i++)
> +		ext2fs_group_desc_csum_set(rfs->new_fs, i);
> +
> +	return 0;
> +}
> +
> +/* Move bitmaps/inode tables out of the way. */
> +static errcode_t move_bg_metadata(ext2_resize_t rfs)
> +{
> +	dgrp_t i;
> +	blk64_t b, c, d;
> +	ext2fs_block_bitmap old_map, new_map;
> +	int old, new;
> +	errcode_t retval;
> +	int zero = 0, one = 1;
> +
> +	if (!(rfs->flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)))
> +		return 0;
> +
> +	retval = ext2fs_allocate_block_bitmap(rfs->old_fs, "oldfs", &old_map);
> +	if (retval)
> +		return retval;
> +
> +	retval = ext2fs_allocate_block_bitmap(rfs->new_fs, "newfs", &new_map);
> +	if (retval)
> +		goto out;
> +
> +	/* Construct bitmaps of super/descriptor blocks in old and new fs */
> +	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
> +		retval = ext2fs_super_and_bgd_loc2(rfs->old_fs, i, &b, &c, &d,
> +						   NULL);
> +		if (retval)
> +			goto out;
> +		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, b));
> +		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, c));
> +		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, d));
> +
> +		retval = ext2fs_super_and_bgd_loc2(rfs->new_fs, i, &b, &c, &d,
> +						   NULL);
> +		if (retval)
> +			goto out;
> +		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, b));
> +		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, c));
> +		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, d));
> +	}
> +
> +	/* Find changes in block allocations for bg metadata */
> +	for (b = 0; b < ext2fs_blocks_count(rfs->new_fs->super); b++) {
> +		c = EXT2FS_B2C(rfs->new_fs, b);
> +		old = ext2fs_test_block_bitmap2(old_map, c);
> +		new = ext2fs_test_block_bitmap2(new_map, c);
> +
> +		if (old && !new)
> +			ext2fs_unmark_block_bitmap2(rfs->new_fs->block_map, c);
> +		else if (!old && new)
> +			; /* empty ext2fs_mark_block_bitmap2(new_map, c); */
> +		else
> +			ext2fs_unmark_block_bitmap2(new_map, c);
> +	}
> +	/* new_map now shows blocks that have been newly allocated. */
> +
> +	/* Move any conflicting bitmaps and inode tables */
> +	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
> +		b = EXT2FS_B2C(rfs->new_fs,
> +			       ext2fs_block_bitmap_loc(rfs->new_fs, i));
> +		if (ext2fs_test_block_bitmap2(new_map, b))
> +			ext2fs_block_bitmap_loc_set(rfs->new_fs, i, 0);
> +
> +		b = EXT2FS_B2C(rfs->new_fs,
> +			       ext2fs_inode_bitmap_loc(rfs->new_fs, i));
> +		if (ext2fs_test_block_bitmap2(new_map, b))
> +			ext2fs_inode_bitmap_loc_set(rfs->new_fs, i, 0);
> +
> +		c = ext2fs_inode_table_loc(rfs->new_fs, i);
> +		for (b = 0; b < rfs->new_fs->inode_blocks_per_group; b++) {
> +			if (ext2fs_test_block_bitmap2(new_map, b + c)) {
> +				ext2fs_inode_table_loc_set(rfs->new_fs, i, 0);
> +				break;
> +			}
> +		}
> +	}
> +
> +out:
> +	if (old_map)
> +		ext2fs_free_block_bitmap(old_map);
> +	if (new_map)
> +		ext2fs_free_block_bitmap(new_map);
> +	return retval;
> +}
> +
> +/* Zero out the high bits of extent fields */
> +static errcode_t zero_high_bits_in_extents(ext2_filsys fs, ext2_ino_t ino,
> +				 struct ext2_inode *inode)
> +{
> +	ext2_extent_handle_t	handle;
> +	struct ext2fs_extent	extent;
> +	int			op = EXT2_EXTENT_ROOT;
> +	errcode_t		errcode;
> +
> +	if (!(inode->i_flags & EXT4_EXTENTS_FL))
> +		return 0;
> +
> +	errcode = ext2fs_extent_open(fs, ino, &handle);
> +	if (errcode)
> +		return errcode;
> +
> +	while (1) {
> +		errcode = ext2fs_extent_get(handle, op, &extent);
> +		if (errcode)
> +			break;
> +
> +		op = EXT2_EXTENT_NEXT_SIB;
> +
> +		extent.e_pblk &= 0xFFFFFFFF;
> +		errcode = ext2fs_extent_replace(handle, 0, &extent);
> +		if (errcode)
> +			break;
> +	}
> +
> +	/* Ok if we run off the end */
> +	if (errcode == EXT2_ET_EXTENT_NO_NEXT)
> +		errcode = 0;
> +	return errcode;
> +}
> +
> +/* Zero out the high bits of inodes. */
> +static errcode_t zero_high_bits_in_inodes(ext2_filsys fs)
> +{
> +	int length = EXT2_INODE_SIZE(fs->super);
> +	struct ext2_inode *inode = NULL;
> +	ext2_inode_scan	scan = NULL;
> +	errcode_t	retval;
> +	ext2_ino_t	ino;
> +	blk64_t		file_acl_block;
> +	__u32		sz_mask_high;
> +	int		inode_dirty;
> +
> +	if (fs->super->s_creator_os != EXT2_OS_LINUX)
> +		return 0;
> +
> +	retval = ext2fs_open_inode_scan(fs, 0, &scan);
> +	if (retval)
> +		return retval;
> +
> +	retval = ext2fs_get_mem(length, &inode);
> +	if (retval)
> +		goto out;
> +
> +	sz_mask_high = (((1ULL << 32) * EXT2_BLOCK_SIZE(fs->super)) - 1) >> 32;
> +	do {
> +		retval = ext2fs_get_next_inode_full(scan, &ino, inode, length);
> +		if (retval)
> +			goto out;
> +		if (!ino)
> +			break;
> +		if (!ext2fs_test_inode_bitmap2(fs->inode_map, ino))
> +			continue;
> +
> +		inode->i_size_high &= sz_mask_high;
> +		inode->osd2.linux2.l_i_blocks_hi = 0;
> +		inode->osd2.linux2.l_i_file_acl_high = 0;
> +
> +		retval = ext2fs_write_inode_full(fs, ino, inode,
> +						 length);
> +		if (retval)
> +			goto out;
> +
> +		retval = zero_high_bits_in_extents(fs, ino, inode);
> +		if (retval)
> +			goto out;
> +	} while (ino);
> +
> +out:
> +	if (inode)
> +		ext2fs_free_mem(&inode);
> +	if (scan)
> +		ext2fs_close_inode_scan(scan);
> +}
> +
>  /*
>   * Clean up the bitmaps for unitialized bitmaps
>   */
> @@ -424,7 +679,8 @@ retry:
>  	/*
>  	 * Reallocate the group descriptors as necessary.
>  	 */
> -	if (old_fs->desc_blocks != fs->desc_blocks) {
> +	if (EXT2_DESC_SIZE(old_fs->super) == EXT2_DESC_SIZE(fs->super) &&
> +	    old_fs->desc_blocks != fs->desc_blocks) {
>  		retval = ext2fs_resize_mem(old_fs->desc_blocks *
>  					   fs->blocksize,
>  					   fs->desc_blocks * fs->blocksize,
> @@ -939,7 +1195,9 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
>  		new_blocks = fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
>  	}
>  
> -	if (old_blocks == new_blocks) {
> +	if (EXT2_DESC_SIZE(rfs->old_fs->super) ==
> +	    EXT2_DESC_SIZE(rfs->new_fs->super) &&
> +	    old_blocks == new_blocks) {
>  		retval = 0;
>  		goto errout;
>  	}
> diff --git a/resize/resize2fs.h b/resize/resize2fs.h
> index d425491..e24319d 100644
> --- a/resize/resize2fs.h
> +++ b/resize/resize2fs.h
> @@ -81,6 +81,9 @@ typedef struct ext2_sim_progress *ext2_sim_progmeter;
>  #define RESIZE_PERCENT_COMPLETE		0x0100
>  #define RESIZE_VERBOSE			0x0200
>  
> +#define RESIZE_ENABLE_64BIT		0x0400
> +#define RESIZE_DISABLE_64BIT		0x0800
> +
>  /*
>   * This structure is used for keeping track of how much resources have
>   * been used for a particular resize2fs pass.
> 
> --
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Theodore Ts'o - Sept. 9, 2013, 5:47 p.m.
On Mon, Sep 09, 2013 at 10:29:44AM -0700, Darrick J. Wong wrote:
> Found some bugs in this; I'll repost the series (without the patches Ted just
> merged) in a few days.

Patches 1 and 2 were merged into the maint branch.  I will review and
merge patches 3-5 into the 1.43 branches (master/next), and I'll hold
off on patch #6.

Cheers,

						- Ted
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Patch

diff --git a/resize/main.c b/resize/main.c
index b648a15..f353351 100644
--- a/resize/main.c
+++ b/resize/main.c
@@ -41,7 +41,7 @@  char *program_name, *device_name, *io_options;
 static void usage (char *prog)
 {
 	fprintf (stderr, _("Usage: %s [-d debug_flags] [-f] [-F] [-M] [-P] "
-			   "[-p] device [new_size]\n\n"), prog);
+			   "[-p] device [-b|-s|new_size]\n\n"), prog);
 
 	exit (1);
 }
@@ -199,7 +199,7 @@  int main (int argc, char ** argv)
 	if (argc && *argv)
 		program_name = *argv;
 
-	while ((c = getopt (argc, argv, "d:fFhMPpS:")) != EOF) {
+	while ((c = getopt(argc, argv, "d:fFhMPpS:bs")) != EOF) {
 		switch (c) {
 		case 'h':
 			usage(program_name);
@@ -225,6 +225,12 @@  int main (int argc, char ** argv)
 		case 'S':
 			use_stride = atoi(optarg);
 			break;
+		case 'b':
+			flags |= RESIZE_ENABLE_64BIT;
+			break;
+		case 's':
+			flags |= RESIZE_DISABLE_64BIT;
+			break;
 		default:
 			usage(program_name);
 		}
@@ -434,7 +440,17 @@  int main (int argc, char ** argv)
 			fs->blocksize / 1024, new_size);
 		exit(1);
 	}
-	if (new_size == ext2fs_blocks_count(fs->super)) {
+	if (flags & RESIZE_DISABLE_64BIT && flags & RESIZE_ENABLE_64BIT) {
+		fprintf(stderr, _("Cannot set and unset 64bit feature.\n"));
+		exit(1);
+	} else if (flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)) {
+		new_size = ext2fs_blocks_count(fs->super);
+		if (new_size >= (1ULL << 32)) {
+			fprintf(stderr, _("Cannot change 64bit on a filesystem"
+				" that is larger than 2^32 blocks.\n"));
+			exit(1);
+		}
+	} else if (new_size == ext2fs_blocks_count(fs->super)) {
 		fprintf(stderr, _("The filesystem is already %llu blocks "
 			"long.  Nothing to do!\n\n"), new_size);
 		exit(0);
diff --git a/resize/resize2fs.8.in b/resize/resize2fs.8.in
index 735fc91..d6deee6 100644
--- a/resize/resize2fs.8.in
+++ b/resize/resize2fs.8.in
@@ -8,7 +8,7 @@  resize2fs \- ext2/ext3/ext4 file system resizer
 .SH SYNOPSIS
 .B resize2fs
 [
-.B \-fFpPM
+.B \-fFpPMbs
 ]
 [
 .B \-d
@@ -85,8 +85,21 @@  to shrink the size of filesystem.  Then you may use
 to shrink the size of the partition.  When shrinking the size of
 the partition, make sure you do not make it smaller than the new size
 of the ext2 filesystem!
+.PP
+The
+.B \-b
+and
+.B \-s
+options enable and disable the 64bit feature, respectively.  The resize2fs
+program will, of course, take care of resizing the block group descriptors
+and moving other data blocks out of the way, as needed.  It is not possible
+to resize the filesystem concurrent with changing the 64bit status.
 .SH OPTIONS
 .TP
+.B \-b
+Turns on the 64bit feature, resizes the group descriptors as necessary, and
+moves other metadata out of the way.
+.TP
 .B \-d \fIdebug-flags
 Turns on various resize2fs debugging features, if they have been compiled
 into the binary.
@@ -124,6 +137,9 @@  of what the program is doing.
 .B \-P
 Print the minimum size of the filesystem and exit.
 .TP
+.B \-s
+Turns off the 64bit feature and frees blocks that are no longer in use.
+.TP
 .B \-S \fIRAID-stride
 The
 .B resize2fs
diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 76d7aa6..fa7f99e 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -53,6 +53,9 @@  static errcode_t ext2fs_calculate_summary_stats(ext2_filsys fs);
 static errcode_t fix_sb_journal_backup(ext2_filsys fs);
 static errcode_t mark_table_blocks(ext2_filsys fs,
 				   ext2fs_block_bitmap bmap);
+static errcode_t resize_group_descriptors(ext2_resize_t rfs, blk64_t new_size);
+static errcode_t move_bg_metadata(ext2_resize_t rfs);
+static errcode_t zero_high_bits_in_inodes(ext2_filsys fs);
 
 /*
  * Some helper CPP macros
@@ -119,13 +122,30 @@  errcode_t resize_fs(ext2_filsys fs, blk64_t *new_size, int flags,
 	if (retval)
 		goto errout;
 
+	init_resource_track(&rtrack, "resize_group_descriptors", fs->io);
+	retval = resize_group_descriptors(rfs, *new_size);
+	if (retval)
+		goto errout;
+	print_resource_track(rfs, &rtrack, fs->io);
+
+	init_resource_track(&rtrack, "move_bg_metadata", fs->io);
+	retval = move_bg_metadata(rfs);
+	if (retval)
+		goto errout;
+	print_resource_track(rfs, &rtrack, fs->io);
+
+	init_resource_track(&rtrack, "zero_high_bits_in_metadata", fs->io);
+	retval = zero_high_bits_in_inodes(rfs->new_fs);
+	if (retval)
+		goto errout;
+	print_resource_track(rfs, &rtrack, fs->io);
+
 	init_resource_track(&rtrack, "adjust_superblock", fs->io);
 	retval = adjust_superblock(rfs, *new_size);
 	if (retval)
 		goto errout;
 	print_resource_track(rfs, &rtrack, fs->io);
 
-
 	init_resource_track(&rtrack, "fix_uninit_block_bitmaps 2", fs->io);
 	fix_uninit_block_bitmaps(rfs->new_fs);
 	print_resource_track(rfs, &rtrack, fs->io);
@@ -221,6 +241,241 @@  errout:
 	return retval;
 }
 
+/* Toggle 64bit mode */
+static errcode_t resize_group_descriptors(ext2_resize_t rfs, blk64_t new_size)
+{
+	void *o, *n, *new_group_desc;
+	dgrp_t i;
+	int copy_size;
+	errcode_t retval;
+
+	if (!(rfs->flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)))
+		return 0;
+
+	if (new_size != ext2fs_blocks_count(rfs->new_fs->super) ||
+	    ext2fs_blocks_count(rfs->new_fs->super) >= (1ULL << 32) ||
+	    (rfs->flags & RESIZE_DISABLE_64BIT &&
+	     rfs->flags & RESIZE_ENABLE_64BIT))
+		return EXT2_ET_INVALID_ARGUMENT;
+
+	if (rfs->flags & RESIZE_DISABLE_64BIT) {
+		rfs->new_fs->super->s_feature_incompat &=
+				~EXT4_FEATURE_INCOMPAT_64BIT;
+		rfs->new_fs->super->s_desc_size = EXT2_MIN_DESC_SIZE;
+	} else if (rfs->flags & RESIZE_ENABLE_64BIT) {
+		rfs->new_fs->super->s_feature_incompat |=
+				EXT4_FEATURE_INCOMPAT_64BIT;
+		rfs->new_fs->super->s_desc_size = EXT2_MIN_DESC_SIZE_64BIT;
+	}
+
+	if (EXT2_DESC_SIZE(rfs->old_fs->super) ==
+	    EXT2_DESC_SIZE(rfs->new_fs->super))
+		return 0;
+
+	o = rfs->new_fs->group_desc;
+	rfs->new_fs->desc_blocks = ext2fs_div_ceil(
+			rfs->old_fs->group_desc_count,
+			EXT2_DESC_PER_BLOCK(rfs->new_fs->super));
+	retval = ext2fs_get_arrayzero(rfs->new_fs->desc_blocks,
+				      rfs->old_fs->blocksize, &new_group_desc);
+	if (retval)
+		return retval;
+
+	n = new_group_desc;
+
+	if (EXT2_DESC_SIZE(rfs->old_fs->super) <=
+	    EXT2_DESC_SIZE(rfs->new_fs->super))
+		copy_size = EXT2_DESC_SIZE(rfs->old_fs->super);
+	else
+		copy_size = EXT2_DESC_SIZE(rfs->new_fs->super);
+	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
+		memcpy(n, o, copy_size);
+		n += EXT2_DESC_SIZE(rfs->new_fs->super);
+		o += EXT2_DESC_SIZE(rfs->old_fs->super);
+	}
+
+	ext2fs_free_mem(&rfs->new_fs->group_desc);
+	rfs->new_fs->group_desc = new_group_desc;
+
+	for (i = 0; i < rfs->old_fs->group_desc_count; i++)
+		ext2fs_group_desc_csum_set(rfs->new_fs, i);
+
+	return 0;
+}
+
+/* Move bitmaps/inode tables out of the way. */
+static errcode_t move_bg_metadata(ext2_resize_t rfs)
+{
+	dgrp_t i;
+	blk64_t b, c, d;
+	ext2fs_block_bitmap old_map, new_map;
+	int old, new;
+	errcode_t retval;
+	int zero = 0, one = 1;
+
+	if (!(rfs->flags & (RESIZE_DISABLE_64BIT | RESIZE_ENABLE_64BIT)))
+		return 0;
+
+	retval = ext2fs_allocate_block_bitmap(rfs->old_fs, "oldfs", &old_map);
+	if (retval)
+		return retval;
+
+	retval = ext2fs_allocate_block_bitmap(rfs->new_fs, "newfs", &new_map);
+	if (retval)
+		goto out;
+
+	/* Construct bitmaps of super/descriptor blocks in old and new fs */
+	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
+		retval = ext2fs_super_and_bgd_loc2(rfs->old_fs, i, &b, &c, &d,
+						   NULL);
+		if (retval)
+			goto out;
+		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, b));
+		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, c));
+		ext2fs_mark_block_bitmap2(old_map, EXT2FS_B2C(rfs->old_fs, d));
+
+		retval = ext2fs_super_and_bgd_loc2(rfs->new_fs, i, &b, &c, &d,
+						   NULL);
+		if (retval)
+			goto out;
+		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, b));
+		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, c));
+		ext2fs_mark_block_bitmap2(new_map, EXT2FS_B2C(rfs->new_fs, d));
+	}
+
+	/* Find changes in block allocations for bg metadata */
+	for (b = 0; b < ext2fs_blocks_count(rfs->new_fs->super); b++) {
+		c = EXT2FS_B2C(rfs->new_fs, b);
+		old = ext2fs_test_block_bitmap2(old_map, c);
+		new = ext2fs_test_block_bitmap2(new_map, c);
+
+		if (old && !new)
+			ext2fs_unmark_block_bitmap2(rfs->new_fs->block_map, c);
+		else if (!old && new)
+			; /* empty ext2fs_mark_block_bitmap2(new_map, c); */
+		else
+			ext2fs_unmark_block_bitmap2(new_map, c);
+	}
+	/* new_map now shows blocks that have been newly allocated. */
+
+	/* Move any conflicting bitmaps and inode tables */
+	for (i = 0; i < rfs->old_fs->group_desc_count; i++) {
+		b = EXT2FS_B2C(rfs->new_fs,
+			       ext2fs_block_bitmap_loc(rfs->new_fs, i));
+		if (ext2fs_test_block_bitmap2(new_map, b))
+			ext2fs_block_bitmap_loc_set(rfs->new_fs, i, 0);
+
+		b = EXT2FS_B2C(rfs->new_fs,
+			       ext2fs_inode_bitmap_loc(rfs->new_fs, i));
+		if (ext2fs_test_block_bitmap2(new_map, b))
+			ext2fs_inode_bitmap_loc_set(rfs->new_fs, i, 0);
+
+		c = ext2fs_inode_table_loc(rfs->new_fs, i);
+		for (b = 0; b < rfs->new_fs->inode_blocks_per_group; b++) {
+			if (ext2fs_test_block_bitmap2(new_map, b + c)) {
+				ext2fs_inode_table_loc_set(rfs->new_fs, i, 0);
+				break;
+			}
+		}
+	}
+
+out:
+	if (old_map)
+		ext2fs_free_block_bitmap(old_map);
+	if (new_map)
+		ext2fs_free_block_bitmap(new_map);
+	return retval;
+}
+
+/* Zero out the high bits of extent fields */
+static errcode_t zero_high_bits_in_extents(ext2_filsys fs, ext2_ino_t ino,
+				 struct ext2_inode *inode)
+{
+	ext2_extent_handle_t	handle;
+	struct ext2fs_extent	extent;
+	int			op = EXT2_EXTENT_ROOT;
+	errcode_t		errcode;
+
+	if (!(inode->i_flags & EXT4_EXTENTS_FL))
+		return 0;
+
+	errcode = ext2fs_extent_open(fs, ino, &handle);
+	if (errcode)
+		return errcode;
+
+	while (1) {
+		errcode = ext2fs_extent_get(handle, op, &extent);
+		if (errcode)
+			break;
+
+		op = EXT2_EXTENT_NEXT_SIB;
+
+		extent.e_pblk &= 0xFFFFFFFF;
+		errcode = ext2fs_extent_replace(handle, 0, &extent);
+		if (errcode)
+			break;
+	}
+
+	/* Ok if we run off the end */
+	if (errcode == EXT2_ET_EXTENT_NO_NEXT)
+		errcode = 0;
+	return errcode;
+}
+
+/* Zero out the high bits of inodes. */
+static errcode_t zero_high_bits_in_inodes(ext2_filsys fs)
+{
+	int length = EXT2_INODE_SIZE(fs->super);
+	struct ext2_inode *inode = NULL;
+	ext2_inode_scan	scan = NULL;
+	errcode_t	retval;
+	ext2_ino_t	ino;
+	blk64_t		file_acl_block;
+	__u32		sz_mask_high;
+	int		inode_dirty;
+
+	if (fs->super->s_creator_os != EXT2_OS_LINUX)
+		return 0;
+
+	retval = ext2fs_open_inode_scan(fs, 0, &scan);
+	if (retval)
+		return retval;
+
+	retval = ext2fs_get_mem(length, &inode);
+	if (retval)
+		goto out;
+
+	sz_mask_high = (((1ULL << 32) * EXT2_BLOCK_SIZE(fs->super)) - 1) >> 32;
+	do {
+		retval = ext2fs_get_next_inode_full(scan, &ino, inode, length);
+		if (retval)
+			goto out;
+		if (!ino)
+			break;
+		if (!ext2fs_test_inode_bitmap2(fs->inode_map, ino))
+			continue;
+
+		inode->i_size_high &= sz_mask_high;
+		inode->osd2.linux2.l_i_blocks_hi = 0;
+		inode->osd2.linux2.l_i_file_acl_high = 0;
+
+		retval = ext2fs_write_inode_full(fs, ino, inode,
+						 length);
+		if (retval)
+			goto out;
+
+		retval = zero_high_bits_in_extents(fs, ino, inode);
+		if (retval)
+			goto out;
+	} while (ino);
+
+out:
+	if (inode)
+		ext2fs_free_mem(&inode);
+	if (scan)
+		ext2fs_close_inode_scan(scan);
+}
+
 /*
  * Clean up the bitmaps for unitialized bitmaps
  */
@@ -424,7 +679,8 @@  retry:
 	/*
 	 * Reallocate the group descriptors as necessary.
 	 */
-	if (old_fs->desc_blocks != fs->desc_blocks) {
+	if (EXT2_DESC_SIZE(old_fs->super) == EXT2_DESC_SIZE(fs->super) &&
+	    old_fs->desc_blocks != fs->desc_blocks) {
 		retval = ext2fs_resize_mem(old_fs->desc_blocks *
 					   fs->blocksize,
 					   fs->desc_blocks * fs->blocksize,
@@ -939,7 +1195,9 @@  static errcode_t blocks_to_move(ext2_resize_t rfs)
 		new_blocks = fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
 	}
 
-	if (old_blocks == new_blocks) {
+	if (EXT2_DESC_SIZE(rfs->old_fs->super) ==
+	    EXT2_DESC_SIZE(rfs->new_fs->super) &&
+	    old_blocks == new_blocks) {
 		retval = 0;
 		goto errout;
 	}
diff --git a/resize/resize2fs.h b/resize/resize2fs.h
index d425491..e24319d 100644
--- a/resize/resize2fs.h
+++ b/resize/resize2fs.h
@@ -81,6 +81,9 @@  typedef struct ext2_sim_progress *ext2_sim_progmeter;
 #define RESIZE_PERCENT_COMPLETE		0x0100
 #define RESIZE_VERBOSE			0x0200
 
+#define RESIZE_ENABLE_64BIT		0x0400
+#define RESIZE_DISABLE_64BIT		0x0800
+
 /*
  * This structure is used for keeping track of how much resources have
  * been used for a particular resize2fs pass.