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Date: Thu, 3 Jan 2008 15:03:06 -0500
From: Josef Bacik <jbacik@...hat.com>
To: Theodore Tso <tytso@....edu>
Cc: Josef Bacik <jbacik@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2fsprogs: add minimal resize size option
On Thu, Jan 03, 2008 at 12:21:01PM -0500, Theodore Tso wrote:
> On Wed, Jan 02, 2008 at 03:16:59PM -0500, Josef Bacik wrote:
> > Hello,
> >
> > People wishing to make live usb disks and such are looking for a way
> > to get the minimum resize size for an ext fs in blocks so that they
> > can just resize their image to that size and do with it what they
> > will. This patch adds that functionality, just pass -m option and
> > it calculates the minimum number of blocks the fs can be resized to.
>
> Three comments. Instead of using a new option, why not simply let
> resize2fs check to see if the optional parameter is something like
> "min" or "0"?
>
> Secondly, I'd suggest factoring out the calculation of the minimal
> size into a separate function.
>
> Finally, please don't fix whitespace issues, as it makes it harder for me
> to merge between the "maint" and "master" development lines. What I
> plan to do is to do a massive fixup of trailing whitespace before the
> next major (1.41) release of e2fsprogs. Any new lines added by
> patches should not introduce any new trailing whitespace, of course.
>
Hmm sorry about the whitespace things, I thought I had cleaned all those up.
Thanks much for the suggestions, here is the updated patch with your suggestions
implemented, if you pass a size of 0 it will just spit out the minimum resize
size. Thanks much,
Josef
diff --git a/resize/main.c b/resize/main.c
index 7c1d0c1..44d05b0 100644
--- a/resize/main.c
+++ b/resize/main.c
@@ -342,11 +342,8 @@ int main (int argc, char ** argv)
if (new_size_str) {
new_size = parse_num_blocks(new_size_str,
fs->super->s_log_block_size);
- if (!new_size) {
- com_err(program_name, 0, _("bad filesystem size - %s"),
- new_size_str);
- exit(1);
- }
+ if (!new_size)
+ flags |= RESIZE_BLOCKS_NEEDED_ONLY;
} else {
new_size = max_size;
/* Round down to an even multiple of a pagesize */
@@ -392,7 +389,8 @@ int main (int argc, char ** argv)
"long. Nothing to do!\n\n"), new_size);
exit(0);
}
- if (mount_flags & EXT2_MF_MOUNTED) {
+ if ((mount_flags & EXT2_MF_MOUNTED) &&
+ !(flags & RESIZE_BLOCKS_NEEDED_ONLY)) {
retval = online_resize_fs(fs, mtpt, &new_size, flags);
} else {
if (!force && ((fs->super->s_lastcheck < fs->super->s_mtime) ||
@@ -403,8 +401,10 @@ int main (int argc, char ** argv)
device_name);
exit(1);
}
- printf("Resizing the filesystem on %s to %u (%dk) blocks.\n",
- device_name, new_size, fs->blocksize / 1024);
+ if (!(flags & RESIZE_BLOCKS_NEEDED_ONLY))
+ printf("Resizing the filesystem on %s to %u (%dk) "
+ "blocks.\n", device_name, new_size,
+ fs->blocksize / 1024);
retval = resize_fs(fs, &new_size, flags,
((flags & RESIZE_PERCENT_COMPLETE) ?
resize_progress_func : 0));
@@ -415,11 +415,13 @@ int main (int argc, char ** argv)
ext2fs_close (fs);
exit(1);
}
- printf(_("The filesystem on %s is now %u blocks long.\n\n"),
- device_name, new_size);
- if ((st_buf.st_size > new_file_size) &&
- (fd > 0)) {
+ if (!(flags & RESIZE_BLOCKS_NEEDED_ONLY))
+ printf(_("The filesystem on %s is now %u blocks long.\n\n"),
+ device_name, new_size);
+
+ if ((st_buf.st_size > new_file_size) && (fd > 0) &&
+ !(flags & RESIZE_BLOCKS_NEEDED_ONLY)) {
#ifdef HAVE_FSTAT64
ftruncate64(fd, new_file_size);
#else
diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 9959671..ad50c30 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -48,7 +48,7 @@ static errcode_t inode_ref_fix(ext2_resize_t rfs);
static errcode_t move_itables(ext2_resize_t rfs);
static errcode_t fix_resize_inode(ext2_filsys fs);
static errcode_t ext2fs_calculate_summary_stats(ext2_filsys fs);
-
+static errcode_t ext2fs_calculate_minimum_resize_size(ext2_filsys fs);
/*
* Some helper CPP macros
*/
@@ -63,7 +63,9 @@ static errcode_t ext2fs_calculate_summary_stats(ext2_filsys fs);
((blk) < (FS_INODE_TB((fs), (i)) + \
(fs)->inode_blocks_per_group)))
-
+#define META_OVERHEAD(fs) (2 + (fs)->inode_blocks_per_group)
+#define SUPER_OVERHEAD(fs) (1 + (fs)->desc_blocks +\
+ (fs)->super->s_reserved_gdt_blocks)
/*
* This is the top-level routine which does the dirty deed....
@@ -80,6 +82,9 @@ errcode_t resize_fs(ext2_filsys fs, blk_t *new_size, int flags,
if (retval)
return retval;
+ if (flags & RESIZE_BLOCKS_NEEDED_ONLY)
+ return ext2fs_calculate_minimum_resize_size(fs);
+
/*
* Create the data structure
*/
@@ -1628,3 +1633,141 @@ static errcode_t ext2fs_calculate_summary_stats(ext2_filsys fs)
ext2fs_mark_super_dirty(fs);
return 0;
}
+
+/*
+ * calcluate the minimum number of blocks the given fs can be resized to
+ */
+static errcode_t ext2fs_calculate_minimum_resize_size(ext2_filsys fs)
+{
+ blk_t inode_count, blks_needed, groups, blk, data_blocks;
+ blk_t grp, data_needed, last_start;
+ int overhead = 0, old_group = -1, num_of_superblocks = 0;
+
+ /*
+ * first figure out how many group descriptors we need to
+ * handle the number of inodes we have
+ */
+ inode_count = fs->super->s_inodes_count -
+ fs->super->s_free_inodes_count;
+ blks_needed = ext2fs_div_ceil(inode_count,
+ fs->super->s_inodes_per_group) *
+ EXT2_BLOCKS_PER_GROUP(fs->super);
+ groups = ext2fs_div_ceil(blks_needed,
+ EXT2_BLOCKS_PER_GROUP(fs->super));
+
+ /*
+ * we need to figure out how many backup superblocks we have so we can
+ * account for that in the metadata
+ */
+ for (grp = 0; grp < fs->group_desc_count; grp++) {
+ if (ext2fs_bg_has_super(fs, grp))
+ num_of_superblocks++;
+ }
+
+ /* calculate how many blocks are needed for data */
+ data_needed = fs->super->s_blocks_count -
+ fs->super->s_free_blocks_count;
+ data_needed -= SUPER_OVERHEAD(fs) * num_of_superblocks;
+ data_needed -= META_OVERHEAD(fs) * fs->group_desc_count;
+
+ /*
+ * figure out how many data blocks we have given the number of groups
+ * we need for our inodes
+ */
+ data_blocks = groups * EXT2_BLOCKS_PER_GROUP(fs->super);
+ last_start = 0;
+ for (grp = 0; grp < groups; grp++) {
+ overhead = META_OVERHEAD(fs);
+
+ if (ext2fs_bg_has_super(fs, grp))
+ overhead += SUPER_OVERHEAD(fs);
+
+ /*
+ * we want to keep track of how much data we can store in
+ * the groups leading up to the last group so we can determine
+ * how big the last group needs to be
+ */
+ if (grp != (groups - 1))
+ last_start += EXT2_BLOCKS_PER_GROUP(fs->super) -
+ overhead;
+
+ data_blocks -= overhead;
+ }
+
+ /*
+ * if we need more group descriptors in order to accomodate our data
+ * then we need to add them here
+ */
+ while (data_needed > data_blocks) {
+ blk_t remainder = data_needed - data_blocks;
+ blk_t extra_grps;
+
+ /* figure out how many more groups we need for the data */
+ extra_grps = ext2fs_div_ceil(remainder,
+ EXT2_BLOCKS_PER_GROUP(fs->super));
+
+ data_blocks += extra_grps * EXT2_BLOCKS_PER_GROUP(fs->super);
+
+ /* ok we have to account for the last group */
+ overhead = META_OVERHEAD(fs);
+ if (ext2fs_bg_has_super(fs, groups-1))
+ overhead += SUPER_OVERHEAD(fs);
+ last_start += EXT2_BLOCKS_PER_GROUP(fs->super) - overhead;
+
+ for (grp = groups; grp < groups+extra_grps; grp++) {
+ overhead = META_OVERHEAD(fs);
+ if (ext2fs_bg_has_super(fs, grp))
+ overhead += SUPER_OVERHEAD(fs);
+
+ /*
+ * again, we need to see how much data we cram into
+ * all of the groups leading up to the last group
+ */
+ if (grp != (groups + extra_grps - 1))
+ last_start += EXT2_BLOCKS_PER_GROUP(fs->super)
+ - overhead;
+
+ data_blocks -= overhead;
+ }
+
+ groups += extra_grps;
+ }
+
+ /* now for the fun voodoo */
+ overhead = META_OVERHEAD(fs);
+
+ /*
+ * if this is the case then the last group is going to have data in it
+ * so we need to adjust the size of the last group accordingly
+ */
+ if (last_start < data_needed) {
+ blk_t remainder = data_needed - last_start;
+
+ /*
+ * 50 is a magic number that mkfs/resize uses to see if its
+ * even worth making/resizing the fs. basically you need to
+ * have at least 50 blocks in addition to the blocks needed
+ * for the metadata in the last group
+ */
+ if (remainder > 50)
+ overhead += remainder;
+ else
+ overhead += 50;
+ } else
+ overhead += 50;
+
+ if (ext2fs_bg_has_super(fs, groups-1))
+ overhead += SUPER_OVERHEAD(fs);
+
+ /*
+ * since our last group doesn't have to be BLOCKS_PER_GROUP large, we
+ * only do groups-1, and then add the number of blocks needed to
+ * handle the group descriptor metadata+data that we need
+ */
+ blks_needed = (groups-1) * EXT2_BLOCKS_PER_GROUP(fs->super);
+ blks_needed += overhead;
+
+ printf("Minimum resize size in blocks is %d\n", blks_needed);
+
+ return 0;
+}
diff --git a/resize/resize2fs.h b/resize/resize2fs.h
index f87d04e..14a2c3f 100644
--- a/resize/resize2fs.h
+++ b/resize/resize2fs.h
@@ -79,6 +79,7 @@ typedef struct ext2_sim_progress *ext2_sim_progmeter;
#define RESIZE_PERCENT_COMPLETE 0x0100
#define RESIZE_VERBOSE 0x0200
+#define RESIZE_BLOCKS_NEEDED_ONLY 0x0400
/*
* The core state structure for the ext2 resizer
-
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