Re: problems with hfs_truncatefs() / HFS_RESIZE_VOLUME
Re: problems with hfs_truncatefs() / HFS_RESIZE_VOLUME
- Subject: Re: problems with hfs_truncatefs() / HFS_RESIZE_VOLUME
- From: Michael Alfred Schmidt <email@hidden>
- Date: Fri, 23 Jan 2009 09:25:17 +0100
Shantonu,
I'm testing on a MacBook Pro with default
factory partitioning, i.e. there are 128 MB left free on top of the OS
partition (see http://developer.apple.com/technotes/tn2006/tn2166.html#SECPARTITIONINGPOLICY).
I verify upfront with 'diskutil resizeVolume <resp.
volume device> limits' what
freedom to expand or shrink I have. Since my goal is to shrink the partition
rather than to expand it anyway, I concentrate my tests on shrinking (by
~ 10%).
Michael
| Shantonu Sen <email@hidden>
22.01.2009 18:11
|
|
To
| Michael Alfred Schmidt <email@hidden>
|
|
cc
| mm w <email@hidden>,
email@hidden
|
|
Subject
| Re: problems with hfs_truncatefs() /
HFS_RESIZE_VOLUME |
|
How do you know it has space to expand? You know you have
to repartition the disk first, right (so that the container block device
is large enough).
This fsctl is something that is straightforward to use
the same way the Disk Utility/diskutil use it. How big is your filesystem?
How many allocation blocks? What sizes are you requesting?
Shantonu Sen
email@hidden
Sent from my Mac Pro
On Jan 22, 2009, at 9:06 AM, Michael Alfred Schmidt wrote:
I do get ENOSPC
in case the code runs into 'hfs_extendfs(): not
enough space on device', or
EINVAL
in case the code runs into 'hfs_truncatefs(): invalid
size'. I get both erros with
my test program when I only try often enough, i. e. I get both errors for
the same value. The same behavior (both errors possible) applies to any
other arbitrary value of uiNewSize.
This is why I believe that the value is currently somehow lost.
The volume has both sufficient site to expand and to shrink.
Michael
you certainly get a ENOSPC message somewhere, bad sample you are using
- yoda
Cheers!
On Thu, Jan 22, 2009 at 8:16 AM, Michael Alfred Schmidt
<email@hidden>
wrote:
>
> Hi,
>
> I'm trying to shrink an HFS+ partition, just as 'diskutil resizeVolume...'
> does. However, I'm facing problems implementing the HFS_RESIZE_VOLUME
> command via fsctl(), as proposed by Amit Singh on p. 1572 of 'Mac
OS X
> Internals'.
>
> My code looks as follows:
>
> int iRet = 0;
>
> u_int32_t uiBlockSize;
> u_int64_t uiBlockCount, uiCurrentSize, uiNewSize;
>
> struct statfs StatFS;
>
> // only works if device mounted
> iRet = statfs ("/etc/", &StatFS);
> if (iRet < 0)
> {
> perror ("statfs failed with");
>
> return;
> }
>
> uiBlockSize = StatFS.f_bsize;
> uiBlockCount = StatFS.f_blocks;
>
>
> printf ("block size:\t %u\n", uiBlockSize);
> printf ("block count:\t %llu\n", uiBlockCount);
>
>
> uiCurrentSize = uiBlockSize * uiBlockCount;
> printf ("partition size:\t %llu\n\n", uiBlockSize * uiBlockCount);
>
> uiNewSize = uiCurrentSize; // only test here!!!
> printf ("new volume size: %llu, hex: %llX\n", uiNewSize,
uiNewSize);
>
>
> iRet = fsctl ("/", HFS_RESIZE_VOLUME, &uiNewSize, 0);
> if (iRet < 0)
> {
> perror ("fsctl failed with");
>
> return;
> }
>
>
> fsctl() fails with either 'hfs_extendfs(): not enough space on device'
or
> 'hfs_truncatefs(): invalid size', even if the new size equals the
old size
> (as in the code sample above). It looks like the &uiNewSize input
parameter
> is fully ignored, as other "new sizes" show the same unpredictable
results.
> On the kernel side, the respective code resides in bsd/hfs/hfs_readwrite.c.
> >From looking at that code, I cannot see any obvious mistake in
my code. I'm
> wondering whether there is any thunking (pointer conversion) problem
with
> the pointer to u_int64_t in the transition from userland to kernel.
>
> My target system is Mac OS X 10.5.x (Intel), compiled with XCode 3.1
with
> default build settings.
>
>
> I'm grateful for any idea on what's wrong with my code!
> Thanks in advance!
>
> Michael
>
>
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--
-mmw
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