Re: flushing HFS cache to disk
Re: flushing HFS cache to disk
- Subject: Re: flushing HFS cache to disk
- From: Don Brady <email@hidden>
- Date: Tue, 29 Nov 2005 14:06:42 -0700
On Nov 29, 2005, at 12:33 PM, email@hidden wrote:
At 9:39 Uhr -0800 29.11.2005, Shantonu Sen wrote:
that's what sync(2) does.
It doesn't seem to.
What information in particular do you not think is getting flushed
to disk.
E.g. when I delete a file this change is not written to the HFS
catalog tree after calling sync() - the tree still contains this
entry.
And why in the world are you accessing the filesystem through the
raw device instead of the mounted filesystem. Even if you sync(2),
you're never going to get a coherent snapshot of the filesystem
that is mounted read/write.
I need to get a list of all files with related information. Reading
this list from the HFS catalog tree is much faster than looping and
stat-ing through all directories (e.g. with 500.000 entries:
seconds compared to minutes) - while both will not result in a
coherent snapshot.
If you just need to search the catalog why not use searchfs(2) or the
related Carbon call (PBCatSearch)?
-Don
Shantonu
On Nov 29, 2005, at 2:38 AM, email@hidden wrote:
In order to read _current_ HFS data from a mounted disk we need
to flush the HFS cache to disk before we start to read.
- Calling sync() does not do the job - data on disk is not
updated with HFS cache.
- Opening the disk with open("/dev/rdsk0s10", O_RDWR) or (open
("/", O_RDWR) and calling fsync(diskfd) or ioctl(diskfd,
DKIOCSYNCHRONIZECACHE) does not do it - data on disk is not
updated with HFS cache.
- Starting Disk Utility does the job - afterwards the HFS data on
disk is updated with current information.
Any idea how Disk Utility forces to flush the HFS cache to disk,
and how we can do it in our code (without having to start Disk
Utility ;-))?
Thanks,
Uwe Gohlke
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Uwe Gohlke
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