Re: flushing HFS cache to disk
Re: flushing HFS cache to disk
- Subject: Re: flushing HFS cache to disk
- From: "Timothy J. Wood" <email@hidden>
- Date: Wed, 30 Nov 2005 14:35:23 -0800
On Nov 30, 2005, at 1:53 PM, Peter Bierman wrote:
But all the filesystem operations _do_ have transactional semantics.
The issue here is that someone is trying to read from the disk
_behind the back_ of the filesystem. There is NO provision for that
while the filesystem is in use.
They have transactional semantics in that each individual
operation is atomic, but they don't in that you can't group fs
operations into a transaction. Imagine some new syscalls:
fs_begin_transaction(xxx);
{
... do stuff ...
}
fs_{commit,rollback}_transaction();
In this particular case, you'd like 'xxx' to specify "don't show
me writes made by other processes", but a mode where you can prevent
your changes from becoming visible until you commit would be very
useful too (say, if you want to create two files and have them show
up atomically).
Obviously there are a whole ton of design issues with doing this,
problems this couldn't solve, and filesystems where this couldn't be
implemented easily (if at all).
-tim
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