[haiku-development] file modification watching
- From: Clemens <clemens.zeidler@xxxxxxxxxxxxxx>
- To: "haiku-development@xxxxxxxxxxxxx" <haiku-development@xxxxxxxxxxxxx>
- Date: Sat, 18 Jun 2011 08:51:17 +1200
Hi,
a few weeks ago when working on the music collection I noticed that the
current index server implementation is not really working and also not
optimal. The problem is that I need a notification in case a file has been
modified. Currently a modification query with intermediate updates is used
to do the job. The resolution of the modification time is just one second.
Though I get a mod notification but I have to wait one second to not miss
possible later changes (I don't wait at the moment).
For example, copying a music file to the disc usually takes less then a
second, when handling the first mod message the music file is almost empty
and the id3 tag analyser fails. the complete file is never analysed. This
problem does not appear when the file is already in the fs cache and thats
why I haven't noticed it before when testing it.
A simple solution would be to wait a second before start analysing but
then we still rely that the underlying fs supports queries. Monitoring
other volumes would not be possible. The other solution is to watch stat
changes. With a modification to the original be api, which is already in
the trunk, it is possible to watch changes of all nodes. This is fine
because at least bfs sends a stat changed notification when closing
(freeing the cookie) and time or size has changed. The problem is that a
node_ref is send out but in general I need a entry_ref to analyse a file.
There is no easy way to find a entry_ref (the path) to a node_ref.
Now my question to the experts. I thought about to add a table of open
nodes in the vfs. When opening a file in the vfs using file_open a node ->
path pair could be stored in a hash table. When file_close is called the
entry has to be removed again. When sending a stat or attr changed
notifications this information could be used to add an entry_ref to the
outgoing message. This could be done optional when the user adds an
additional flag in watch_node.
Is file_close also called when a team exit and the user forgot to close
files?
A further optimization would be to optional only send out notifications
when a file is closing.
Another not directly related question, why the fs and not the vfs is
responsible to send out notifications? At least for most notifications it
seams possible to me that the vfs has all needed information and can send
the message.
thank you,
Clemens
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