[haiku-development] VFS and vnodes
- From: Julian Harnath <julian.harnath@xxxxxxxxxxxxxx>
- To: haiku-development <haiku-development@xxxxxxxxxxxxx>
- Date: Mon, 9 Jun 2014 12:00:03 +0200
Hello!
I'm currently working on a file-system add-on and have a few questions
regarding VNode usage in the VFS APIs.
There is fs_vnode_ops::read_dir(), where the FS add-on is supposed read
directory entries and fill them into dirent structs, which includes the
vnode ID.
Now, when an FS has file handles larger than sizeof(ino_t), it cannot
store sufficient information to find the node in the ID alone. So it
has to create a "fake" ID or hash of the handle and use that as vnode
ID... and to later find it again, insert a mapping from the ID to the
actual handle into some kind of global map. Or do I misunderstand
something?
The next question then is, how long do I have to retain the entry in
the global map? I can't retain it forever or the map would keep growing
without limits. For the case of fs_node_ops::lookup(), it's simpler
because I can remove it when put_vnode() is called. But for read_dir()
I can't even be sure that get_vnode() is ever called for an ID I assign
there, or can I?
--
So long, jua
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