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Re: Vnode API change: add global vnode cache
Date: Mon, 7 Apr 2014 18:32:02 +0200
From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
On 07 Apr 2014, at 18:02, Taylor R Campbell
> In that case, could you set the VI_CHANGING bit in vp, rather than
> node->vn_vnode = NULL in the vcache node, to indicate that the vnode
> is being initialized in vcache_intern?
This will not work for layered file systems. They will share the
v_interlock from another vnode (in VFS_LOAD_NODE) so we better don't use
the interlock before loading the fs node.
You can pass the shared interlock to vcache_intern, like I illustrated
in the code I attached.
> Perhaps we ought at least to change VFS_VGET so it returns the vnode
> unlocked, and once we do that, use it consistently to look up vnodes
> by inode number rather than calling vcache_intern in multiple
> different places.
Maybe in the far future. Already looked at it and it is a very big job
if we want to do it in one step.
We could do this for just ufs:
1. Add ufs_vget_unlocked to make the sole call to vcache_intern for
2. Make ufs_vget call ufs_vget_unlocked and then lock the result.
3. Replace calls to VFS_VGET by ufs_vget_unlocked, rather than by
Then, when we fix VFS_VGET, we replace ufs_vget by ufs_vget_unlocked.
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