Dale Ghent wrote:
In my further study (ha!) of the Solaris client driver, I noticed that
the vfs unmount call unconditionally says "yo'kay" to umount requests
for /afs... which is alright if the /afs mount is quiescent and no
vnodes are referenced. But if there are, your machine is in panicville.
So I'm putting some safety in afs_unmount() and trying to figure out how
best to determine when returning EBUSY is appropriate.
Would I be correct in thinking that the most straight-forward approach
is to take the passed vfs struct that was passed in, get the vnode it
references, and see if v_count member is > 0 ?
I can only speak for the Solaris side of things.
As far as the Solaris VFS/VNODE framework is concerned you'd usually
check if the vnode's v_count is > 1 as the vnode is born
with a reference count of 1 (vn_alloc()->vn_reinit())
and return EBUSY in that case in your VFS_UNMOUNT() routine indicating
that you still have refrenced vnode's.
Note, you'd usually do this for any possible active vnode's in your
particular file system specific cache (e.g. the ufs inode cache)
Then there's the question of supporting forced unmounts... Are there any
good interfaces to call to invalidate all vcache/vnodes ?
if you want to implement forcible unmounts, there's kind of a
framework in the VFS/VNODE layer since Solaris 8 to do this. if you
decid to take that route, your busy check becomes much simpler
(against the vfs structures vfs->vfs_count) when using
VFS_HOLD()/VFS_RELE(). Let me know if you want to implement umount -f
for AFS and I'm happy to guide you to the interfaces and implementation
details, just drop me a note.
---
frankB
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