[PATCH review 11/11] mnt: Honor MNT_LOCKED when detaching mounts

Al Viro viro at ZenIV.linux.org.uk
Thu Jan 8 03:11:24 UTC 2015

On Thu, Jan 08, 2015 at 03:02:29AM +0000, Al Viro wrote:
> BTW, why do you use detach_mnt() in __detach_mounts()?  Unless I'm missing
> something really subtle, __detach_mnt() is the right thing there...
> And while we are at it, all other callers of detach_mnt() are followed by
> attach_mnt() within the same namespace *and* all attach_mnt() follow
> detach_mnt().  So why bother with mnt_list in either?  Or, put it
> another way, why have __detach_mnt() separate from detach_mnt()?

I really don't like the look of __detach_mounts() after those changes.
Suppose we have a single "locked-and-lazy" vfsmount mounted on that
dentry.  With nothing mounted under it.  Your loop will do absolutely
nothing to it - it'll just keep spinning.

Why are you doing anything to the stuff mounted under than one, anyway?
It's this sucker you want to detach and kill...  Normal case (umount_tree())
will detach the vfsmount we are giving it; this one should have the same

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