commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647
author Al Viro <viro@zeniv.linux.org.uk> Fri Apr 24 15:47:07 2015 -0400
committer Al Viro <viro@zeniv.linux.org.uk> Fri Apr 24 15:52:14 2015 -0400
tree c696367810e2e603c3156127b6fb0eb4627a7132
parent ac74d8d65c83d8061034d0908e1eab6a0c24f923

RCU pathwalk breakage when running into a symlink overmounting something

Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something.  And in such cases we end up
with excessive mntput().

Cc: stable@vger.kernel.org # since 2.6.39
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>