tree 1ba64923f2800b949e1ebe7b5f591a8ccb5456fa
parent 356b5e16be485aac5a8c07d8f8bef88c52aaee68
author Al Viro <viro@ZenIV.linux.org.uk> 1496470809 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1553663584 +0900

Hang/soft lockup in d_invalidate with simultaneous calls

commit 81be24d263dbeddaba35827036d6f6787a59c2c3 upstream.

It's not hard to trigger a bunch of d_invalidate() on the same
dentry in parallel.  They end up fighting each other - any
dentry picked for removal by one will be skipped by the rest
and we'll go for the next iteration through the entire
subtree, even if everything is being skipped.  Morevoer, we
immediately go back to scanning the subtree.  The only thing
we really need is to dissolve all mounts in the subtree and
as soon as we've nothing left to do, we can just unhash the
dentry and bugger off.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>