kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq
authorTejun Heo <tj@kernel.org>
Fri, 10 Jan 2014 13:57:19 +0000 (08:57 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 10 Jan 2014 21:44:25 +0000 (13:44 -0800)
commitea1c472dfeada211a0100daa7976e8e8e779b858
treeba19d47bf769857075edccba0f6006004ec6bb91
parentd92d2e6bd72b653f9811e0c9c46307c743b3fc58
kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq

kernfs_node->u.completion is used to notify deactivation completion
from kernfs_put_active() to kernfs_deactivate().  We now allow
multiple racing removals of the same node and the current removal
scheme is no longer correct - kernfs_remove() invocation may return
before the node is properly deactivated if it races against another
removal.  The removal path will be restructured to address the issue.

To help such restructure which requires supporting multiple waiters,
this patch replaces kernfs_node->u.completion with
kernfs_root->deactivate_waitq.  This makes deactivation event
notifications share a per-root waitqueue_head; however, the wait path
is quite cold and this will also allow shaving one pointer off
kernfs_node.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/kernfs/dir.c
include/linux/kernfs.h