kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq
authorTejun Heo <tj@kernel.org>
Mon, 3 Feb 2014 19:02:55 +0000 (14:02 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 7 Feb 2014 23:42:40 +0000 (15:42 -0800)
commitabd54f028ec30976d6e797e7474ec91d96186a0c
tree3fc9f5240ec0dfdcb210499878e08a18a678157f
parenta6607930b6cd829fc7f680b48a937d827e0bb931
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.

v2: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
    KERNFS_LOCKDEP flag").

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