From mboxrd@z Thu Jan 1 00:00:00 1970 From: J. Bruce Fields Date: Thu, 13 Jun 2013 15:45:46 -0400 Subject: [Cluster-devel] [PATCH v2 06/14] locks: don't walk inode->i_flock list in locks_show In-Reply-To: <1370948948-31784-7-git-send-email-jlayton@redhat.com> References: <1370948948-31784-1-git-send-email-jlayton@redhat.com> <1370948948-31784-7-git-send-email-jlayton@redhat.com> Message-ID: <20130613194545.GC19218@fieldses.org> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Tue, Jun 11, 2013 at 07:09:00AM -0400, Jeff Layton wrote: > When we convert over to using the i_lock to protect the i_flock list, > that will introduce a potential lock inversion problem in locks_show. > When we want to walk the i_flock list, we'll need to take the i_lock. > > Rather than do that, just walk the global blocked_locks list and print > out any that are blocked on the given lock. I'm OK with this as obviously /proc/locks shouldn't be the common case, but it still bugs me a bit that we're suddenly making it something like O(number of held locks * number of waiters) where it used to be O(number of held lock + number of waiters) I wonder if there's any solution that's just as easy and avoids scanning the blocked list each time. --b. > > Signed-off-by: Jeff Layton > --- > fs/locks.c | 6 ++++-- > 1 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/locks.c b/fs/locks.c > index e451d18..3fd27f0 100644 > --- a/fs/locks.c > +++ b/fs/locks.c > @@ -2249,8 +2249,10 @@ static int locks_show(struct seq_file *f, void *v) > > lock_get_status(f, fl, *((loff_t *)f->private), ""); > > - list_for_each_entry(bfl, &fl->fl_block, fl_block) > - lock_get_status(f, bfl, *((loff_t *)f->private), " ->"); > + list_for_each_entry(bfl, &blocked_list, fl_link) { > + if (bfl->fl_next == fl) > + lock_get_status(f, bfl, *((loff_t *)f->private), " ->"); > + } > > return 0; > } > -- > 1.7.1 >