From patchwork Mon Apr 16 18:02:34 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [04/10] fsnotify: take groups mark_lock before mark lock From: Andy Whitcroft X-Patchwork-Id: 152957 Message-Id: <1334599360-15346-5-git-send-email-apw@canonical.com> To: kernel-team@lists.ubuntu.com Cc: Andy Whitcroft Date: Mon, 16 Apr 2012 19:02:34 +0100 From: Lino Sanfilippo Race-free addition and removal of a mark to a groups mark list would be easier if we could lock the mark list of group before we lock the specific mark. This patch changes the order used to add/remove marks to/from mark lists from 1. mark->lock 2. group->mark_lock 3. inode->i_lock to 1. group->mark_lock 2. mark->lock 3. inode->i_lock Signed-off-by: Lino Sanfilippo Signed-off-by: Eric Paris (cherry-picked from commit f1ae5e850a85e0db65d95c13ed6cc31d2450c5f2 git://git.infradead.org/users/eparis/notify.git) BugLink: http://bugs.launchpad.net/bugs/922906 Signed-off-by: Andy Whitcroft --- fs/notify/mark.c | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/fs/notify/mark.c b/fs/notify/mark.c index 5b784aa..3f6cdbd 100644 --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -128,20 +128,27 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) struct inode *inode = NULL; spin_lock(&mark->lock); - + /* dont get the group from a mark that is not alive yet */ + if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { + spin_unlock(&mark->lock); + return; + } fsnotify_get_group(mark->group); group = mark->group; + spin_unlock(&mark->lock); + + spin_lock(&group->mark_lock); + spin_lock(&mark->lock); /* something else already called this function on this mark */ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { spin_unlock(&mark->lock); + spin_unlock(&group->mark_lock); goto put_group; } mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; - spin_lock(&group->mark_lock); - if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) { inode = mark->i.inode; fsnotify_destroy_inode_mark(mark); @@ -152,8 +159,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) list_del_init(&mark->g_list); - spin_unlock(&group->mark_lock); spin_unlock(&mark->lock); + spin_unlock(&group->mark_lock); spin_lock(&destroy_lock); list_add(&mark->destroy_list, &destroy_list); @@ -227,13 +234,13 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, /* * LOCKING ORDER!!!! - * mark->lock * group->mark_lock + * mark->lock * inode->i_lock */ - spin_lock(&mark->lock); spin_lock(&group->mark_lock); + spin_lock(&mark->lock); mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE; fsnotify_get_group(group); @@ -254,13 +261,12 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, BUG(); } - spin_unlock(&group->mark_lock); - /* this will pin the object if appropriate */ fsnotify_set_mark_mask_locked(mark, mark->mask); - spin_unlock(&mark->lock); + spin_unlock(&group->mark_lock); + if (inode) __fsnotify_update_child_dentry_flags(inode); @@ -272,8 +278,8 @@ err: mark->group = NULL; atomic_dec(&group->num_marks); - spin_unlock(&group->mark_lock); spin_unlock(&mark->lock); + spin_unlock(&group->mark_lock); spin_lock(&destroy_lock); list_add(&mark->destroy_list, &destroy_list);