4.14-stable review patch. If anyone has any objections, please let me know.
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From: Miklos Szeredi mszeredi@redhat.com
commit 24c20305c7fc8959836211cb8c50aab93ae0e54f upstream.
This patch doesn't actually fix any bug, just paves the way for fixing mark and group pinning.
Reviewed-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/notify/mark.c | 98 +++++++++++++++++++++++++++---------------------------- 1 file changed, 49 insertions(+), 49 deletions(-)
--- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -109,16 +109,6 @@ void fsnotify_get_mark(struct fsnotify_m atomic_inc(&mark->refcnt); }
-/* - * Get mark reference when we found the mark via lockless traversal of object - * list. Mark can be already removed from the list by now and on its way to be - * destroyed once SRCU period ends. - */ -static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark) -{ - return atomic_inc_not_zero(&mark->refcnt); -} - static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) { u32 new_mask = 0; @@ -256,32 +246,63 @@ void fsnotify_put_mark(struct fsnotify_m FSNOTIFY_REAPER_DELAY); }
-bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info) +/* + * Get mark reference when we found the mark via lockless traversal of object + * list. Mark can be already removed from the list by now and on its way to be + * destroyed once SRCU period ends. + * + * Also pin the group so it doesn't disappear under us. + */ +static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark) { struct fsnotify_group *group;
- if (WARN_ON_ONCE(!iter_info->inode_mark && !iter_info->vfsmount_mark)) - return false; - - if (iter_info->inode_mark) - group = iter_info->inode_mark->group; - else - group = iter_info->vfsmount_mark->group; + if (!mark) + return true;
+ group = mark->group; /* * Since acquisition of mark reference is an atomic op as well, we can * be sure this inc is seen before any effect of refcount increment. */ atomic_inc(&group->user_waits); + if (atomic_inc_not_zero(&mark->refcnt)) + return true; + + if (atomic_dec_and_test(&group->user_waits) && group->shutdown) + wake_up(&group->notification_waitq); + + return false; +} + +/* + * Puts marks and wakes up group destruction if necessary. + * + * Pairs with fsnotify_get_mark_safe() + */ +static void fsnotify_put_mark_wake(struct fsnotify_mark *mark) +{ + if (mark) { + struct fsnotify_group *group = mark->group;
- if (iter_info->inode_mark) { - /* This can fail if mark is being removed */ - if (!fsnotify_get_mark_safe(iter_info->inode_mark)) - goto out_wait; - } - if (iter_info->vfsmount_mark) { - if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark)) - goto out_inode; + fsnotify_put_mark(mark); + /* + * We abuse notification_waitq on group shutdown for waiting for + * all marks pinned when waiting for userspace. + */ + if (atomic_dec_and_test(&group->user_waits) && group->shutdown) + wake_up(&group->notification_waitq); + } +} + +bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info) +{ + /* This can fail if mark is being removed */ + if (!fsnotify_get_mark_safe(iter_info->inode_mark)) + return false; + if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark)) { + fsnotify_put_mark_wake(iter_info->inode_mark); + return false; }
/* @@ -292,34 +313,13 @@ bool fsnotify_prepare_user_wait(struct f srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
return true; -out_inode: - if (iter_info->inode_mark) - fsnotify_put_mark(iter_info->inode_mark); -out_wait: - if (atomic_dec_and_test(&group->user_waits) && group->shutdown) - wake_up(&group->notification_waitq); - return false; }
void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info) { - struct fsnotify_group *group = NULL; - iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); - if (iter_info->inode_mark) { - group = iter_info->inode_mark->group; - fsnotify_put_mark(iter_info->inode_mark); - } - if (iter_info->vfsmount_mark) { - group = iter_info->vfsmount_mark->group; - fsnotify_put_mark(iter_info->vfsmount_mark); - } - /* - * We abuse notification_waitq on group shutdown for waiting for all - * marks pinned when waiting for userspace. - */ - if (atomic_dec_and_test(&group->user_waits) && group->shutdown) - wake_up(&group->notification_waitq); + fsnotify_put_mark_wake(iter_info->inode_mark); + fsnotify_put_mark_wake(iter_info->vfsmount_mark); }
/*