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fsnotify: clean up fsnotify_prepare/finish_user_wait()
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> Cc: <stable@vger.kernel.org> # v4.12 Signed-off-by: Jan Kara <jack@suse.cz>
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@ -109,16 +109,6 @@ void fsnotify_get_mark(struct fsnotify_mark *mark)
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atomic_inc(&mark->refcnt);
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}
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/*
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* Get mark reference when we found the mark via lockless traversal of object
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* list. Mark can be already removed from the list by now and on its way to be
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* destroyed once SRCU period ends.
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*/
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static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
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{
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return atomic_inc_not_zero(&mark->refcnt);
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}
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static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
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{
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u32 new_mask = 0;
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@ -256,32 +246,63 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
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FSNOTIFY_REAPER_DELAY);
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}
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bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
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/*
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* Get mark reference when we found the mark via lockless traversal of object
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* list. Mark can be already removed from the list by now and on its way to be
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* destroyed once SRCU period ends.
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*
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* Also pin the group so it doesn't disappear under us.
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*/
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static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
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{
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struct fsnotify_group *group;
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if (WARN_ON_ONCE(!iter_info->inode_mark && !iter_info->vfsmount_mark))
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return false;
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if (iter_info->inode_mark)
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group = iter_info->inode_mark->group;
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else
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group = iter_info->vfsmount_mark->group;
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if (!mark)
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return true;
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group = mark->group;
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/*
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* Since acquisition of mark reference is an atomic op as well, we can
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* be sure this inc is seen before any effect of refcount increment.
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*/
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atomic_inc(&group->user_waits);
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if (atomic_inc_not_zero(&mark->refcnt))
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return true;
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if (iter_info->inode_mark) {
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/* This can fail if mark is being removed */
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if (!fsnotify_get_mark_safe(iter_info->inode_mark))
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goto out_wait;
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if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
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wake_up(&group->notification_waitq);
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return false;
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}
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/*
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* Puts marks and wakes up group destruction if necessary.
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*
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* Pairs with fsnotify_get_mark_safe()
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*/
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static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
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{
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if (mark) {
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struct fsnotify_group *group = mark->group;
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fsnotify_put_mark(mark);
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/*
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* We abuse notification_waitq on group shutdown for waiting for
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* all marks pinned when waiting for userspace.
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*/
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if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
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wake_up(&group->notification_waitq);
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}
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if (iter_info->vfsmount_mark) {
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if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark))
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goto out_inode;
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}
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bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
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{
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/* This can fail if mark is being removed */
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if (!fsnotify_get_mark_safe(iter_info->inode_mark))
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return false;
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if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark)) {
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fsnotify_put_mark_wake(iter_info->inode_mark);
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return false;
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}
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/*
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@ -292,34 +313,13 @@ bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
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srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
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return true;
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out_inode:
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if (iter_info->inode_mark)
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fsnotify_put_mark(iter_info->inode_mark);
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out_wait:
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if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
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wake_up(&group->notification_waitq);
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return false;
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}
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void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
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{
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struct fsnotify_group *group = NULL;
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iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
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if (iter_info->inode_mark) {
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group = iter_info->inode_mark->group;
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fsnotify_put_mark(iter_info->inode_mark);
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}
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if (iter_info->vfsmount_mark) {
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group = iter_info->vfsmount_mark->group;
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fsnotify_put_mark(iter_info->vfsmount_mark);
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}
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/*
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* We abuse notification_waitq on group shutdown for waiting for all
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* marks pinned when waiting for userspace.
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*/
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if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
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wake_up(&group->notification_waitq);
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fsnotify_put_mark_wake(iter_info->inode_mark);
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fsnotify_put_mark_wake(iter_info->vfsmount_mark);
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}
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/*
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