Messages in this thread | | | Date | Fri, 26 Jul 2013 19:24:10 +0900 | From | Masami Hiramatsu <> | Subject | Re: Re: PATCH? debugfs_remove_recursive() must not rely on list_empty(d_subdirs) |
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(2013/07/26 5:04), Oleg Nesterov wrote: > On 07/25, Oleg Nesterov wrote: >> >> To simplify the review, this is how it looks with the patch applied: > > v2. We can use simply use list_for_each_entry_safe() and > list_next_entry() should be calles under ->i_mutex. Although > debugfs_remove_recursive() can race with itself anyway, but > still. > > And the code looks much simpler. But I do not know what did > I miss. > > Oleg. > > void debugfs_remove_recursive(struct dentry *dentry) > { > struct dentry *child, *next, *parent; > > if (IS_ERR_OR_NULL(dentry)) > return; > > parent = dentry->d_parent; > if (!parent || !parent->d_inode) > return; > > parent = dentry; > down: > mutex_lock(&parent->d_inode->i_mutex); > list_for_each_entry_safe(child, next, &parent->d_subdirs, d_u.d_child) {
Perhaps, you can use list_for_each_entry_safe_continue() here, as below.
parent = dentry; down: child = list_first_entry_or_null(&parent->d_subdirs, typeof(*child), d_u.d_child); mutex_lock(&parent->d_inode->i_mutex);
restart: list_for_each_entry_safe_continue(child, next, &parent->d_subdirs, d_u.d_child) {
> if (!debugfs_positive(child)) > continue; > > /* XXX: simple_empty(child) instead ? */ > if (!list_empty(&child->d_subdirs)) { > mutex_unlock(&parent->d_inode->i_mutex); > parent = child; > goto down; > } > up: > __debugfs_remove(child, parent); > }
Then, you can avoid jumping into the loop, just restart it from parent as below.
mutex_unlock(&parent->d_inode->i_mutex);
child = parent; parent = parent->d_parent; mutex_lock(&parent->d_inode->i_mutex); __debugfs_remove(child, parent);
if (child != dentry) goto restart;
> mutex_unlock(&parent->d_inode->i_mutex); > simple_release_fs(&debugfs_mount, &debugfs_mount_count); > }
It's just an idea, which came up to my mind. :)
Thank you,
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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