Re: [PATCH v2 02/24] fs/locks: print full locks information

[J. Bruce Fields]

On Wed, Feb 24, 2021 at 03:35:44AM -0500, Luo Longjun wrote:
> @@ -2912,17 +2922,66 @@ static int locks_show(struct seq_file *f, void *v)
>   struct file_lock *fl, *bfl;
>   struct pid_namespace *proc_pidns = 
> proc_pid_ns(file_inode(f->file)->i_sb);
>  
> + struct list_head root;
> + struct list_head *tail = 
> + struct list_head *pos, *tmp;
> + struct locks_traverse_list *node, *node_child;
> +
> + int ret = 0;
> +
>   fl = hlist_entry(v, struct file_lock, fl_link);
>  
>   if (locks_translate_pid(fl, proc_pidns) == 0)
> - return 0;
> + return ret;
> +
> + INIT_LIST_HEAD();
>  
> - lock_get_status(f, fl, iter->li_pos, "");
> + node = kmalloc(sizeof(struct locks_traverse_list), GFP_KERNEL);

Is it safe to allocate here?  I thought this was under the
blocked_lock_lock spinlock.

And I still don't think you need a stack.  Have you tried the suggestion
in my previous mail?

--b.

[PATCH v2 02/24] fs/locks: print full locks information

[Luo Longjun]

Commit fd7732e033e3 ("fs/locks: create a tree of dependent requests.")
has put blocked locks into a tree.

So, with a for loop, we can't check all locks information.

To solve this problem, we should traverse the tree by non-recursion DFS.

Signed-off-by: Luo Longjun 
---
 fs/locks.c | 75 --
 1 file changed, 67 insertions(+), 8 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 99ca97e81b7a..fdf240626777 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2827,8 +2827,14 @@ struct locks_iterator {
loff_t  li_pos;
 };
 
+struct locks_traverse_list {
+   struct list_head head;
+   struct file_lock *lock;
+   int level;
+};
+
 static void lock_get_status(struct seq_file *f, struct file_lock *fl,
-   loff_t id, char *pfx)
+   loff_t id, char *pfx, int repeat)
 {
struct inode *inode = NULL;
unsigned int fl_pid;
@@ -2844,7 +2850,11 @@ static void lock_get_status(struct seq_file *f, struct 
file_lock *fl,
if (fl->fl_file != NULL)
inode = locks_inode(fl->fl_file);
 
-   seq_printf(f, "%lld:%s ", id, pfx);
+   seq_printf(f, "%lld: ", id);
+
+   if (repeat)
+   seq_printf(f, "%*s", repeat - 1 + strlen(pfx), pfx);
+
if (IS_POSIX(fl)) {
if (fl->fl_flags & FL_ACCESS)
seq_puts(f, "ACCESS");
@@ -2912,17 +2922,66 @@ static int locks_show(struct seq_file *f, void *v)
struct file_lock *fl, *bfl;
struct pid_namespace *proc_pidns = 
proc_pid_ns(file_inode(f->file)->i_sb);
 
+   struct list_head root;
+   struct list_head *tail = 
+   struct list_head *pos, *tmp;
+   struct locks_traverse_list *node, *node_child;
+
+   int ret = 0;
+
fl = hlist_entry(v, struct file_lock, fl_link);
 
if (locks_translate_pid(fl, proc_pidns) == 0)
-   return 0;
+   return ret;
+
+   INIT_LIST_HEAD();
 
-   lock_get_status(f, fl, iter->li_pos, "");
+   node = kmalloc(sizeof(struct locks_traverse_list), GFP_KERNEL);
+   if (!node) {
+   ret = -ENOMEM;
+   goto out;
+   }
 
-   list_for_each_entry(bfl, >fl_blocked_requests, fl_blocked_member)
-   lock_get_status(f, bfl, iter->li_pos, " ->");
+   node->level = 0;
+   node->lock = fl;
+   list_add(>head, tail);
+   tail = >head;
 
-   return 0;
+   while (tail != ) {
+   node = list_entry(tail, struct locks_traverse_list, head);
+   if (!node->level)
+   lock_get_status(f, node->lock, iter->li_pos, "", 
node->level);
+   else
+   lock_get_status(f, node->lock, iter->li_pos, "-> ", 
node->level);
+
+   tmp = tail->prev;
+   list_del(tail);
+   tail = tmp;
+
+   list_for_each_entry_reverse(bfl, 
>lock->fl_blocked_requests,
+   fl_blocked_member) {
+   node_child = kmalloc(sizeof(struct 
locks_traverse_list), GFP_KERNEL);
+   if (!node_child) {
+   ret = -ENOMEM;
+   goto out;
+   }
+
+   node_child->level = node->level + 1;
+   node_child->lock = bfl;
+   list_add(_child->head, tail);
+   tail = _child->head;
+   }
+   kfree(node);
+   }
+
+out:
+   list_for_each_safe(pos, tmp, ) {
+   node = list_entry(pos, struct locks_traverse_list, head);
+   list_del(pos);
+   if (!node)
+   kfree(node);
+   }
+   return ret;
 }
 
 static void __show_fd_locks(struct seq_file *f,
@@ -2941,7 +3000,7 @@ static void __show_fd_locks(struct seq_file *f,
 
(*id)++;
seq_puts(f, "lock:\t");
-   lock_get_status(f, fl, *id, "");
+   lock_get_status(f, fl, *id, "", 0);
}
 }
 
-- 
2.17.1