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SubjectRe: [PATCH v3] fs/locks: print full locks information
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On Thu, 2021-02-25 at 22:58 -0500, Luo Longjun wrote:
> 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.
>
> Signed-off-by: Luo Longjun <luolongjun@huawei.com>
> ---
>  fs/locks.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 56 insertions(+), 9 deletions(-)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 99ca97e81b7a..ecaecd1f1b58 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2828,7 +2828,7 @@ struct locks_iterator {
>  };
>  
>
>
>
>  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 +2844,11 @@ 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 + (int)strlen(pfx), pfx);

Shouldn't that be "%.*s" ?

Also, isn't this likely to end up walking past the end of "pfx" (or even
ending up at an address before the buffer)? You have this below:

lock_get_status(f, fl, *id, "", 0);

...so the "length" value you're passing into the format there is going
to be -1. It also seems like if you get a large "level" value in
locks_show, then you'll end up with a length that is much longer than
the actual string.

> +
>   if (IS_POSIX(fl)) {
>   if (fl->fl_flags & FL_ACCESS)
>   seq_puts(f, "ACCESS");
> @@ -2906,21 +2910,64 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
>   }
>  }
>  
>
>
>
> +static struct file_lock *get_next_blocked_member(struct file_lock *node)
> +{
> + struct file_lock *tmp;
> +
> + /* NULL node or root node */
> + if (node == NULL || node->fl_blocker == NULL)
> + return NULL;
> +
> + /* Next member in the linked list could be itself */
> + tmp = list_next_entry(node, fl_blocked_member);
> + if (list_entry_is_head(tmp, &node->fl_blocker->fl_blocked_requests, fl_blocked_member)
> + || tmp == node) {
> + return NULL;
> + }
> +
> + return tmp;
> +}
> +
>  static int locks_show(struct seq_file *f, void *v)
>  {
>   struct locks_iterator *iter = f->private;
> - struct file_lock *fl, *bfl;
> + struct file_lock *cur, *tmp;
>   struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
> + int level = 0;
>  
>
>
>
> - fl = hlist_entry(v, struct file_lock, fl_link);
> + cur = hlist_entry(v, struct file_lock, fl_link);
>  
>
>
>
> - if (locks_translate_pid(fl, proc_pidns) == 0)
> + if (locks_translate_pid(cur, proc_pidns) == 0)
>   return 0;
>  
>
>
>
> - lock_get_status(f, fl, iter->li_pos, "");
> + /* View this crossed linked list as a binary tree, the first member of fl_blocked_requests
> + * is the left child of current node, the next silibing in fl_blocked_member is the
> + * right child, we can alse get the parent of current node from fl_blocker, so this
> + * question becomes traversal of a binary tree
> + */
> + while (cur != NULL) {
> + if (level)
> + lock_get_status(f, cur, iter->li_pos, "-> ", level);
> + else
> + lock_get_status(f, cur, iter->li_pos, "", level);
>  
>
>
>
> - list_for_each_entry(bfl, &fl->fl_blocked_requests, fl_blocked_member)
> - lock_get_status(f, bfl, iter->li_pos, " ->");
> + if (!list_empty(&cur->fl_blocked_requests)) {
> + /* Turn left */
> + cur = list_first_entry_or_null(&cur->fl_blocked_requests,
> + struct file_lock, fl_blocked_member);
> + level++;
> + } else {
> + /* Turn right */
> + tmp = get_next_blocked_member(cur);
> + /* Fall back to parent node */
> + while (tmp == NULL && cur->fl_blocker != NULL) {
> + cur = cur->fl_blocker;
> + level--;
> + tmp = get_next_blocked_member(cur);
> + }
> + cur = tmp;
> + }
> + }
>  
>
>
>
>   return 0;
>  }
> @@ -2941,7 +2988,7 @@ 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);
>   }
>  }
>  
>
>
>

--
Jeff Layton <jlayton@kernel.org>

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