Re: [PATCH v3] fs/locks: print full locks information
From: Luo Longjun
Date: Wed Mar 10 2021 - 22:46:22 EST
在 2021/3/9 21:37, Jeff Layton 写道:
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@xxxxxxxxxx>
---
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.
In my understanding, the difference of "%*s" and "%.*s" is that, "%*s"
specifies the minimal filed width while "%.*s" specifies the precision
of the string.
Here, I use "%*s", because I want to print locks information in the
follwing format:
2: FLOCK ADVISORY WRITE 110 00:02:493 0 EOF
2: -> FLOCK ADVISORY WRITE 111 00:02:493 0 EOF
2: -> FLOCK ADVISORY WRITE 112 00:02:493 0 EOF
2: -> FLOCK ADVISORY WRITE 113 00:02:493 0 EOF
2: -> FLOCK ADVISORY WRITE 114 00:02:493 0 EOF
And also, there is another way to show there information, in the format
like:
60: FLOCK ADVISORY WRITE 23350 08:02:4456514 0 EOF
60: -> FLOCK ADVISORY WRITE 23356 08:02:4456514 0 EOF
60: -> FLOCK ADVISORY WRITE 24217 08:02:4456514 0 EOF
60: -> FLOCK ADVISORY WRITE 24239 08:02:4456514 0 EOF
I think both formats are acceptable, but the first format shows
competition relationships between these locks.
In the following code:
lock_get_status(f, fl, *id, "", 0);
repeat is 0, and in the function:
+ if (repeat)
+ seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx);
The if branch will not take effect, so it could not be -1.
+
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);
}
}