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 EOFAnd 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 EOFI 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); } }
