Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3] fs/locks: print full locks information | From | Luo Longjun <> | Date | Thu, 11 Mar 2021 11:45:38 +0800 |
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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@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.
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); >> } >> } >> >> >> >>
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