Re: [RFC] [PATCH] tapset to count number open file handlers and max file handlers for a process

[Srinivasa Ds <srinivasa at in dot ibm dot com>]

Frank Ch. Eigler wrote:

> 
> Thanks, but not quite: *every link* needs to be protected.  For
> example, this expression has three, so you'll need temporary variables
> or more nesting/casting:
> 
>> THIS->__retvalue = kread(&(t->files->fdt->max_fds));

Done

 
>>> Finally, for a real check-in, one would need documentation in stapfuncs
>>> and at least a buildok item in the test suite.
>> I am ready to work on this.
> 
> Great.

Iam attching tapset function and testcase(I have just extended the 
buildok/task_test.stp). I didn't find documentation for tapsets(present 
in tapset/task.stp) in src/man dir, Shall I write a new man page for 
all the functions in task.stp?

Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>


---
 tapset/task.stp                 |   31 +++++++++++++++++++++++++++++++
 testsuite/buildok/task_test.stp |    2 ++
 2 files changed, 33 insertions(+)

Index: src/tapset/task.stp
===================================================================
--- src.orig/tapset/task.stp
+++ src/tapset/task.stp
@@ -6,6 +6,10 @@
 // Public License (GPL); either version 2, or (at your option) any
 // later version.
 
+%{
+#include <linux/version.h>
+#include <linux/file.h>
+%}
 
 // Return the task_struct representing the current process
 function task_current:long () %{ /* pure */
@@ -125,3 +129,30 @@ function task_cpu:long (task:long)
     CATCH_DEREF_FAULT();
 %}
 %)
+
+
+// Return the number of open file handlers for the given task
+function task_open_file_handler:long (task:long) %{
+    struct task_struct *t = (struct task_struct *)(long)THIS->task;
+    struct fdtable *fdt = kread(&(t->files->fdt));
+    unsigned int count=0, fd;
+    rcu_read_lock();
+    for (fd = 0; fd < kread(&(fdt->max_fds)); fd++) {
+                if ( kread(&(fdt->fd[fd])) != NULL)
+                        count ++;
+        }
+    rcu_read_unlock();
+    THIS->__retvalue = count;
+    CATCH_DEREF_FAULT();
+%}
+
+
+// Return the maximum number of file handlers for the given task
+function task_max_file_handler:long (task:long) %{
+    struct task_struct *t = (struct task_struct *)(long)THIS->task;
+    struct files_struct *f = kread (&(t->files));
+    rcu_read_lock();
+    THIS->__retvalue = kread(&(f->fdt->max_fds));
+    rcu_read_unlock();
+    CATCH_DEREF_FAULT();
+%}
Index: src/testsuite/buildok/task_test.stp
===================================================================
--- src.orig/testsuite/buildok/task_test.stp
+++ src/testsuite/buildok/task_test.stp
@@ -14,5 +14,7 @@ probe begin {
   log(sprint(task_prio(c)))
   log(sprint(task_nice(c)))
   log(sprint(task_cpu(c)))
+  log(sprint(task_open_file_handler(c)))
+  log(sprint(task_max_file_handler(c)))
   exit()
 }