workqueue: make alloc_workqueue() take printf fmt and args for name

alloc_workqueue() currently expects the passed in @name pointer to remain
accessible.  This is inconvenient and a bit silly given that the whole wq
is being dynamically allocated.  This patch updates alloc_workqueue() and
friends to take printf format string instead of opaque string and matching
varargs at the end.  The name is allocated together with the wq and
formatted.

alloc_ordered_workqueue() is converted to a macro to unify varargs
handling with alloc_workqueue(), and, while at it, add comment to
alloc_workqueue().

None of the current in-kernel users pass in string with '%' as constant
name and this change shouldn't cause any problem.

[akpm@linux-foundation.org: use __printf]
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 10 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 42fa9ad0a810..bec7b5b53e03 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -242,10 +242,10 @@ struct workqueue_struct {
 
         int                     nr_drainers;    /* W: drain in progress */
         int                     saved_max_active; /* W: saved cwq max_active */
-        const char              *name;          /* I: workqueue name */
 #ifdef CONFIG_LOCKDEP
         struct lockdep_map      lockdep_map;
 #endif
+        char                    name[];         /* I: workqueue name */
 };
 
 struct workqueue_struct *system_wq __read_mostly;
@@ -2954,14 +2954,29 @@ static int wq_clamp_max_active(int max_active, unsigned int flags,
         return clamp_val(max_active, 1, lim);
 }
 
-struct workqueue_struct *__alloc_workqueue_key(const char *name,
+struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
                                                unsigned int flags,
                                                int max_active,
                                                struct lock_class_key *key,
-                                               const char *lock_name)
+                                               const char *lock_name, ...)
 {
+        va_list args, args1;
         struct workqueue_struct *wq;
         unsigned int cpu;
+        size_t namelen;
+
+        /* determine namelen, allocate wq and format name */
+        va_start(args, lock_name);
+        va_copy(args1, args);
+        namelen = vsnprintf(NULL, 0, fmt, args) + 1;
+
+        wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL);
+        if (!wq)
+                goto err;
+
+        vsnprintf(wq->name, namelen, fmt, args1);
+        va_end(args);
+        va_end(args1);
 
         /*
          * Workqueues which may be used during memory reclaim should
@@ -2978,12 +2993,9 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
                 flags |= WQ_HIGHPRI;
 
         max_active = max_active ?: WQ_DFL_ACTIVE;
-        max_active = wq_clamp_max_active(max_active, flags, name);
-
-        wq = kzalloc(sizeof(*wq), GFP_KERNEL);
-        if (!wq)
-                goto err;
+        max_active = wq_clamp_max_active(max_active, flags, wq->name);
 
+        /* init wq */
         wq->flags = flags;
         wq->saved_max_active = max_active;
         mutex_init(&wq->flush_mutex);
@@ -2991,7 +3003,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
         INIT_LIST_HEAD(&wq->flusher_queue);
         INIT_LIST_HEAD(&wq->flusher_overflow);
 
-        wq->name = name;
         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
         INIT_LIST_HEAD(&wq->list);
 
@@ -3020,7 +3031,8 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
                 if (!rescuer)
                         goto err;
 
-                rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
+                rescuer->task = kthread_create(rescuer_thread, wq, "%s",
+                                               wq->name);
                 if (IS_ERR(rescuer->task))
                         goto err;