WorkStruct: Pass the work_struct pointer instead of context data

Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).


Signed-Off-By: David Howells <dhowells@redhat.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 11a1a7100ad6..ca1c5180a17f 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -53,13 +53,13 @@ static kmem_cache_t	*kioctx_cachep;
 static struct workqueue_struct *aio_wq;
 
 /* Used for rare fput completion. */
-static void aio_fput_routine(void *);
-static DECLARE_WORK(fput_work, aio_fput_routine, NULL);
+static void aio_fput_routine(struct work_struct *);
+static DECLARE_WORK(fput_work, aio_fput_routine);
 
 static DEFINE_SPINLOCK(fput_lock);
 static LIST_HEAD(fput_head);
 
-static void aio_kick_handler(void *);
+static void aio_kick_handler(struct work_struct *);
 static void aio_queue_work(struct kioctx *);
 
 /* aio_setup
@@ -227,7 +227,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 
         INIT_LIST_HEAD(&ctx->active_reqs);
         INIT_LIST_HEAD(&ctx->run_list);
-        INIT_DELAYED_WORK(&ctx->wq, aio_kick_handler, ctx);
+        INIT_DELAYED_WORK(&ctx->wq, aio_kick_handler);
 
         if (aio_setup_ring(ctx) < 0)
                 goto out_freectx;
@@ -470,7 +470,7 @@ static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
                 wake_up(&ctx->wait);
 }
 
-static void aio_fput_routine(void *data)
+static void aio_fput_routine(struct work_struct *data)
 {
         spin_lock_irq(&fput_lock);
         while (likely(!list_empty(&fput_head))) {
@@ -859,9 +859,9 @@ static inline void aio_run_all_iocbs(struct kioctx *ctx)
  *      space.
  * Run on aiod's context.
  */
-static void aio_kick_handler(void *data)
+static void aio_kick_handler(struct work_struct *work)
 {
-        struct kioctx *ctx = data;
+        struct kioctx *ctx = container_of(work, struct kioctx, wq.work);
         mm_segment_t oldfs = get_fs();
         int requeue;