NAK. There's now no way for code outside aio.c to use the reference counting
on iocbs, which is needed in other code.
-ben
On Wed, Nov 09, 2005 at 01:15:16PM -0800, Zach Brown wrote:
> aio: make ctx ref debugging depend on DEBUG
>
> Formalize ctx refcount debugging by putting it in legible inline functions and
> making it conditional on DEBUG. In doing so a bug is also fixed where the
> decref debugging was testing the ref count after dropping its reference,
> opening a race with another thread that might free.
>
> Signed-off-by: Zach Brown <[email protected]>
> ---
>
> fs/aio.c | 65 +++++++++++++++++++++++++++++-----------------------
> include/linux/aio.h | 4 ---
> 2 files changed, 37 insertions(+), 32 deletions(-)
>
> Index: 2.6.14-mm1-aio-cleanups/fs/aio.c
> ===================================================================
> --- 2.6.14-mm1-aio-cleanups.orig/fs/aio.c 2005-11-09 11:48:27.394115109 -0800
> +++ 2.6.14-mm1-aio-cleanups/fs/aio.c 2005-11-09 11:52:30.663874807 -0800
> @@ -37,8 +37,10 @@
>
> #if DEBUG > 1
> #define dprintk printk
> +#define AIO_DEBUG_BUG_ON BUG_ON
> #else
> #define dprintk(x...) do { ; } while (0)
> +#define AIO_DEBUG_BUG_ON(x...) do { ; } while (0)
> #endif
>
> /*------ sysctl variables----*/
> @@ -171,6 +173,40 @@
> return 0;
> }
>
> +static inline void get_ioctx(struct kioctx *ctx)
> +{
> + AIO_DEBUG_BUG_ON(atomic_read(&ctx->users) <= 0);
> + atomic_inc(&ctx->users);
> +}
> +
> +static void __put_ioctx(struct kioctx *ctx)
> +{
> + unsigned nr_events = ctx->max_reqs;
> +
> + BUG_ON(ctx->reqs_active);
> +
> + cancel_delayed_work(&ctx->wq);
> + flush_workqueue(aio_wq);
> + aio_free_ring(ctx);
> + mmdrop(ctx->mm);
> + ctx->mm = NULL;
> + pr_debug("__put_ioctx: freeing %p\n", ctx);
> + kmem_cache_free(kioctx_cachep, ctx);
> +
> + if (nr_events) {
> + spin_lock(&aio_nr_lock);
> + BUG_ON(aio_nr - nr_events > aio_nr);
> + aio_nr -= nr_events;
> + spin_unlock(&aio_nr_lock);
> + }
> +}
> +
> +static inline void put_ioctx(struct kioctx *ctx)
> +{
> + AIO_DEBUG_BUG_ON(atomic_read(&ctx->users) == 0);
> + if (atomic_dec_and_test(&ctx->users))
> + __put_ioctx(ctx);
> +}
>
> /* aio_ring_event: returns a pointer to the event at the given index from
> * kmap_atomic(, km). Release the pointer with put_aio_ring_event();
> @@ -255,7 +291,7 @@
> return ctx;
>
> out_cleanup:
> - __put_ioctx(ctx);
> + put_ioctx(ctx);
> return ERR_PTR(-EAGAIN);
>
> out_freectx:
> @@ -360,33 +396,6 @@
> }
> }
>
> -/* __put_ioctx
> - * Called when the last user of an aio context has gone away,
> - * and the struct needs to be freed.
> - */
> -void fastcall __put_ioctx(struct kioctx *ctx)
> -{
> - unsigned nr_events = ctx->max_reqs;
> -
> - if (unlikely(ctx->reqs_active))
> - BUG();
> -
> - cancel_delayed_work(&ctx->wq);
> - flush_workqueue(aio_wq);
> - aio_free_ring(ctx);
> - mmdrop(ctx->mm);
> - ctx->mm = NULL;
> - pr_debug("__put_ioctx: freeing %p\n", ctx);
> - kmem_cache_free(kioctx_cachep, ctx);
> -
> - if (nr_events) {
> - spin_lock(&aio_nr_lock);
> - BUG_ON(aio_nr - nr_events > aio_nr);
> - aio_nr -= nr_events;
> - spin_unlock(&aio_nr_lock);
> - }
> -}
> -
> /* aio_get_req
> * Allocate a slot for an aio request. Increments the users count
> * of the kioctx so that the kioctx stays around until all requests are
> Index: 2.6.14-mm1-aio-cleanups/include/linux/aio.h
> ===================================================================
> --- 2.6.14-mm1-aio-cleanups.orig/include/linux/aio.h 2005-11-09 11:48:22.848483645 -0800
> +++ 2.6.14-mm1-aio-cleanups/include/linux/aio.h 2005-11-09 11:48:31.907756204 -0800
> @@ -198,7 +198,6 @@
> extern int FASTCALL(aio_put_req(struct kiocb *iocb));
> extern void FASTCALL(kick_iocb(struct kiocb *iocb));
> extern int FASTCALL(aio_complete(struct kiocb *iocb, long res, long res2));
> -extern void FASTCALL(__put_ioctx(struct kioctx *ctx));
> struct mm_struct;
> extern void FASTCALL(exit_aio(struct mm_struct *mm));
> extern struct kioctx *lookup_ioctx(unsigned long ctx_id);
> @@ -210,9 +209,6 @@
> int FASTCALL(io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> struct iocb *iocb));
>
> -#define get_ioctx(kioctx) do { if (unlikely(atomic_read(&(kioctx)->users) <= 0)) BUG(); atomic_inc(&(kioctx)->users); } while (0)
> -#define put_ioctx(kioctx) do { if (unlikely(atomic_dec_and_test(&(kioctx)->users))) __put_ioctx(kioctx); else if (unlikely(atomic_read(&(kioctx)->users) < 0)) BUG(); } while (0)
> -
> #define in_aio() !is_sync_wait(current->io_wait)
> /* may be used for debugging */
> #define warn_if_async() \
--
"Time is what keeps everything from happening all at once." -- John Wheeler
-
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