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() \
-
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