aio: aio_nr decrements don't need to be delayed

we can do that right in __put_ioctx(); as the result, the loop
in ioctx_alloc() can be killed.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/aio.c b/fs/aio.c
index d09b56090aa5e7d1a2a9d60999b2a1048f539162..216eb37b2c7677633bbf2aead0b298eef51dccc3 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -199,16 +199,7 @@ static int aio_setup_ring(struct kioctx *ctx)
 static void ctx_rcu_free(struct rcu_head *head)
 {
        struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
-       unsigned nr_events = ctx->max_reqs;
-
        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);
-       }
 }
 
 /* __put_ioctx
@@ -217,6 +208,7 @@ static void ctx_rcu_free(struct rcu_head *head)
  */
 static void __put_ioctx(struct kioctx *ctx)
 {
+       unsigned nr_events = ctx->max_reqs;
        BUG_ON(ctx->reqs_active);
 
        cancel_delayed_work(&ctx->wq);
@@ -224,6 +216,12 @@ static void __put_ioctx(struct kioctx *ctx)
        aio_free_ring(ctx);
        mmdrop(ctx->mm);
        ctx->mm = NULL;
+       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);
+       }
        pr_debug("__put_ioctx: freeing %p\n", ctx);
        call_rcu(&ctx->rcu_head, ctx_rcu_free);
 }
@@ -247,7 +245,6 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 {
        struct mm_struct *mm;
        struct kioctx *ctx;
-       int did_sync = 0;
        int err = -ENOMEM;
 
        /* Prevent overflows */
@@ -257,7 +254,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
                return ERR_PTR(-EINVAL);
        }
 
-       if ((unsigned long)nr_events > aio_max_nr)
+       if (!nr_events || (unsigned long)nr_events > aio_max_nr)
                return ERR_PTR(-EAGAIN);
 
        ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
@@ -281,25 +278,14 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
                goto out_freectx;
 
        /* limit the number of system wide aios */
-       do {
-               spin_lock_bh(&aio_nr_lock);
-               if (aio_nr + nr_events > aio_max_nr ||
-                   aio_nr + nr_events < aio_nr)
-                       ctx->max_reqs = 0;
-               else
-                       aio_nr += ctx->max_reqs;
+       spin_lock_bh(&aio_nr_lock);
+       if (aio_nr + nr_events > aio_max_nr ||
+           aio_nr + nr_events < aio_nr) {
                spin_unlock_bh(&aio_nr_lock);
-               if (ctx->max_reqs || did_sync)
-                       break;
-
-               /* wait for rcu callbacks to have completed before giving up */
-               synchronize_rcu();
-               did_sync = 1;
-               ctx->max_reqs = nr_events;
-       } while (1);
-
-       if (ctx->max_reqs == 0)
                goto out_cleanup;
+       }
+       aio_nr += ctx->max_reqs;
+       spin_unlock_bh(&aio_nr_lock);
 
        /* now link into global list. */
        spin_lock(&mm->ioctx_lock);