aio: percpu ioctx refcount

This just converts the ioctx refcount to the new generic dynamic percpu
refcount code.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

1 files changed, 27 insertions, 39 deletions

diff --git a/fs/aio.c b/fs/aio.c
index bb1a6c433110..7b470bfbf891 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -39,6 +39,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/migrate.h>
 #include <linux/ramfs.h>
+#include <linux/percpu-refcount.h>
 
 #include <asm/kmap_types.h>
 #include <asm/uaccess.h>
@@ -70,7 +71,7 @@ struct kioctx_cpu {
 };
 
 struct kioctx {
-        atomic_t                users;
+        struct percpu_ref       users;
         atomic_t                dead;
 
         /* This needs improving */
@@ -103,7 +104,7 @@ struct kioctx {
         long                    nr_pages;
 
         struct rcu_head         rcu_head;
-        struct work_struct      rcu_work;
+        struct work_struct      free_work;
 
         struct {
                 /*
@@ -403,8 +404,9 @@ static void free_ioctx_rcu(struct rcu_head *head)
  * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
  * now it's safe to cancel any that need to be.
  */
-static void free_ioctx(struct kioctx *ctx)
+static void free_ioctx(struct work_struct *work)
 {
+        struct kioctx *ctx = container_of(work, struct kioctx, free_work);
         struct aio_ring *ring;
         struct io_event res;
         struct kiocb *req;
@@ -462,10 +464,12 @@ static void free_ioctx(struct kioctx *ctx)
         call_rcu(&ctx->rcu_head, free_ioctx_rcu);
 }
 
-static void put_ioctx(struct kioctx *ctx)
+static void free_ioctx_ref(struct percpu_ref *ref)
 {
-        if (unlikely(atomic_dec_and_test(&ctx->users)))
-                free_ioctx(ctx);
+        struct kioctx *ctx = container_of(ref, struct kioctx, users);
+
+        INIT_WORK(&ctx->free_work, free_ioctx);
+        schedule_work(&ctx->free_work);
 }
 
 /* ioctx_alloc
@@ -505,8 +509,9 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 
         ctx->max_reqs = nr_events;
 
-        atomic_set(&ctx->users, 2);
-        atomic_set(&ctx->dead, 0);
+        if (percpu_ref_init(&ctx->users, free_ioctx_ref))
+                goto out_freectx;
+
         spin_lock_init(&ctx->ctx_lock);
         spin_lock_init(&ctx->completion_lock);
         mutex_init(&ctx->ring_lock);
@@ -516,7 +521,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 
         ctx->cpu = alloc_percpu(struct kioctx_cpu);
         if (!ctx->cpu)
-                goto out_freectx;
+                goto out_freeref;
 
         if (aio_setup_ring(ctx) < 0)
                 goto out_freepcpu;
@@ -535,6 +540,8 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
         aio_nr += ctx->max_reqs;
         spin_unlock(&aio_nr_lock);
 
+        percpu_ref_get(&ctx->users); /* io_setup() will drop this ref */
+
         /* now link into global list. */
         spin_lock(&mm->ioctx_lock);
         hlist_add_head_rcu(&ctx->list, &mm->ioctx_list);
@@ -549,6 +556,8 @@ out_cleanup:
         aio_free_ring(ctx);
 out_freepcpu:
         free_percpu(ctx->cpu);
+out_freeref:
+        free_percpu(ctx->users.pcpu_count);
 out_freectx:
         if (ctx->aio_ring_file)
                 fput(ctx->aio_ring_file);
@@ -557,22 +566,6 @@ out_freectx:
         return ERR_PTR(err);
 }
 
-static void kill_ioctx_work(struct work_struct *work)
-{
-        struct kioctx *ctx = container_of(work, struct kioctx, rcu_work);
-
-        wake_up_all(&ctx->wait);
-        put_ioctx(ctx);
-}
-
-static void kill_ioctx_rcu(struct rcu_head *head)
-{
-        struct kioctx *ctx = container_of(head, struct kioctx, rcu_head);
-
-        INIT_WORK(&ctx->rcu_work, kill_ioctx_work);
-        schedule_work(&ctx->rcu_work);
-}
-
 /* kill_ioctx
  *      Cancels all outstanding aio requests on an aio context.  Used
  *      when the processes owning a context have all exited to encourage
@@ -582,6 +575,8 @@ static void kill_ioctx(struct kioctx *ctx)
 {
         if (!atomic_xchg(&ctx->dead, 1)) {
                 hlist_del_rcu(&ctx->list);
+                /* percpu_ref_kill() will do the necessary call_rcu() */
+                wake_up_all(&ctx->wait);
 
                 /*
                  * It'd be more correct to do this in free_ioctx(), after all
@@ -598,8 +593,7 @@ static void kill_ioctx(struct kioctx *ctx)
                 if (ctx->mmap_size)
                         vm_munmap(ctx->mmap_base, ctx->mmap_size);
 
-                /* Between hlist_del_rcu() and dropping the initial ref */
-                call_rcu(&ctx->rcu_head, kill_ioctx_rcu);
+                percpu_ref_kill(&ctx->users);
         }
 }
 
@@ -633,12 +627,6 @@ void exit_aio(struct mm_struct *mm)
         struct hlist_node *n;
 
         hlist_for_each_entry_safe(ctx, n, &mm->ioctx_list, list) {
-                if (1 != atomic_read(&ctx->users))
-                        printk(KERN_DEBUG
-                                "exit_aio:ioctx still alive: %d %d %d\n",
-                                atomic_read(&ctx->users),
-                                atomic_read(&ctx->dead),
-                                atomic_read(&ctx->reqs_available));
                 /*
                  * We don't need to bother with munmap() here -
                  * exit_mmap(mm) is coming and it'll unmap everything.
@@ -757,7 +745,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
 
         hlist_for_each_entry_rcu(ctx, &mm->ioctx_list, list) {
                 if (ctx->user_id == ctx_id) {
-                        atomic_inc(&ctx->users);
+                        percpu_ref_get(&ctx->users);
                         ret = ctx;
                         break;
                 }
@@ -1054,7 +1042,7 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
                 ret = put_user(ioctx->user_id, ctxp);
                 if (ret)
                         kill_ioctx(ioctx);
-                put_ioctx(ioctx);
+                percpu_ref_put(&ioctx->users);
         }
 
 out:
@@ -1072,7 +1060,7 @@ SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
         struct kioctx *ioctx = lookup_ioctx(ctx);
         if (likely(NULL != ioctx)) {
                 kill_ioctx(ioctx);