aio: fix kioctx not being freed after cancellation at exit time

The recent changes overhauling fs/aio.c introduced a bug that results in the
kioctx not being freed when outstanding kiocbs are cancelled at exit_aio()
time.  Specifically, a kiocb that is cancelled has its completion events
discarded by batch_complete_aio(), which then fails to wake up the process
stuck in free_ioctx().  Fix this by removing the event suppression in
batch_complete_aio() and modify the wait_event() condition in free_ioctx()
appropriately.

This patch was tested with the cancel operation in the thread based code
posted yesterday.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Zach Brown <zab@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 39fd450de22d9c92ba1e0523c43705fe88e10ca8..0d9482bdf6c75d75e2322813d76620f83333fd89 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -349,7 +349,9 @@ static void free_ioctx(struct kioctx *ctx)
        kunmap_atomic(ring);
 
        while (atomic_read(&ctx->reqs_available) < ctx->nr_events - 1) {
-               wait_event(ctx->wait, head != ctx->shadow_tail);
+               wait_event(ctx->wait,
+                          (head != ctx->shadow_tail) ||
+                          (atomic_read(&ctx->reqs_available) >= ctx->nr_events - 1));
 
                avail = (head <= ctx->shadow_tail
                         ? ctx->shadow_tail : ctx->nr_events) - head;
@@ -774,17 +776,6 @@ void batch_complete_aio(struct batch_complete *batch)
                        n = rb_parent(n);
                }
 
-               if (unlikely(xchg(&req->ki_cancel,
-                                 KIOCB_CANCELLED) == KIOCB_CANCELLED)) {
-                       /*
-                        * Can't use the percpu reqs_available here - could race
-                        * with free_ioctx()
-                        */
-                       atomic_inc(&req->ki_ctx->reqs_available);
-                       aio_put_req(req);
-                       continue;
-               }
-
                if (unlikely(req->ki_eventfd != eventfd)) {
                        if (eventfd) {
                                /* Make event visible */