aio: don't bother with unmapping when aio_free_ring() is coming from exit_aio()

... since exit_mmap() is coming and it will munmap() everything anyway.
In all other cases aio_free_ring() has ctx->mm == current->mm; moreover,
all other callers of vm_munmap() have mm == current->mm, so this will
allow us to get rid of mm argument of vm_munmap().

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

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 99bd790e8cd2..976e33d97413 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -92,8 +92,10 @@ static void aio_free_ring(struct kioctx *ctx)
         for (i=0; i<info->nr_pages; i++)
                 put_page(info->ring_pages[i]);
 
-        if (info->mmap_size)
+        if (info->mmap_size) {
+                BUG_ON(ctx->mm != current->mm);
                 vm_munmap(ctx->mm, info->mmap_base, info->mmap_size);
+        }
 
         if (info->ring_pages && info->ring_pages != info->internal_pages)
                 kfree(info->ring_pages);
@@ -386,6 +388,17 @@ void exit_aio(struct mm_struct *mm)
                                 "exit_aio:ioctx still alive: %d %d %d\n",
                                 atomic_read(&ctx->users), ctx->dead,
                                 ctx->reqs_active);
+                /*
+                 * We don't need to bother with munmap() here -
+                 * exit_mmap(mm) is coming and it'll unmap everything.
+                 * Since aio_free_ring() uses non-zero ->mmap_size
+                 * as indicator that it needs to unmap the area,
+                 * just set it to 0; aio_free_ring() is the only
+                 * place that uses ->mmap_size, so it's safe.
+                 * That way we get all munmap done to current->mm -
+                 * all other callers have ctx->mm == current->mm.
+                 */
+                ctx->ring_info.mmap_size = 0;
                 put_ioctx(ctx);
         }
 }