Unused iocbs in a batch should not be accounted as active.

Since commit 080d676de095 ("aio: allocate kiocbs in batches") iocbs are
allocated in a batch during processing of first iocbs.  All iocbs in a
batch are automatically added to ctx->active_reqs list and accounted in
ctx->reqs_active.

If one (not the last one) of iocbs submitted by an user fails, further
iocbs are not processed, but they are still present in ctx->active_reqs
and accounted in ctx->reqs_active.  This causes process to stuck in a D
state in wait_for_all_aios() on exit since ctx->reqs_active will never
go down to zero.  Furthermore since kiocb_batch_free() frees iocb
without removing it from active_reqs list the list become corrupted
which may cause oops.

Fix this by removing iocb from ctx->active_reqs and updating
ctx->reqs_active in kiocb_batch_free().

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: stable@kernel.org   # 3.2
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 78c514cfd212d66b8e6311d4a25435be6493c26d..969beb0e22311a4f7e7f4155524709d5dd8269bf 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -476,14 +476,21 @@ static void kiocb_batch_init(struct kiocb_batch *batch, long total)
        batch->count = total;
 }
 
-static void kiocb_batch_free(struct kiocb_batch *batch)
+static void kiocb_batch_free(struct kioctx *ctx, struct kiocb_batch *batch)
 {
        struct kiocb *req, *n;
 
+       if (list_empty(&batch->head))
+               return;
+
+       spin_lock_irq(&ctx->ctx_lock);
        list_for_each_entry_safe(req, n, &batch->head, ki_batch) {
                list_del(&req->ki_batch);
+               list_del(&req->ki_list);
                kmem_cache_free(kiocb_cachep, req);
+               ctx->reqs_active--;
        }
+       spin_unlock_irq(&ctx->ctx_lock);
 }
 
 /*
@@ -1742,7 +1749,7 @@ long do_io_submit(aio_context_t ctx_id, long nr,
        }
        blk_finish_plug(&plug);
 
-       kiocb_batch_free(&batch);
+       kiocb_batch_free(ctx, &batch);
        put_ioctx(ctx);
        return i ? i : ret;
 }