linux-kernel - [062/129] Unused iocbs in a batch should not be accounted as active.

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Date:	Mon, 23 Jan 2012 18:34:42 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Gleb Natapov <gleb@...hat.com>
Subject: [062/129] Unused iocbs in a batch should not be accounted as active.

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
Content-Length: 1954
Lines: 64

From: Gleb Natapov <gleb@...hat.com>

commit 69e4747ee9727d660b88d7e1efe0f4afcb35db1b upstream.

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@...hat.com>
Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/aio.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/aio.c
+++ b/fs/aio.c
@@ -476,14 +476,21 @@ static void kiocb_batch_init(struct kioc
 	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,
 	}
 	blk_finish_plug(&plug);

-	kiocb_batch_free(&batch);
+	kiocb_batch_free(ctx, &batch);
 	put_ioctx(ctx);
 	return i ? i : ret;
 }

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