Patch "rds: rds_ib_device.refcount overflow" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

rds: rds_ib_device.refcount overflow

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rds-rds_ib_device.refcount-overflow.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Wengang Wang <[email protected]>
Date: Mon, 6 Jul 2015 14:35:11 +0800
Subject: rds: rds_ib_device.refcount overflow

From: Wengang Wang <[email protected]>

commit 4fabb59449aa44a585b3603ffdadd4c5f4d0c033 upstream.

There lacks a dropping on rds_ib_device.refcount in case rds_ib_alloc_fmr failed(mr pool running out). this lead to the refcount overflow.

A complain in line 117(see following) is seen. From vmcore:
s_ib_rdma_mr_pool_depleted is 2147485544 and rds_ibdev->refcount is -2147475448. That is the evidence the mr pool is used up. so rds_ib_alloc_fmr is very likely to return ERR_PTR(-EAGAIN).

115 void rds_ib_dev_put(struct rds_ib_device *rds_ibdev) 116 {
117 BUG_ON(atomic_read(&rds_ibdev->refcount) <= 0);
118 if (atomic_dec_and_test(&rds_ibdev->refcount))
119 queue_work(rds_wq, &rds_ibdev->free_work);
120 }

fix is to drop refcount when rds_ib_alloc_fmr failed.

---
 net/rds/ib_rdma.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -759,8 +759,10 @@ void *rds_ib_get_mr(struct scatterlist *
 	}
 
 	ibmr = rds_ib_alloc_fmr(rds_ibdev);
-	if (IS_ERR(ibmr))
+	if (IS_ERR(ibmr)) {
+		rds_ib_dev_put(rds_ibdev);
 		return ibmr;
+	}
 
 	ret = rds_ib_map_fmr(rds_ibdev, ibmr, sg, nents);
 	if (ret == 0)

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/rds-rds_ib_device.refcount-overflow.patch