From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mike Marciniszyn , Jan Kara , Roland Dreier , Ben Hutchings Subject: [PATCH 3.10 24/26] IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast() Date: Tue, 18 Feb 2014 14:47:20 -0800 Message-Id: <20140218224531.091301078@linuxfoundation.org> In-Reply-To: <20140218224530.398913499@linuxfoundation.org> References: <20140218224530.398913499@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit 603e7729920e42b3c2f4dbfab9eef4878cb6e8fa upstream. qib_user_sdma_queue_pkts() gets called with mmap_sem held for writing. Except for get_user_pages() deep down in qib_user_sdma_pin_pages() we don't seem to need mmap_sem at all. Even more interestingly the function qib_user_sdma_queue_pkts() (and also qib_user_sdma_coalesce() called somewhat later) call copy_from_user() which can hit a page fault and we deadlock on trying to get mmap_sem when handling that fault. So just make qib_user_sdma_pin_pages() use get_user_pages_fast() and leave mmap_sem locking for mm. This deadlock has actually been observed in the wild when the node is under memory pressure. Reviewed-by: Mike Marciniszyn Signed-off-by: Jan Kara Signed-off-by: Roland Dreier [Backported to 3.10: (Thanks to Ben Huthings) - Adjust context - Adjust indentation and nr_pages argument in qib_user_sdma_pin_pages()] Signed-off-by: Ben Hutchings Signed-off-by: Mike Marciniszyn Signed-off-by: Greg Kroah-Hartman --- drivers/infiniband/hw/qib/qib_user_sdma.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) --- a/drivers/infiniband/hw/qib/qib_user_sdma.c +++ b/drivers/infiniband/hw/qib/qib_user_sdma.c @@ -284,8 +284,7 @@ static int qib_user_sdma_pin_pages(const int j; int ret; - ret = get_user_pages(current, current->mm, addr, - npages, 0, 1, pages, NULL); + ret = get_user_pages_fast(addr, npages, 0, pages); if (ret != npages) { int i; @@ -830,10 +829,7 @@ int qib_user_sdma_writev(struct qib_ctxt while (dim) { const int mxp = 8; - down_write(¤t->mm->mmap_sem); ret = qib_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp); - up_write(¤t->mm->mmap_sem); - if (ret <= 0) goto done_unlock; else {