From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Roland Dreier" , "Jan Kara" , "Mike Marciniszyn" Date: Sun, 29 Dec 2013 03:08:43 +0100 Message-ID: Subject: [PATCH 3.2 044/185] IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast() In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.2.54-rc1 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 [bwh: Backported to 3.2: - Adjust context - Adjust indentation and nr_pages argument in qib_user_sdma_pin_pages()] Signed-off-by: Ben Hutchings --- 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 {