From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Marciniszyn Subject: [PATCH 2/2] IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast() Date: Fri, 04 Oct 2013 09:29:12 -0400 Message-ID: <20131004132911.29162.55257.stgit@phlsvslse11.ph.intel.com> References: <20131004132821.29162.46169.stgit@phlsvslse11.ph.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131004132821.29162.46169.stgit-K+u1se/DcYrLESAwzcoQNrvm/XP+8Wra@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jan Kara List-Id: linux-rdma@vger.kernel.org From: Jan Kara Function 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. Cc: Roland Dreier Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Reviewed-by: Mike Marciniszyn Signed-off-by: Jan Kara --- drivers/infiniband/hw/qib/qib_user_sdma.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/drivers/infiniband/hw/qib/qib_user_sdma.c b/drivers/infiniband/hw/qib/qib_user_sdma.c index d0a0ea0..165aee2 100644 --- a/drivers/infiniband/hw/qib/qib_user_sdma.c +++ b/drivers/infiniband/hw/qib/qib_user_sdma.c @@ -594,8 +594,7 @@ static int qib_user_sdma_pin_pages(const struct qib_devdata *dd, else j = npages; - ret = get_user_pages(current, current->mm, addr, - j, 0, 1, pages, NULL); + ret = get_user_pages_fast(addr, j, 0, pages); if (ret != j) { i = 0; j = ret; @@ -1294,11 +1293,8 @@ int qib_user_sdma_writev(struct qib_ctxtdata *rcd, int mxp = 8; int ndesc = 0; - down_write(¤t->mm->mmap_sem); ret = qib_user_sdma_queue_pkts(dd, ppd, pq, iov, dim, &list, &mxp, &ndesc); - up_write(¤t->mm->mmap_sem); - if (ret < 0) goto done_unlock; else { -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html