From: Jan Kara Date: Fri, 4 Oct 2013 13:29:06 +0000 (-0400) Subject: IB/ipath: Convert ipath_user_sdma_pin_pages() to use get_user_pages_fast() X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=eef5ed304aa7b49b8f58720855dd299163329db2;p=linux-edison.git IB/ipath: Convert ipath_user_sdma_pin_pages() to use get_user_pages_fast() commit 4adcf7fb6783e354aab38824d803fa8c4f8e8a27 upstream. ipath_user_sdma_queue_pkts() gets called with mmap_sem held for writing. Except for get_user_pages() deep down in ipath_user_sdma_pin_pages() we don't seem to need mmap_sem at all. Even more interestingly the function ipath_user_sdma_queue_pkts() (and also ipath_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 ipath_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. Signed-off-by: Jan Kara Signed-off-by: Mike Marciniszyn [ Merged in fix for call to get_user_pages_fast from Tetsuo Handa . - Roland ] Signed-off-by: Roland Dreier Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/infiniband/hw/ipath/ipath_user_sdma.c b/drivers/infiniband/hw/ipath/ipath_user_sdma.c index f5cb13b2144..cc04b7ba348 100644 --- a/drivers/infiniband/hw/ipath/ipath_user_sdma.c +++ b/drivers/infiniband/hw/ipath/ipath_user_sdma.c @@ -280,9 +280,7 @@ static int ipath_user_sdma_pin_pages(const struct ipath_devdata *dd, 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; @@ -811,10 +809,7 @@ int ipath_user_sdma_writev(struct ipath_devdata *dd, while (dim) { const int mxp = 8; - down_write(¤t->mm->mmap_sem); ret = ipath_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp); - up_write(¤t->mm->mmap_sem); - if (ret <= 0) goto done_unlock; else {