This is a note to let you know that I've just added the patch titled IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast() to the 3.4-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: ib-qib-convert-qib_user_sdma_pin_pages-to-use-get_user_pages_fast.patch and it can be found in the queue-3.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 603e7729920e42b3c2f4dbfab9eef4878cb6e8fa Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@xxxxxxx> Date: Fri, 4 Oct 2013 09:29:12 -0400 Subject: IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast() From: Jan Kara <jack@xxxxxxx> 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 <mike.marciniszyn@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Roland Dreier <roland@xxxxxxxxxxxxxxx> [Backported to 3.4: (Thank to Ben Hutchings) - Adjust context - Adjust indentation and nr_pages argument in qib_user_sdma_pin_pages()] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 { Patches currently in stable-queue which might be from jack@xxxxxxx are queue-3.4/ib-qib-convert-qib_user_sdma_pin_pages-to-use-get_user_pages_fast.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html