| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.12 060/212] IB/ipath: Convert ipath_user_sdma_pin_pages() to use get_user_pages_fast() | Date | Mon, 2 Dec 2013 11:14:11 -0800 |
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3.12-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara <jack@suse.cz>
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 <jack@suse.cz> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com> [ Merged in fix for call to get_user_pages_fast from Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>. - Roland ] Signed-off-by: Roland Dreier <roland@purestorage.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/infiniband/hw/ipath/ipath_user_sdma.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)
--- 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(con 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_ 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 {
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