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-Tag: v3.2.54~142 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ecfc95da4f159e3a773bf1c0554e5f064bda491;p=pandora-kernel.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: Ben Hutchings --- Reading git-diff-tree failed