From 7a5bfb66b07f22d2429db776da7bb8b57bfb5cff Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 15 Jun 2012 17:43:36 +0200 Subject: [PATCH] uprobes: Change build_map_info() to try kmalloc(GFP_NOWAIT) first build_map_info() doesn't allocate the memory under i_mmap_mutex to avoid the deadlock with page reclaim. But it can try GFP_NOWAIT first, it should work in the likely case and thus we almost never need the pre-alloc-and-retry path. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju Acked-by: Peter Zijlstra Cc: Ananth N Mavinakayanahalli Cc: Anton Arapov Link: http://lkml.kernel.org/r/20120615154336.GA9588@redhat.com Signed-off-by: Ingo Molnar --- kernel/events/uprobes.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 4e0db3496d7..897417dbca8 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -761,6 +761,16 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register) if (!valid_vma(vma, is_register)) continue; + if (!prev && !more) { + /* + * Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through + * reclaim. This is optimistic, no harm done if it fails. + */ + prev = kmalloc(sizeof(struct map_info), + GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN); + if (prev) + prev->next = NULL; + } if (!prev) { more++; continue; -- 2.46.0