Commit 7a5bfb66 authored Jun 15, 2012 by Oleg Nesterov Committed by Ingo Molnar Jun 16, 2012

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 <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Link: http://lkml.kernel.org/r/20120615154336.GA9588@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 26872090

kernel/events/uprobes.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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;