linux-kernel - [PATCH 2/3] uprobes: change build_map_info() to try kmalloc(GFP

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Message-ID: <20120604145315.GB6416@redhat.com>
Date:	Mon, 4 Jun 2012 16:53:15 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] 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@...hat.com>
---
 kernel/events/uprobes.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a1bbcab..c9836ae 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -772,8 +772,13 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
 			continue;
 
 		if (!prev) {
-			more++;
-			continue;
+			prev = kmalloc(sizeof(struct map_info),
+					GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
+			if (!prev) {
+				more++;
+				continue;
+			}
+			prev->next = NULL;
 		}
 
 		if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
-- 
1.5.5.1


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