Commit-ID: 7a5bfb66b07f22d2429db776da7bb8b57bfb5cff
Gitweb: http://git.kernel.org/tip/7a5bfb66b07f22d2429db776da7bb8b57bfb5cff
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Fri, 15 Jun 2012 17:43:36 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 16 Jun 2012 09:10:44 +0200
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@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Anton Arapov <anton@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20120615154336.GA9588@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/uprobes.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4e0db34..897417d 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;
--
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