Messages in this thread Patch in this message | | | Date | Wed, 6 Jun 2012 16:50:09 +0200 | From | Oleg Nesterov <> | Subject | [PATCH v2 2/3] uprobes: change build_map_info() to try kmalloc(GFP_NOWAIT) first |
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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> --- 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 a1bbcab..88e903d 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -771,6 +771,16 @@ 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; -- 1.5.5.1
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