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authorKan Liang <kan.liang@intel.com>2017-08-02 13:32:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-08-02 17:16:13 -0700
commit1ee1c3f5b5cff959e0ac95a125bd15eaf88cc638 (patch)
tree18e5ee0fe0ccf7960c9e09eb51d968098fd420f1
parent5a18b64e3f02125be1c0ef777501ae38aafe2a24 (diff)
mm: allow page_cache_get_speculative in interrupt context
Kernel panic when calling the IRQ-safe __get_user_pages_fast in NMI handler. The bug was introduced by commit 2947ba054a4d ("x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"). The original x86 __get_user_page_fast used plain get_page() or page_ref_add(). However, the generic __get_user_page_fast uses page_cache_get_speculative(), which has VM_BUG_ON(in_interrupt()). There is no reason to prevent page_cache_get_speculative from using in interrupt context. According to the author, putting a BUG_ON there is just because the code is not verifying correctness of interrupt races. I did some tests in interrupt context. There is no issue found. Removing VM_BUG_ON(in_interrupt()) for page_cache_get_speculative(). Link: http://lkml.kernel.org/r/1501609146-59730-1-git-send-email-kan.liang@intel.com Fixes: 2947ba054a4d ("x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation") Signed-off-by: Kan Liang <kan.liang@intel.com> Cc: Jens Axboe <axboe@fb.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Ying Huang <ying.huang@intel.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/pagemap.h2
1 files changed, 0 insertions, 2 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index baa9344dcd10..79b36f57c3ba 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -163,8 +163,6 @@ void release_pages(struct page **pages, int nr, bool cold);
*/
static inline int page_cache_get_speculative(struct page *page)
{
- VM_BUG_ON(in_interrupt());
-
#ifdef CONFIG_TINY_RCU
# ifdef CONFIG_PREEMPT_COUNT
VM_BUG_ON(!in_atomic() && !irqs_disabled());