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| author |   Kan Liang <kan.liang@intel.com> | 2017-08-02 13:32:27 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2017-08-02 17:16:13 -0700 |
| commit | 1ee1c3f5b5cff959e0ac95a125bd15eaf88cc638 (patch) | |
| tree | 18e5ee0fe0ccf7960c9e09eb51d968098fd420f1 /include | |
| parent | userfaultfd: non-cooperative: flush event_wqh at release time (diff) | |
| download | linux-dev-1ee1c3f5b5cff959e0ac95a125bd15eaf88cc638.tar.xz linux-dev-1ee1c3f5b5cff959e0ac95a125bd15eaf88cc638.zip | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/pagemap.h | 2 |
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()); |