[PATCH 0/5] close various race windows for swap

[Miaohe Lin <linmiaohe@huawei.com>]

Hi all,
When I was investigating the swap code, I found some possible race
windows. This series aims to fix all these races. But using current
get/put_swap_device() to guard against concurrent swapoff for
swap_readpage() looks terrible because swap_readpage() may take really
long time. And to reduce the performance overhead on the hot-path as
much as possible, it appears we can use the percpu_ref to close this
race window(as suggested by Huang, Ying). The patch 1 adds percpu_ref
support for swap and the rest of the patches use this to close various
race windows. More details can be found in the respective changelogs.
Thanks!

Miaohe Lin (5):
  mm/swapfile: add percpu_ref support for swap
  swap: fix do_swap_page() race with swapoff
  mm/swap_state: fix get_shadow_from_swap_cache() race with swapoff
  mm/swap_state: fix potential faulted in race in swap_ra_info()
  mm/swap_state: fix swap_cluster_readahead() race with swapoff

 include/linux/swap.h |  4 +++-
 mm/memory.c          | 10 +++++++++
 mm/swap_state.c      | 33 +++++++++++++++++++++--------
 mm/swapfile.c        | 50 +++++++++++++++++++++++++++-----------------
 4 files changed, 68 insertions(+), 29 deletions(-)

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2.19.1