[PATCH v2 0/5] close various race windows for swap

From: Miaohe Lin
Date: Sat Apr 17 2021 - 05:41:58 EST


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 most of the remaining patches try to use this to
close various race windows. More details can be found in the respective
changelogs. Thanks!

v1->v2:
reorganize the patch-2/5
various enhance and fixup per Huang, Ying
Many thanks for the comments of Huang, Ying, Dennis Zhou and Tim Chen.

Miaohe Lin (5):
mm/swapfile: add percpu_ref support for swap
mm/swapfile: use percpu_ref to serialize against concurrent swapoff
swap: fix do_swap_page() race with swapoff
mm/swap: remove confusing checking for non_swap_entry() in
swap_ra_info()
mm/shmem: fix shmem_swapin() race with swapoff

include/linux/swap.h | 15 +++++++--
mm/memory.c | 9 ++++++
mm/shmem.c | 6 ++++
mm/swap_state.c | 6 ----
mm/swapfile.c | 74 +++++++++++++++++++++++++++-----------------
5 files changed, 73 insertions(+), 37 deletions(-)

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2.19.1