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!
v2->v3:
some commit log and comment enhance per Huang, Ying
remove ref_initialized field
squash PATCH 1-2
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 (4):
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 | 14 ++++++--
mm/memory.c | 9 +++++
mm/shmem.c | 6 ++++
mm/swap_state.c | 6 ----
mm/swapfile.c | 79 +++++++++++++++++++++++++++-----------------
5 files changed, 76 insertions(+), 38 deletions(-)
--
2.19.1
