The patch titled
Subject: swap_readpage(): avoid blk_wake_io_task() if !synchronous
has been added to the -mm tree. Its filename is
swap_readpage-avoid-blk_wake_io_task-if-synchronous.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/swap_readpage-avoid-blk_wake_io_task-if-synchronous.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/swap_readpage-avoid-blk_wake_io_task-if-synchronous.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: swap_readpage(): avoid blk_wake_io_task() if !synchronous
swap_readpage() sets waiter = bio->bi_private even if synchronous = F,
this means that the caller can get the spurious wakeup after return. This
can be fatal if blk_wake_io_task() does set_current_state(TASK_RUNNING)
after the caller does set_special_state(), in the worst case the kernel
can crash in do_task_dead().
Link: http://lkml.kernel.org/r/20190704160301.GA5956@xxxxxxxxxx
Fixes: 0619317ff8baa2d ("block: add polled wakeup task helper")
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reported-by: Qian Cai <cai@xxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_io.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/mm/page_io.c~swap_readpage-avoid-blk_wake_io_task-if-synchronous
+++ a/mm/page_io.c
@@ -137,8 +137,10 @@ out:
unlock_page(page);
WRITE_ONCE(bio->bi_private, NULL);
bio_put(bio);
- blk_wake_io_task(waiter);
- put_task_struct(waiter);
+ if (waiter) {
+ blk_wake_io_task(waiter);
+ put_task_struct(waiter);
+ }
}
int generic_swapfile_activate(struct swap_info_struct *sis,
@@ -395,11 +397,12 @@ int swap_readpage(struct page *page, boo
* Keep this task valid during swap readpage because the oom killer may
* attempt to access it in the page fault retry time check.
*/
- get_task_struct(current);
- bio->bi_private = current;
bio_set_op_attrs(bio, REQ_OP_READ, 0);
- if (synchronous)
+ if (synchronous) {
bio->bi_opf |= REQ_HIPRI;
+ get_task_struct(current);
+ bio->bi_private = current;
+ }
count_vm_event(PSWPIN);
bio_get(bio);
qc = submit_bio(bio);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
swap_readpage-avoid-blk_wake_io_task-if-synchronous.patch
signal-simplify-set_user_sigmask-restore_user_sigmask.patch
select-change-do_poll-to-return-erestartnohand-rather-than-eintr.patch
select-shift-restore_saved_sigmask_unless-into-poll_select_copy_remaining.patch
aio-simplify-read_events.patch
