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SubjectRe: scheduling while atomic in z3fold
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On Mon, 2020-12-07 at 02:05 +0100, Vitaly Wool wrote:
>
> Could you please try the following patch in your setup:

crash> gdb list *z3fold_zpool_free+0x527
0xffffffffc0e14487 is in z3fold_zpool_free (mm/z3fold.c:341).
336 if (slots->slot[i]) {
337 is_free = false;
338 break;
339 }
340 }
341 write_unlock(&slots->lock); <== boom
342
343 if (is_free) {
344 struct z3fold_pool *pool = slots_to_pool(slots);
345
crash> z3fold_buddy_slots -x ffff99a3287b8780
struct z3fold_buddy_slots {
slot = {0xdeadbeef, 0xdeadbeef, 0xdeadbeef, 0xdeadbeef},
pool = 0xffff99a3146b8400,
lock = {
rtmutex = {
wait_lock = {
raw_lock = {
{
val = {
counter = 0x1
},
{
locked = 0x1,
pending = 0x0
},
{
locked_pending = 0x1,
tail = 0x0
}
}
}
},
waiters = {
rb_root = {
rb_node = 0xffff99a3287b8e00
},
rb_leftmost = 0x0
},
owner = 0xffff99a355c24500,
save_state = 0x1
},
readers = {
counter = 0x80000000
}
}
}

> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 18feaa0bc537..efe9a012643d 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -544,12 +544,17 @@ static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
> break;
> }
> }
> - if (!is_free)
> + if (!is_free) {
> set_bit(HANDLES_ORPHANED, &zhdr->slots->pool);
> - read_unlock(&zhdr->slots->lock);
> -
> - if (is_free)
> + read_unlock(&zhdr->slots->lock);
> + } else {
> + zhdr->slots->slot[0] =
> + zhdr->slots->slot[1] =
> + zhdr->slots->slot[2] =
> + zhdr->slots->slot[3] = 0xdeadbeef;
> + read_unlock(&zhdr->slots->lock);
> kmem_cache_free(pool->c_handle, zhdr->slots);
> + }
>
> if (locked)
> z3fold_page_unlock(zhdr);

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