On 11/7/23 13:40, Sergey Senozhatsky wrote:
> On (23/11/07 16:39), Sergey Senozhatsky wrote:
>> Hmmm,
>> We may want to do more here. Basically, we probably need to re-confirm
>> after read_from_bdev() that the entry at index still has ZRAM_WB set
>> and, if so, that it points to the same blk_idx. IOW, check that it has
>> not been free-ed and re-used under us.
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1364,14 +1364,21 @@ static int zram_read_page(struct zram *zram, struct page *page, u32 index,
> ret = zram_read_from_zspool(zram, page, index);
> zram_slot_unlock(zram, index);
> } else {
> + unsigned long idx = zram_get_element(zram, index);
> /*
> * The slot should be unlocked before reading from the backing
> * device.
> */
> zram_slot_unlock(zram, index);
>
> - ret = read_from_bdev(zram, page, zram_get_element(zram, index),
> - parent);
> + ret = read_from_bdev(zram, page, idx, parent);
> + if (ret == 0) {
> + zram_slot_lock(zram, index);
> + if (!zram_test_flag(zram, index, ZRAM_WB) ||
> + idx != zram_get_element(zram, index))
> + ret = -EINVAL;
> + zram_slot_unlock(zram, index);
> + }
Why overwritten page can not be pushed to WB to the same blk_idx?
However I'm agree that this is VERY unlikely case, and this check is better than nothing.
