On Thu, Feb 21, 2013 at 10:22:19AM +0800, Shaohua Li wrote:
> Sorry if you receive this one twice, last mail get mail address messed.
>
> In swapin_readahead(), read_swap_cache_async() can read a bad swap entry,
> because we don't check if readahead swap entry is bad. This doesn't break
> anything but such swapin page is wasteful and can only be freed at page
> reclaim. We avoid read such swap entry.
>
Acked-by: Rafael Aquini <aquini@xxxxxxxxxx>
> And next patch will mark a swap entry bad temporarily for discard. Without this
> patch, swap entry count will be messed.
>
> Thanks Hugh to inspire swapin_readahead could use bad swap entry.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> mm/swapfile.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> Index: linux/mm/swapfile.c
> ===================================================================
> --- linux.orig/mm/swapfile.c 2013-02-18 15:21:09.285317914 +0800
> +++ linux/mm/swapfile.c 2013-02-18 15:21:34.545004083 +0800
> @@ -2374,6 +2374,11 @@ static int __swap_duplicate(swp_entry_t
> goto unlock_out;
>
> count = p->swap_map[offset];
> + if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
> + err = -ENOENT;
> + goto unlock_out;
> + }
> +
> has_cache = count & SWAP_HAS_CACHE;
> count &= ~SWAP_HAS_CACHE;
> err = 0;
>
> --
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