Re: [PATCH] zram: rely on the bi_end_io for zram_rw_page fails
From: Andrew Morton
Date: Tue Nov 18 2014 - 18:23:42 EST
On Fri, 14 Nov 2014 09:49:07 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote:
> When I tested zram, I found processes got segfaulted.
> The reason was zram_rw_page doesn't make the page dirty
> again when swap write failed, and even it doesn't return
> error by .
> If error by zram internal happens, zram_rw_page should return
> non-zero without calling page_endio.
> It causes resubmit the IO with bio so that it ends up calling
> The reason is zram could be used for a block device for FS and
> swap, which they uses different bio complete callback, which
> works differently. So, we should rely on the bio I/O complete
> handler rather than zram_bvec_rw itself in case of I/O fail.
> This patch fixes the segfault issue as well one 's
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -978,12 +978,10 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
> - page_endio(page, rw, err);
> + if (unlikely(err))
> + return err;
> - /*
> - * Return 0 prevents I/O fallback trial caused by rw_page fail
> - * and upper layer can handle this IO error via page error.
> - */
> + page_endio(page, rw, 0);
> return 0;
Losing the comment makes me sad. The code is somewhat odd-looking. We
should add some words explaining why we're not reporting errors at this
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