Hi,
On (11/14/14 09:49), Minchan Kim 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 [1].
>
> 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
> bio->bi_end_io.
>
> 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 [1]'s
> mentioned
>
> [1] zram: make rw_page opeartion return 0
>
> Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
> Cc: Karam Lee <karam.lee@xxxxxxx>
> Cc: Dave Chinner <david@xxxxxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> drivers/block/zram/zram_drv.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 4b4f4dbc3cfd..0e0650feab2a 100644
> --- 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,
> out_unlock:
> up_read(&zram->init_lock);
> out:
> - page_endio(page, rw, err);
> + if (unlikely(err))
> + return err;
this unlikely() case can be turned into a likely() one:
if (err == 0)
page_endio(page, rw, 0);
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;
> }
seems like we also can drop at least one goto (jump-to-return) for
invalid request.
(not sure about `goto out_unblock', yet another up_read(&zram->init_lock)
just will make function bigger).
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 0e0650f..decca6f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -956,8 +956,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
zram = bdev->bd_disk->private_data;
if (!valid_io_request(zram, sector, PAGE_SIZE)) {
atomic64_inc(&zram->stats.invalid_io);
- err = -EINVAL;
- goto out;
+ return -EINVAL;
}
down_read(&zram->init_lock);
@@ -974,15 +973,11 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
bv.bv_offset = 0;
err = zram_bvec_rw(zram, &bv, index, offset, rw);
-
out_unlock:
up_read(&zram->init_lock);
-out:
- if (unlikely(err))
- return err;
-
- page_endio(page, rw, 0);
- return 0;
+ if (err == 0)
+ page_endio(page, rw, 0);
+ return err;
}
static const struct block_device_operations zram_devops = {
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