[PATCH] zram: Failing to decompress is WARN_ON worthy

[PATCH] zram: Failing to decompress is WARN_ON worthy

[Douglas Anderson]

If we fail to decompress in zram it's a pretty serious problem.  We
were entrusted to be able to decompress the old data but we failed.
Either we've got some crazy bug in the compression code or we've got
memory corruption.

At the moment, when this happens the log looks like this:

  ERR kernel: [ 1833.099861] zram: Decompression failed! err=-22, page=336112
  ERR kernel: [ 1833.099881] zram: Decompression failed! err=-22, page=336112
  ALERT kernel: [ 1833.099886] Read-error on swap-device (253:0:2688896)

It is true that we have an "ALERT" level log in there, but (at least
to me) it feels like even this isn't enough to impart the seriousness
of this error.  Let's convert to a WARN_ON.  Note that WARN_ON is
automatically "unlikely" so we can simply replace the old annotation
with the new one.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 9100ac36670a..a6e2f0980aff 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1268,7 +1268,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
 	zram_slot_unlock(zram, index);
 
 	/* Should NEVER happen. Return bio error if it does. */
-	if (unlikely(ret))
+	if (WARN_ON(ret))
 		pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 
 	return ret;
-- 
2.28.0.681.g6f77f65b4e-goog

Re: [PATCH] zram: Failing to decompress is WARN_ON worthy

[Minchan Kim]

On Thu, Sep 17, 2020 at 05:41:20PM -0700, Douglas Anderson wrote:
> If we fail to decompress in zram it's a pretty serious problem.  We
> were entrusted to be able to decompress the old data but we failed.
> Either we've got some crazy bug in the compression code or we've got
> memory corruption.
> 
> At the moment, when this happens the log looks like this:
> 
>   ERR kernel: [ 1833.099861] zram: Decompression failed! err=-22, page=336112
>   ERR kernel: [ 1833.099881] zram: Decompression failed! err=-22, page=336112
>   ALERT kernel: [ 1833.099886] Read-error on swap-device (253:0:2688896)
> 
> It is true that we have an "ALERT" level log in there, but (at least
> to me) it feels like even this isn't enough to impart the seriousness
> of this error.  Let's convert to a WARN_ON.  Note that WARN_ON is
> automatically "unlikely" so we can simply replace the old annotation
> with the new one.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>