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SubjectRe: [PATCH] mm: ratelimit end_swap_bio_write() error
On Sat 06-01-18 13:34:07, Sergey Senozhatsky wrote:
> Use the ratelimited printk() version for swap-device write error
> reporting. We can use ZRAM as a swap-device, and the tricky part
> here is that zsmalloc() stores compressed objects in memory, thus
> it has to allocates pages during swap-out. If the system is short
> on memory, then we begin to flood printk() log buffer with the
> same "Write-error on swap-device XXX" error messages and sometimes
> simply lockup the system.

Should we print an error in such a situation at all? Write-error
certainly sounds scare and it suggests something went really wrong.
My understading is that zram failed swap-out is not critical and
therefore the error message is not really useful. Or what should an
admin do when seeing it?

> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
> mm/page_io.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index e93f1a4cacd7..422cd49bcba8 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -63,7 +63,7 @@ void end_swap_bio_write(struct bio *bio)
> * Also clear PG_reclaim to avoid rotate_reclaimable_page()
> */
> set_page_dirty(page);
> - pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
> + pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n",
> MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
> (unsigned long long)bio->bi_iter.bi_sector);
> ClearPageReclaim(page);
> --
> 2.15.1

--
Michal Hocko
SUSE Labs

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