On Wed, Apr 24, 2013 at 12:23:13PM -0700, Andrew Morton wrote:
> > } else {
> > + /*
> > + * In the case of swap-over-nfs, this can be a
> > + * temporary failure if the system has limited
> > + * memory for allocating transmit buffers.
> > + * Mark the page dirty and avoid
> > + * rotate_reclaimable_page but rate-limit the
> > + * messages but do not flag PageError like
> > + * the normal direct-to-bio case as it could
> > + * be temporary.
> > + */
> > set_page_dirty(page);
> > + ClearPageReclaim(page);
> > + if (printk_ratelimit()) {
> > + pr_err("Write-error on dio swapfile (%Lu)\n",
> > + (unsigned long long)page_file_offset(page));
> > + }
> > }
> > + end_page_writeback(page);
>
> A pox upon printk_ratelimit()! Both its code comment and the
> checkpatch warning explain why.
>
Ok. There were few sensible options around dealing with the write
errors. swap_writepage() could go to sleep on a waitqueue but it's
putting IO rate limiting where it doesn't belong. Retrying silently
forever could be difficult to debug if the error really is permanent.
> --- a/mm/page_io.c~mm-swap-mark-swap-pages-writeback-before-queueing-for-direct-io-fix
> +++ a/mm/page_io.c
> @@ -244,10 +244,8 @@ int __swap_writepage(struct page *page,
> */
> set_page_dirty(page);
> ClearPageReclaim(page);
> - if (printk_ratelimit()) {
> - pr_err("Write-error on dio swapfile (%Lu)\n",
> - (unsigned long long)page_file_offset(page));
> - }
> + pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
> + (unsigned long long)page_file_offset(page));
> }
> end_page_writeback(page);
> return ret;
>
> Do we need to cast the loff_t? afaict all architectures use long long.
> I didn't get a warning from sparc64 with the cast removed, and sparc64
> is the one which likes to use different underlying types.
>
> I think I'll remove it and wait for Fengguang's nastygram.
>
Sounds reasonable. I'll get cc'd on the same mails.
--
Mel Gorman
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>