On Wed, Jun 29, 2016 at 02:47:20PM -0700, David Rientjes wrote: > It's possible to isolate some freepages in a pageblock and then fail > split_free_page() due to the low watermark check. In this case, we hit > VM_BUG_ON() because the freeing scanner terminated early without a > contended lock or enough freepages. > > This should never have been a VM_BUG_ON() since it's not a fatal > condition. It should have been a VM_WARN_ON() at best, or even handled > gracefully. > > Regardless, we need to terminate anytime the full pageblock scan was not > done. The logic belongs in isolate_freepages_block(), so handle its state > gracefully by terminating the pageblock loop and making a note to restart > at the same pageblock next time since it was not possible to complete the > scan this time. > > Reported-by: Minchan Kim <minchan@xxxxxxxxxx> > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> > --- > Note: I really dislike the low watermark check in split_free_page() and > consider it poor software engineering. The function should split a free > page, nothing more. Terminating memory compaction because of a low > watermark check when we're simply trying to migrate memory seems like an > arbitrary heuristic. There was an objection to removing it in the first > proposed patch, but I think we should really consider removing that > check so this is simpler. > > mm/compaction.c | 37 +++++++++++++++---------------------- > 1 file changed, 15 insertions(+), 22 deletions(-) <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read Documentation/stable_kernel_rules.txt for how to do this properly. </formletter> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html