Re: regression in page writeback

Andrew Morton
2009-09-23T00:55:52Z

On Wed, 23 Sep 2009 08:22:20 +0800 Wu Fengguang <fengguang.wu@intel.com> wrote:

> Jens' per-bdi writeback has another improvement. In 2.6.31, when
> superblocks A and B both have 100000 dirty pages, it will first
> exhaust A's 100000 dirty pages before going on to sync B's.

That would only be true if someone broke 2.6.31. Did they?

SYSCALL_DEFINE0(sync)
{
wakeup_pdflush(0);
sync_filesystems(0);
sync_filesystems(1);
if (unlikely(laptop_mode))
laptop_sync_completion();
return 0;
}

the sync_filesystems(0) is supposed to non-blockingly start IO against
all devices. It used to do that correctly. But people mucked with it
so perhaps it no longer does.