Re: [fuse-devel] [PATCH 14/14] mm: Account for WRITEBACK_TEMP in balance_dirty_pages

["Maxim V. Patlasov" <mpatlasov@parallels.com>]

Hi Miklos,

04/01/2013 02:42 PM, Maxim V. Patlasov пишет:
> Make balance_dirty_pages start the throttling when the WRITEBACK_TEMP
> counter is high enough. This prevents us from having too many dirty
> pages on fuse, thus giving the userspace part of it a chance to write
> stuff properly.
>
> Note, that the existing balance logic is per-bdi, i.e. if the fuse
> user task gets stuck in the function this means, that it either
> writes to the mountpoint it serves (but it can deadlock even without
> the writeback) or it is writing to some _other_ dirty bdi and in the
> latter case someone else will free the memory for it.
>
> Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
> ---
>   mm/page-writeback.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0713bfb..c47bcd4 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1235,7 +1235,8 @@ static void balance_dirty_pages(struct address_space *mapping,
>   		 */
>   		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
>   					global_page_state(NR_UNSTABLE_NFS);
> -		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
> +		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK) +
> +			global_page_state(NR_WRITEBACK_TEMP);
>   
>   		global_dirty_limits(&background_thresh, &dirty_thresh);

Please drop this patch. As we discussed in LSF/MM, the fix above is 
correct, but it's not enough: we also need to ensure disregard of 
NR_WRITEBACK_TEMP when balance_dirty_pages() is called from fuse daemon. 
I'll send a separate patch-set soon.

Thanks,
Maxim