Re: [PATCH 2/8] xfs: Warn if direct reclaim tries to writeback pages

Christoph Hellwig
2011-07-24T11:32:10Z

On Thu, Jul 21, 2011 at 05:28:44PM +0100, Mel Gorman wrote:
> --- a/fs/xfs/linux-2.6/xfs_aops.c
> +++ b/fs/xfs/linux-2.6/xfs_aops.c
> @@ -930,12 +930,13 @@ xfs_vm_writepage(
> * random callers for direct reclaim or memcg reclaim. We explicitly
> * allow reclaim from kswapd as the stack usage there is relatively low.
> *
> - * This should really be done by the core VM, but until that happens
> - * filesystems like XFS, btrfs and ext4 have to take care of this
> - * by themselves.
> + * This should never happen except in the case of a VM regression so
> + * warn about it.
> */
> - if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC)
> + if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC) {
> + WARN_ON_ONCE(1);
> goto redirty;

The nicer way to write this is

if (WARN_ON(current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC)
goto redirty;