Re: [PATCH] VM: Fix the gfp_mask in invalidate_complete_page2

[Steve Dickson <SteveD@redhat.com>]

Trond Myklebust wrote:
> If try_to_release_page() is called with a zero gfp mask, then the
> filesystem is effectively denied the possibility of sleeping while
> attempting to release the page. There doesn't appear to be any valid
> reason why this should be banned, given that we're not calling this from
> a memory allocation context.
>  
> For this reason, change the gfp_mask argument of the call to GFP_KERNEL.
>     
> Note: I am less sure of what the callers of invalidate_complete_page()
> require, and so this patch does not touch that mask.
> 
> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> ---
> diff --git a/mm/truncate.c b/mm/truncate.c
> index f4edbc1..49c1ffd 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -302,7 +302,7 @@ invalidate_complete_page2(struct address
>  	if (page->mapping != mapping)
>  		return 0;
>  
> -	if (PagePrivate(page) && !try_to_release_page(page, 0))
> +	if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
>  		return 0;
>  
>  	write_lock_irq(&mapping->tree_lock);
Well I was using mapping_gfp_mask(mapping) as the argument to
try_to_release_page() which also worked... but isn't this
just plugging one of many holes? Meaning try_to_release_page is called
from a number of places with a zero gfp_mask so shouldn't those
also be fixed as well OR removed the gfp_mask as an argument as the
comment at the top of try_to_release_page() alludes to?

steved.