Re: [PATCH] sunrpc: convert unnecessary GFP_ATOMIC to GFP_NOFS

[Bruce Fields <bfields@fieldses.org>]

On Thu, Dec 20, 2018 at 10:47:25AM -0500, Chuck Lever wrote:
> 
> 
> > On Dec 20, 2018, at 10:42 AM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > 
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > It's OK to sleep here, we just don't want to recurse into the filesystem
> > as this writeout could be waiting on this.
> 
> "as a writeout"

Oops, thanks.

> > Future work: the documentation for GFP_NOFS says "Please try to avoid
> > using this flag directly and instead use memalloc_nofs_{save,restore} to
> > mark the whole scope which cannot/shouldn't recurse into the FS layer
> > with a short explanation why. All allocation requests will inherit
> > GFP_NOFS implicitly."
> > 
> > But I'm not sure where to do this.  Should the workqueue be arranging
> > that for us in the case of workqueues created with WQ_MEM_RECLAIM?
> 
> There seem to be plenty of uses of GFP_NOFS in NFS and sunrpc.
> That sounds like a big project.

Yeah, just noting it for future reference.

--b.

> > Reported-by: Trond Myklebust <trondmy@hammer.space>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > ---
> > net/sunrpc/rpcb_clnt.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > Also, I've still got this one.  (And still haven't looked into whether
> > it should be using a memalloc_nofs_{save,restore} elsewhere instead.)
> > 
> > diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
> > index 08b5fa4a2852..41a971ac1c63 100644
> > --- a/net/sunrpc/rpcb_clnt.c
> > +++ b/net/sunrpc/rpcb_clnt.c
> > @@ -752,7 +752,7 @@ void rpcb_getport_async(struct rpc_task *task)
> > 		goto bailout_nofree;
> > 	}
> > 
> > -	map = kzalloc(sizeof(struct rpcbind_args), GFP_ATOMIC);
> > +	map = kzalloc(sizeof(struct rpcbind_args), GFP_NOFS);
> > 	if (!map) {
> > 		status = -ENOMEM;
> > 		dprintk("RPC: %5u %s: no memory available\n",
> > @@ -770,7 +770,7 @@ void rpcb_getport_async(struct rpc_task *task)
> > 	case RPCBVERS_4:
> > 	case RPCBVERS_3:
> > 		map->r_netid = xprt->address_strings[RPC_DISPLAY_NETID];
> > -		map->r_addr = rpc_sockaddr2uaddr(sap, GFP_ATOMIC);
> > +		map->r_addr = rpc_sockaddr2uaddr(sap, GFP_NOFS);
> > 		if (!map->r_addr) {
> > 			status = -ENOMEM;
> > 			dprintk("RPC: %5u %s: no memory available\n",
> > -- 
> > 2.19.2
> > 
> 
> --
> Chuck Lever
> 
>