linux-kernel - Re: [PATCH v3] NFS: Fixup allocation flags for nfsiod's __GFP

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Message-ID: <BAD83C9F-5F54-4E8C-AC57-A3DE51A9227D@redhat.com>
Date: Thu, 10 Jul 2025 06:42:38 -0400
From: Benjamin Coddington <bcodding@...hat.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>,
 linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 Laurence Oberman <loberman@...hat.com>, Jeff Layton <jlayton@...nel.org>
Subject: Re: [PATCH v3] NFS: Fixup allocation flags for nfsiod's __GFP_NORETRY

On 10 Jul 2025, at 3:21, Christoph Hellwig wrote:

> On Wed, Jul 09, 2025 at 09:47:43PM -0400, Benjamin Coddington wrote:
>> If the NFS client is doing writeback from a workqueue context, avoid using
>> __GFP_NORETRY for allocations if the task has set PF_MEMALLOC_NOIO or
>> PF_MEMALLOC_NOFS.  The combination of these flags makes memory allocation
>> failures much more likely.
>
> Can we take a step back and figre out why this blanket usage of
> __GFP_NORETRY exists at all?

Added in 515dcdcd48736 there's a decent explanation which boils down to: its
usually OK for nfsiod to have an allocation failure, we want it to fail
quickly and not get hung up waiting for an allocation.

Ben