linux-kernel - Re: [PATCH] cifs: Fix cifs readv callback merge resolution issue

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Message-ID: <CAHk-=wiVC5Cgyz6QKXFu6fTaA6h4CjexDR-OV9kL6Vo5x9v8=A@mail.gmail.com>
Date: Mon, 16 Sep 2024 16:08:10 +0200
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Howells <dhowells@...hat.com>
Cc: Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Steve French <stfrench@...rosoft.com>
Subject: Re: [PATCH] cifs: Fix cifs readv callback merge resolution issue

On Mon, 16 Sept 2024 at 15:50, David Howells <dhowells@...hat.com> wrote:
>
> Fix this so that it is "false".  The callback to netfslib in both SMB1 and
> SMB2/3 now gets offloaded from the network message thread to a separate
> worker thread and thus it's fine to do the slow work in this thread.

Note that with this fixed, now *every* direct call of
netfs_read_subreq_terminated() has that 'was_aync' as false.

The exception ends up being the netfs_read_cache_to_pagecache() thing,
which does that 'cres->ops->read()' with
netfs_read_subreq_terminated() as a callback function. And that
callback ends up being done with ki->was_async, which is actually set
unconditionally to 'true' (except for the immediate failure case which
then sets it to false after all).

Could we please just remove that whole 'was_async' case entirely, and
just make the cres->ops->read() path just do a workqueue (which seems
to be what the true case does anyway)?

So then the netfs_read_subreq_terminated() wouldn't need to take that
pointless argument, with the only case of async use just fixing
itself? Wouldn't that be cleaner?

             Linus