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Date: Tue, 18 Jun 2024 08:13:40 +0200
From: Christoph Hellwig <hch@lst.de>
To: Barry Song <21cnbao@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Trond Myklebust <trondmy@kernel.org>,
	Anna Schumaker <anna@kernel.org>, Steve French <sfrench@samba.org>,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	linux-mm@kvack.org, Barry Song <v-songbaohua@oppo.com>,
	Ryan Roberts <ryan.roberts@arm.com>
Subject: Re: [PATCH] nfs: fix nfs_swap_rw for large-folio swap
Message-ID: <20240618061340.GA28200@lst.de>
References: <20240614100329.1203579-1-hch@lst.de> <20240614100329.1203579-2-hch@lst.de> <20240614112148.cd1961e84b736060c54bdf26@linux-foundation.org> <CAGsJ_4wnWzoScqO9_NddHcDPbe_GbAiRFVm4w_H+QDmH=e=Rsw@mail.gmail.com> <20240616085436.GA28058@lst.de> <CAGsJ_4ytrnXJbfVi=PpTw34iBDqEoAm3b16oZr2VQpVWLmh5zA@mail.gmail.com> <20240617053201.GA16852@lst.de> <CAGsJ_4xQgY4kn46NO2=OWh2oDUj2F1-oYCRnKG4KCPJFfBT=Ng@mail.gmail.com> <20240618055253.GA27945@lst.de> <CAGsJ_4xMzU2N=c-vtLv+vJwSJFcADjdaUONc=8yDTm52QabOXw@mail.gmail.com>
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On Tue, Jun 18, 2024 at 06:05:33PM +1200, Barry Song wrote:
> Yes, that was exactly what I missed. I then figured it out, reproduced
> the issue,
> and discovered that the root cause was unrelated to large folios. It
> was actually
> due to a batched bio plugging optimization from 2022. You can find the new patch
> here:
> 
> https://lore.kernel.org/linux-mm/20240617220135.43563-1-21cnbao@gmail.com/

I don't really see any point in keeping the VM_BUG_ON.  The underlying
direct I/O code doesn't really care about the size at all.