From: Mengmeng Zhao <mengmeng.zhao@linux.dev>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Dan Williams <djbw@kernel.org>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>,
tytso@mit.edu, Andreas Dilger <adilger.kernel@dilger.ca>,
Baokun Li <libaokun@linux.alibaba.com>,
Ojaswin Mujoo <ojaswin@linux.ibm.com>,
"Ritesh Harjani (IBM)" <ritesh.list@gmail.com>,
Zhang Yi <yi.zhang@huawei.com>,
"Darrick J. Wong" <djwong@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
asml.silence@gmail.com, Anuj Gupta <anuj1072538@gmail.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-mm@kvack.org, Li Wang <liwang@kylinos.cn>
Subject: Re: [RFC 2/6] mm/filemap: refuse dmabuf iterators in the generic read/write copy paths
Date: Mon, 9 Nov 2026 10:54:14 +0800 [thread overview]
Message-ID: <e483fc86-9a7e-49a5-873c-b5fb32d01848@linux.dev> (raw)
In-Reply-To: <20261106104205.GB5668@lst.de>
On 11/6/26 18:42, Christoph Hellwig wrote:
> On Thu, Nov 05, 2026 at 02:58:43PM +0800, Mengmeng Zhao wrote:
>> From: Mengmeng Zhao <zhaomengmeng@kylinos.cn>
>>
>> The generic copy helpers cannot touch device memory.
>
> Which generic copy helpers? This doesn't seem to touch copy_file_range
> at all.
>
Sorry for the inaccuracy, it refers to the buffered io patch in
generic_file_read_iter() and __generic_file_write_uter().
>> Refuse a
>> dmabuf iterator in generic_perform_write() and the filemap_read()
>> fallback while keeping any direct-I/O progress, and report a busy
>> folio from generic_file_direct_write() as -EAGAIN instead of asking
>> for the buffered fallback such an iterator cannot take.
>
> I suspect the fallback code in the callers might be a better stop
> for this.
>
Ok, I will put it in the callers side.
next prev parent reply other threads:[~2026-11-09 2:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 6:58 [RFC 0/6] ext4: Add dma-buf read/write support Mengmeng Zhao
2026-11-05 6:58 ` [RFC 1/6] block: refuse a dma-buf bio that carries a crypto context Mengmeng Zhao
2026-11-06 10:41 ` Christoph Hellwig
2026-11-09 2:51 ` Mengmeng Zhao
2026-11-05 6:58 ` [RFC 2/6] mm/filemap: refuse dmabuf iterators in the generic read/write copy paths Mengmeng Zhao
2026-11-06 10:42 ` Christoph Hellwig
2026-11-09 2:54 ` Mengmeng Zhao [this message]
2026-11-05 6:58 ` [RFC 3/6] dax: refuse dmabuf iterators in dax_iomap_rw() Mengmeng Zhao
2026-11-05 6:58 ` [RFC 4/6] iomap: refuse dmabuf iterators in iomap_file_buffered_write() Mengmeng Zhao
2026-11-05 6:58 ` [RFC 5/6] iomap: refuse dmabuf iterators on contents-encrypted inodes Mengmeng Zhao
2026-11-06 10:44 ` Christoph Hellwig
2026-11-09 2:56 ` Mengmeng Zhao
2026-11-05 6:58 ` [RFC 6/6] ext4: support dma-buf registered buffers for direct I/O Mengmeng Zhao
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