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From: John Hubbard <jhubbard@nvidia.com>
To: Miklos Szeredi <miklos@szeredi.hu>, jhubbard.send.patches@gmail.com
Cc: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
	Christoph Hellwig <hch@infradead.org>,
	Dave Chinner <dchinner@redhat.com>,
	"Darrick J . Wong" <djwong@kernel.org>,
	Theodore Ts'o <tytso@mit.edu>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-xfs <linux-xfs@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] fuse: convert direct IO paths to use FOLL_PIN
Date: Mon, 28 Feb 2022 13:16:34 -0800	[thread overview]
Message-ID: <f0b158dc-5b01-67aa-1f49-331bf1ff2bfd@nvidia.com> (raw)
In-Reply-To: <CAJfpegsDkpdCQiPmfKfX_b4-bkkj5N5vRhseifEH6woJ7r0S6A@mail.gmail.com>

On 2/28/22 07:59, Miklos Szeredi wrote:
> On Sun, 27 Feb 2022 at 10:34, <jhubbard.send.patches@gmail.com> wrote:
>>
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> Convert the fuse filesystem to support the new iov_iter_get_pages()
>> behavior. That routine now invokes pin_user_pages_fast(), which means
>> that such pages must be released via unpin_user_page(), rather than via
>> put_page().
>>
>> This commit also removes any possibility of kernel pages being handled,
>> in the fuse_get_user_pages() call. Although this may seem like a steep
>> price to pay, Christoph Hellwig actually recommended it a few years ago
>> for nearly the same situation [1].
> 
> This might work for O_DIRECT, but fuse has this mode of operation
> which turns normal "buffered" I/O into direct I/O.  And that in turn
> will break execve of such files.
> 
> So AFAICS we need to keep kvec handing in some way.
> 

Thanks for bringing that up! Do you have any hints for me, to jump start
a deeper look? And especially, sample programs that exercise this?


thanks,
-- 
John Hubbard
NVIDIA

  reply	other threads:[~2022-02-28 21:16 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-27  9:34 [PATCH 0/6] block, fs: convert most Direct IO cases to FOLL_PIN jhubbard.send.patches
2022-02-27  9:34 ` [PATCH 1/6] mm/gup: introduce pin_user_page() jhubbard.send.patches
2022-02-27  9:34 ` [PATCH 2/6] iov_iter: new iov_iter_pin_pages*(), for FOLL_PIN pages jhubbard.send.patches
2022-02-27 21:57   ` Jens Axboe
2022-02-27 22:09     ` John Hubbard
2022-02-28 22:49     ` John Hubbard
2022-02-27  9:34 ` [PATCH 3/6] block, fs: assert that key paths use iovecs, and nothing else jhubbard.send.patches
2022-02-27 21:58   ` Jens Axboe
2022-02-27 22:12     ` John Hubbard
2022-02-27 22:15   ` Al Viro
2022-02-27 22:27     ` John Hubbard
2022-02-28  3:29     ` John Hubbard
2022-02-27  9:34 ` [PATCH 4/6] block, bio, fs: convert most filesystems to pin_user_pages_fast() jhubbard.send.patches
2022-02-27 21:59   ` Jens Axboe
2022-02-27 22:13     ` John Hubbard
2022-02-27  9:34 ` [PATCH 5/6] NFS: direct-io: convert to FOLL_PIN pages jhubbard.send.patches
2022-02-27  9:34 ` [PATCH 6/6] fuse: convert direct IO paths to use FOLL_PIN jhubbard.send.patches
2022-02-28 15:59   ` Miklos Szeredi
2022-02-28 21:16     ` John Hubbard [this message]
2022-03-01  9:41       ` Miklos Szeredi
2022-03-02  8:07         ` John Hubbard
2022-08-27  8:36 [PATCH 0/6] convert most filesystems to pin_user_pages_fast() John Hubbard
2022-08-27  8:36 ` [PATCH 6/6] fuse: convert direct IO paths to use FOLL_PIN John Hubbard

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