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From: John Hubbard <jhubbard@nvidia.com>
To: Al Viro <viro@zeniv.linux.org.uk>, 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>, Miklos Szeredi <miklos@szeredi.hu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-mm@kvack.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/6] block, fs: assert that key paths use iovecs, and nothing else
Date: Sun, 27 Feb 2022 14:27:53 -0800	[thread overview]
Message-ID: <86ce63dd-f6b0-e7b9-c4e6-6b15dc8b32a0@nvidia.com> (raw)
In-Reply-To: <Yhv39J4+FwD/B2aJ@zeniv-ca.linux.org.uk>

On 2/27/22 14:15, Al Viro wrote:
> On Sun, Feb 27, 2022 at 01:34:31AM -0800, jhubbard.send.patches@gmail.com wrote:
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> Upcoming changes to Direct IO will change it from acquiring pages via
>> get_user_pages_fast(), to calling pin_user_pages_fast() instead.
>>
>> Place a few assertions at key points, that the pages are IOVEC (user
>> pages), to enforce the assumptions that there are no kernel or pipe or
>> other odd variations being passed.
> 
> Umm...  And what should happen when O_DIRECT file gets passed to splice()?

Hi Al,

First of all, full disclosure: I still haven't worked through how
splice() handles pages in all cases. I was hoping to defer it, by
limiting this series to not *all* of the original callers of
iov_iter_get_pages*().

This series leaves the splice() code pointing to iov_iter_get_pages(),
but maybe that's not possible after all.

Any advice or ideas about how to solve the O_DIRECT-to-splice() is very
welcome.


thanks,
-- 
John Hubbard
NVIDIA

  reply	other threads:[~2022-02-27 22:28 UTC|newest]

Thread overview: 21+ 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 [this message]
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
2022-03-01  9:41       ` Miklos Szeredi
2022-03-02  8:07         ` John Hubbard

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