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 19:29:39 -0800 [thread overview]
Message-ID: <36223c44-d23f-18be-186e-08bcfce496d2@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()?
OK, right, this is not going to work as-is.
Any of the remaining iov_iter_get_pages*() callers that do direct IO
(vmsplice, ceph, ...) will end up calling bio_release_pages(), which is
now unconditionally calling unpin_user_pages(). So this is just
completely broken.
And so, once again, I'm back to, "must convert the whole pile of
iov_iter_get_page*() callers at once".
Back to the drawing board.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2022-02-28 3:29 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
2022-02-28 3:29 ` John Hubbard [this message]
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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