linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Pavel Begunkov <asml.silence@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [git pull] iov_iter fixes
Date: Thu, 9 Sep 2021 14:56:18 -0700	[thread overview]
Message-ID: <CAHk-=whoMLW-WP=8DikhfE4xAu_Tw9jDNkdab4RGEWWMagzW8Q@mail.gmail.com> (raw)
In-Reply-To: <ebc6cc5e-dd43-6370-b462-228e142beacb@kernel.dk>

On Thu, Sep 9, 2021 at 2:39 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> OK, one that I immediately found is just doing O_DIRECT to a block
> device or file on XFS. As pages are mapped and added, the iov_iter is
> advanced. If we then go and submit and get -EAGAIN, for example, then we
> return with what we mapped already consumed.

Ok, that's annoying but understandable. Dave points to a commit that
removes one of the EAGAIN cases, but apparently not some others.

I do kind of wonder if you can't have the exact same case when *some*
of the IO succeeds, though.

IOW, can't we have  that

        ret = io_iter_do_read(req, iter);

return partial success - and if XFS does that "update iovec on
failure", I could easily see that same code - or something else -
having done the exact same thing.

Put another way: if the iovec isn't guaranteed to be coherent when an
actual error occurs, then why would it be guaranteed to be coherent
with a partial success value?

Because in most cases - I'd argue pretty much all - those "partial
success" cases are *exactly* the same as the error cases, it's just
that we had a loop and one or more iterations succeeded before it hit
the error case.

Hmm?

            Linus

  reply	other threads:[~2021-09-09 21:56 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  4:22 [git pull] iov_iter fixes Al Viro
2021-09-09 19:37 ` Linus Torvalds
2021-09-09 21:19   ` Jens Axboe
2021-09-09 21:39     ` Jens Axboe
2021-09-09 21:56       ` Linus Torvalds [this message]
2021-09-09 22:21         ` Jens Axboe
2021-09-09 22:56           ` Linus Torvalds
2021-09-10  1:35             ` Jens Axboe
2021-09-10  2:43               ` Jens Axboe
2021-09-10  2:48               ` Al Viro
2021-09-10  3:06                 ` Jens Axboe
2021-09-10  3:15                   ` Al Viro
2021-09-10  3:23                     ` Jens Axboe
2021-09-10  3:24                     ` Al Viro
2021-09-10  3:28                       ` Jens Axboe
2021-09-13 15:29                 ` David Laight
2021-09-09 21:42     ` Dave Chinner
2021-09-10  2:57     ` Al Viro
2021-09-10  3:05       ` Jens Axboe
2021-09-10  3:11         ` Al Viro
2021-09-10  3:22           ` Jens Axboe
2021-09-10  3:27             ` Al Viro
2021-09-10  3:30               ` Jens Axboe
2021-09-10  3:36                 ` Al Viro
2021-09-10 13:57                   ` Jens Axboe
2021-09-10 14:42                     ` Al Viro
2021-09-10 15:08                       ` Jens Axboe
2021-09-10 15:32                         ` Al Viro
2021-09-10 15:36                           ` Jens Axboe
2021-09-10 15:04                     ` Jens Axboe
2021-09-10 16:06                       ` Jens Axboe
2021-09-10 16:44                         ` Linus Torvalds
2021-09-10 16:56                         ` Al Viro
2021-09-10 16:58                           ` Linus Torvalds
2021-09-10 17:26                             ` Jens Axboe
2021-09-10 17:31                               ` Linus Torvalds
2021-09-10 17:32                                 ` Jens Axboe
2021-09-10 18:48                                 ` Al Viro
2021-09-10 19:04                                   ` Linus Torvalds
2021-09-10 19:10                                     ` Linus Torvalds
2021-09-10 19:10                                   ` Jens Axboe
2021-09-10 17:04                           ` Jens Axboe
2021-09-09 22:54   ` Pavel Begunkov
2021-09-09 22:57     ` Pavel Begunkov
2021-09-09 23:14   ` Pavel Begunkov
2021-09-09 20:03 ` pr-tracker-bot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAHk-=whoMLW-WP=8DikhfE4xAu_Tw9jDNkdab4RGEWWMagzW8Q@mail.gmail.com' \
    --to=torvalds@linux-foundation.org \
    --cc=asml.silence@gmail.com \
    --cc=axboe@kernel.dk \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).