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
next prev parent 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).