From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
David Howells <dhowells@redhat.com>,
willy@infradead.org, dchinner@redhat.com,
Steve French <smfrench@gmail.com>,
Shyam Prasad N <nspmangalore@gmail.com>,
Rohith Surabattula <rohiths.msft@gmail.com>,
Jeff Layton <jlayton@kernel.org>, Ira Weiny <ira.weiny@intel.com>,
linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 12/12] use less confusing names for iov_iter direction initializers
Date: Fri, 28 Oct 2022 20:30:54 +0100 [thread overview]
Message-ID: <Y1wt7uzL7vkBQ6Vm@ZenIV> (raw)
In-Reply-To: <CAHk-=wi_iDAugqFZxTiscsRCNbtARMFiugWtBKO=NqgM-vCVAQ@mail.gmail.com>
On Fri, Oct 28, 2022 at 11:35:06AM -0700, Linus Torvalds wrote:
> > Umm... How are you going to e.g. copy from ITER_DISCARD? I've no problem
> > with WARN_ON_ONCE(), but when the operation really can't be done, what
> > can we do except returning an error?
>
> Fair enough. But it's the "people got the direction wrong, but the
> code worked" case that I would want tyo make sure still works - just
> with a warning.
>
> Clearly the ITER_DISCARD didn't work before either, but all the cases
> in patches 1-10 were things that _worked_, just with entirely the
> wrong ->data_source (aka iov_iter_rw()) value.
>
> So things like copy_to_iter() should warn if it's not a READ (or
> ITER_DEST), but it should still copy into the destination described by
> the iter, in order to keep broken code working.
>
> That's simply because I worry that your patches 1-10 didn't actually
> catch every single case. I'm not actually sure how you found them all
> - did you have some automation, or was it with "boot and find warnings
> from the first version of patch 11/12"?
Went through the callers, replaced each with the right ITER_... (there's
not that many of them and they are fairly easy to review), then went
through mismatches and split their fixups into the beginning of the
series (READ -> ITER_SOURCE becoming READ -> WRITE -> ITER_SOURCE, that
is).
FWIW, there used to be one case where we really tried to copy the wrong
way - fixed a couple of cycles ago (f615625a44c4 "9p: handling Rerror
without copy_from_iter_full()"). No such catches this time...
next prev parent reply other threads:[~2022-10-28 19:31 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-14 15:26 How to convert I/O iterators to iterators, sglists and RDMA lists David Howells
2022-10-17 13:15 ` Christoph Hellwig
2022-10-20 14:03 ` David Howells
2022-10-21 3:30 ` Ira Weiny
2022-10-24 14:51 ` Christoph Hellwig
2022-10-24 14:57 ` Christoph Hellwig
2022-10-24 19:53 ` Al Viro
2022-10-28 2:33 ` [PATCH v2 01/12] get rid of unlikely() on page_copy_sane() calls Al Viro
2022-10-28 2:33 ` [PATCH v2 02/12] csum_and_copy_to_iter(): handle ITER_DISCARD Al Viro
2022-10-28 2:33 ` [PATCH v2 03/12] [s390] copy_oldmem_kernel() - WRITE is "data source", not destination Al Viro
2022-10-28 2:33 ` [PATCH v2 04/12] [fsi] " Al Viro
2022-10-28 2:33 ` [PATCH v2 05/12] [infiniband] READ is "data destination", not source Al Viro
2022-10-28 2:33 ` [PATCH v2 06/12] [s390] zcore: WRITE is "data source", not destination Al Viro
2022-10-28 2:33 ` [PATCH v2 07/12] [s390] memcpy_real(): " Al Viro
2022-10-28 2:33 ` [PATCH v2 08/12] [target] fix iov_iter_bvec() "direction" argument Al Viro
2022-10-28 2:33 ` [PATCH v2 09/12] [vhost] fix 'direction' argument of iov_iter_{init,bvec}() Al Viro
2022-10-28 2:33 ` [PATCH v2 10/12] [xen] fix "direction" argument of iov_iter_kvec() Al Viro
2022-10-28 12:48 ` John Stoffel
2022-10-28 12:49 ` John Stoffel
2022-10-28 2:33 ` [PATCH v2 11/12] iov_iter: saner checks for attempt to copy to/from iterator Al Viro
2022-10-28 2:33 ` [PATCH v2 12/12] use less confusing names for iov_iter direction initializers Al Viro
2022-10-28 16:41 ` Linus Torvalds
2022-10-28 17:02 ` David Howells
2022-10-28 17:09 ` Linus Torvalds
2022-10-28 17:15 ` Al Viro
2022-10-28 18:35 ` Linus Torvalds
2022-10-28 19:30 ` Al Viro [this message]
2022-10-28 20:34 ` Linus Torvalds
2022-10-30 5:01 ` Al Viro
2022-10-30 8:12 ` [PATCH v2 01/12] get rid of unlikely() on page_copy_sane() calls Christoph Hellwig
2022-10-28 17:31 ` How to convert I/O iterators to iterators, sglists and RDMA lists David Howells
2022-11-04 18:47 ` David Howells
2022-11-01 13:51 ` Christoph Hellwig
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=Y1wt7uzL7vkBQ6Vm@ZenIV \
--to=viro@zeniv.linux.org.uk \
--cc=dchinner@redhat.com \
--cc=dhowells@redhat.com \
--cc=hch@infradead.org \
--cc=ira.weiny@intel.com \
--cc=jlayton@kernel.org \
--cc=linux-cifs@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=nspmangalore@gmail.com \
--cc=rohiths.msft@gmail.com \
--cc=smfrench@gmail.com \
--cc=torvalds@linux-foundation.org \
--cc=willy@infradead.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.