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 17:15 ` 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
2022-10-28 17:02 ` David Howells
2022-10-28 17:09 ` Linus Torvalds
2022-10-30 8:12 ` [PATCH v2 01/12] get rid of unlikely() on page_copy_sane() calls Christoph Hellwig
2022-11-01 13:51 ` How to convert I/O iterators to iterators, sglists and RDMA lists Christoph Hellwig
2022-10-28 17:31 ` David Howells
2022-11-04 18:47 ` David Howells
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