From: David Howells <dhowells@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: dhowells@redhat.com, linux-afs@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/24] iov_iter: Separate type from direction and use accessor functions
Date: Mon, 22 Oct 2018 14:00:45 +0100 [thread overview]
Message-ID: <10856.1540213245@warthog.procyon.org.uk> (raw)
In-Reply-To: <20181020045608.GH32577@ZenIV.linux.org.uk>
Al Viro <viro@ZenIV.linux.org.uk> wrote:
> One general comment: I would strongly recommend splitting the iov_iter
> initializers change into a separate patch.
Done.
> > void *addr = kmap_atomic(page);
> >
> > written = copy_to_iter(addr, copy, iter);
>
> FWIW, I wonder if that one is actually a missing primitive getting open-coded...
Ummm... You mean the combination of kmap_atomic() and copy_to_iter()? Can I
leave these for another time?
> > memcpy(&ctx->iter, iter, sizeof(struct iov_iter));
> > ctx->len = count;
> > iov_iter_advance(iter, count);
>
> ... and so, to much greater extent, is this.
And combining memcpy() and iov_iter_advance()?
> > - dio->should_dirty = (iter->type == ITER_IOVEC);
> > + dio->should_dirty = iter_is_iovec(iter);
>
> Nope. This path *can* get both read and write iov_iter. Not an equivalent
> change.
This should really have been (iter->type == (ITER_IOVEC | READ)).
Fixed to:
dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
> > - if (iter->type == ITER_IOVEC)
> > + if (iter_is_iovec(iter))
> > dio->flags |= IOMAP_DIO_DIRTY;
>
> Ditto.
This also should've had "| READ" in there.
Fixed to:
if (iter_is_iovec(iter) && iov_iter_rw(iter) == READ)
dio->flags |= IOMAP_DIO_DIRTY;
> > @@ -417,28 +417,35 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
> > int err;
> > struct iovec v;
> >
> > - if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
> > + switch (iov_iter_type(i)) {
> > + case ITER_IOVEC:
> > + case ITER_PIPE:
> > iterate_iovec(i, bytes, v, iov, skip, ({
> > err = fault_in_pages_readable(v.iov_base, v.iov_len);
> > if (unlikely(err))
> > return err;
> > 0;}))
> > + break;
> > + case ITER_KVEC:
> > + case ITER_BVEC:
> > + break;
> > }
> > return 0;
> > }
> > EXPORT_SYMBOL(iov_iter_fault_in_readable);
>
> Huh? That makes no sense whatsoever - ITER_PIPE ones are write-only in the
> first place, so they won't be passed to that one, but feeding ITER_PIPE to
> iterate_iovec() is insane. And even if they copy-from ITER_PIPES would
> appear, why the devil would we want to fault-in anything?
Note that the condition "!(i->type & (ITER_BVEC|ITER_KVEC))" is true if type
is ITER_PIPE or ITER_IOVEC.
That said, I can make it BUG if it encounters a pipe iterator.
> > @@ -987,7 +1003,7 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll)
> > return;
> > i->count += unroll;
> > - if (unlikely(i->type & ITER_PIPE)) {
> > + if (unlikely(iov_iter_is_pipe(i))) {
> > struct pipe_inode_info *pipe = i->pipe;
> ...
> > + case ITER_PIPE:
> > + BUG();
> > + }
> > }
> > EXPORT_SYMBOL(iov_iter_revert);
>
> Wha...?
It should never get to the BUG() because of the earlier if-statement.
However, the compiler gets picky sometimes, but isn't necessarily good enough
to see that this particular case should never occur, so to avoid getting a
warning about missing cases I put in a BUG. I can stick a comment on it and
make it just break.
David
next prev parent reply other threads:[~2018-10-22 13:00 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-20 1:10 [PATCH 00/24] AFS development David Howells
2018-10-20 1:10 ` [PATCH 01/24] iov_iter: Separate type from direction and use accessor functions David Howells
2018-10-20 4:56 ` Al Viro
2018-10-22 13:00 ` David Howells [this message]
2018-10-20 1:10 ` [PATCH 02/24] iov_iter: Renumber the ITER_* constants in uio.h David Howells
2018-10-20 4:59 ` Al Viro
2018-10-22 15:54 ` David Howells
2018-10-23 13:20 ` David Howells
2018-10-20 1:10 ` [PATCH 03/24] iov_iter: Add I/O discard iterator David Howells
2018-10-20 5:05 ` Al Viro
2018-10-22 16:18 ` David Howells
2018-10-20 1:11 ` [PATCH 04/24] afs: Better tracing of protocol errors David Howells
2018-10-20 1:11 ` [PATCH 05/24] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2018-10-20 1:11 ` [PATCH 06/24] afs: Improve FS server rotation error handling David Howells
2018-10-20 1:11 ` [PATCH 07/24] afs: Implement VL server rotation David Howells
2018-10-20 1:11 ` [PATCH 08/24] afs: Fix TTL on VL server and address lists David Howells
2018-10-20 1:11 ` [PATCH 09/24] afs: Handle EIO from delivery function David Howells
2018-10-20 1:11 ` [PATCH 10/24] afs: Add a couple of tracepoints to log I/O errors David Howells
2018-10-20 1:11 ` [PATCH 11/24] afs: Don't invoke the server to read data beyond EOF David Howells
2018-10-20 1:12 ` [PATCH 12/24] afs: Increase to 64-bit volume ID and 96-bit vnode ID for YFS David Howells
2018-10-20 1:12 ` [PATCH 13/24] afs: Commit the status on a new file/dir/symlink David Howells
2018-10-20 1:12 ` [PATCH 14/24] afs: Remove callback details from afs_callback_break struct David Howells
2018-10-20 1:12 ` [PATCH 15/24] afs: Implement the YFS cache manager service David Howells
2018-10-20 1:12 ` [PATCH 16/24] afs: Fix FS.FetchStatus delivery from updating wrong vnode David Howells
2018-10-20 1:12 ` [PATCH 17/24] afs: Calc callback expiry in op reply delivery David Howells
2018-10-20 1:12 ` [PATCH 18/24] afs: Get the target vnode in afs_rmdir() and get a callback on it David Howells
2018-10-20 1:12 ` [PATCH 19/24] afs: Expand data structure fields to support YFS David Howells
2018-10-20 1:13 ` [PATCH 20/24] afs: Implement YFS support in the fs client David Howells
2018-10-20 1:13 ` [PATCH 21/24] afs: Allow dumping of server cursor on operation failure David Howells
2018-10-20 1:13 ` [PATCH 22/24] afs: Eliminate the address pointer from the address list cursor David Howells
2018-10-20 1:13 ` [PATCH 23/24] afs: Fix callback handling David Howells
2018-10-20 1:13 ` [PATCH 24/24] afs: Probe multiple fileservers simultaneously David Howells
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=10856.1540213245@warthog.procyon.org.uk \
--to=dhowells@redhat.com \
--cc=linux-afs@lists.infradead.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).