linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-efi@vger.kernel.org,
	Matthew Garrett <matthew.garrett@nebula.com>,
	Jeremy Kerr <jk@ozlabs.org>,
	Matt Fleming <matt.fleming@intel.com>
Subject: Re: efivarfs and writev() support
Date: Thu, 12 Mar 2015 06:34:37 +0000	[thread overview]
Message-ID: <20150312063437.GK29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <7F5112DD-6998-47D3-B6B9-5618E14E022A@holtmann.org>

On Wed, Mar 11, 2015 at 08:12:52AM -0700, Marcel Holtmann wrote:
> Hi Matt,
> 
> >> it seems that efivarfs only supports readv(), but when it comes to
> >> writev(), I am getting an error. Is there any reason to not support
> >> vectored write on this filesystem? Especially with the uint32 header
> >> for each file, I think it would make perfect sense to support it.
> > 
> > What error are you seeing? I thought that the vfs fell back to a looped
> > write if the file system doesn't support .write_iter()?
> 
> that seems to work for readv(), but not for writev().
> 
> > But yes, we definitely should support writev().
> 
> I just get an EIO error and have not traced this down any further.

What arguments are you feeding to it?  Note that the thing is sensitive to
range boundaries; it's not as if series of write() to it would be equivalent
to single write() from concatenation.  And writev() is equivalent to
series of write().

If you want behaviour a-la UDP sockets (syscall boundaries matter,
boundaries between vector elements do not), we can certainly do that,
but this is different from the current semantics.  AFAICS, said
semantics makes little sense, but it's a user-visible change...

  reply	other threads:[~2015-03-12  6:34 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-08 22:24 efivarfs and writev() support Marcel Holtmann
2015-03-11 13:42 ` Matt Fleming
2015-03-11 15:12   ` Marcel Holtmann
2015-03-12  6:34     ` Al Viro [this message]
2015-03-12 14:58       ` Marcel Holtmann
2015-03-12 17:03         ` Al Viro
2015-03-14 16:33           ` Marcel Holtmann
2015-03-17 15:46             ` Matt Fleming
2015-03-17 16:03               ` Marcel Holtmann

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=20150312063437.GK29656@ZenIV.linux.org.uk \
    --to=viro@zeniv.linux.org.uk \
    --cc=jk@ozlabs.org \
    --cc=linux-efi@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marcel@holtmann.org \
    --cc=matt.fleming@intel.com \
    --cc=matt@codeblueprint.co.uk \
    --cc=matthew.garrett@nebula.com \
    /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).