From: Suparna Bhattacharya <suparna@in.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: daniel@osdl.org, janetmor@us.ibm.com, pbadari@us.ibm.com,
linux-aio@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH linux-2.6.1-rc1-mm1] aiodio_fallback_bio_count.patch
Date: Mon, 5 Jan 2004 10:58:46 +0530 [thread overview]
Message-ID: <20040105052846.GA3810@in.ibm.com> (raw)
In-Reply-To: <20040104210642.2b94038f.akpm@osdl.org>
On Sun, Jan 04, 2004 at 09:06:42PM -0800, Andrew Morton wrote:
> Suparna Bhattacharya <suparna@in.ibm.com> wrote:
> >
> > > What is the significance of `written > count' in there, and of `dio->result
> > > > dio->size' in finished_one_bio()? How can these states come about?
> > >
> >
> > Both of these are checks to determine whether all or only a part of
> > the request was serviced by DIO, leaving the rest to be serviced by
> > falling back to buffered I/O.
> >
> > Earlier, we would decide this based on whether dio->result == -ENOTBLK
> > and written == -ENOTBLK respectively. However, now that we also need the
> > result to indicate how much actually got written even in -ENOTBLK case,
> > so that we can issue buffered i/o only for the remaining part of the request,
> > dio->result and written had to be modified to reflect the number of bytes
> > transferred by DIO even for the fallback to buffered i/o case.
> > So we need checks like this to find out whether there is some i/o left
> > to be issued via buffered i/o.
>
> Sure. But the generic_file_aio_write_nolock() code is doing this:
>
> if (written >= count && !is_sync_kiocb(iocb))
> written = -EIOCBQUEUED;
> if (written < 0 || written >= count)
> goto out_status;
>
>
> Under what circumstances can `written' (the amount which was written) be
> greater than `count' (the amount to write)?
None. The '>' situation should never occur.
This is just being explicit about covering the "not less than" case
as a whole, and making sure we do not fall through to buffered i/o in
that case, i.e its the same as:
if (!(written < count) && !is_sync_kiocb(iocb))
Is that any less confusing ? Or would you rather just replace the '>=" by
"=='.
Regards
Suparna
--
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India
next prev parent reply other threads:[~2004-01-05 5:23 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3FCD4B66.8090905@us.ibm.com>
2003-12-06 1:29 ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Daniel McNeil
2003-12-08 18:23 ` Daniel McNeil
2003-12-12 0:51 ` Daniel McNeil
2003-12-17 1:25 ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Daniel McNeil
2003-12-17 2:03 ` Andrew Morton
2003-12-17 19:25 ` Daniel McNeil
2003-12-17 20:17 ` Janet Morgan
2003-12-31 9:18 ` Suparna Bhattacharya
2003-12-31 9:35 ` Andrew Morton
2003-12-31 9:55 ` Suparna Bhattacharya
2003-12-31 9:59 ` Andrew Morton
2003-12-31 10:09 ` Suparna Bhattacharya
2003-12-31 10:10 ` Andrew Morton
2003-12-31 10:48 ` Suparna Bhattacharya
2003-12-31 10:53 ` Andrew Morton
2003-12-31 10:54 ` Andrew Morton
2003-12-31 11:17 ` Andrew Morton
2003-12-31 22:34 ` [PATCH linux-2.6.1-rc1-mm1] filemap_fdatawait.patch Daniel McNeil
2003-12-31 22:41 ` [PATCH linux-2.6.1-rc1-mm1] aiodio_fallback_bio_count.patch Daniel McNeil
2003-12-31 23:46 ` Andrew Morton
2004-01-02 5:14 ` Suparna Bhattacharya
2004-01-02 7:46 ` Andrew Morton
2004-01-05 3:55 ` Suparna Bhattacharya
2004-01-05 5:06 ` Andrew Morton
2004-01-05 5:28 ` Suparna Bhattacharya [this message]
2004-01-05 5:28 ` Andrew Morton
2004-01-05 6:06 ` Suparna Bhattacharya
2004-01-05 6:14 ` Lincoln Dale
2003-12-31 22:47 ` [PATCH linux-2.6.1-rc1-mm1] dio_isize.patch Daniel McNeil
2003-12-31 23:42 ` [PATCH linux-2.6.1-rc1-mm1] filemap_fdatawait.patch Andrew Morton
2004-01-02 4:20 ` Suparna Bhattacharya
2004-01-02 4:36 ` Andrew Morton
2004-01-02 5:50 ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Suparna Bhattacharya
2004-01-02 7:31 ` Andrew Morton
2004-01-05 13:49 ` Marcelo Tosatti
2004-01-05 20:27 ` Andrew Morton
2004-03-29 15:44 ` Marcelo Tosatti
2004-01-11 23:14 ` Janet Morgan
2004-01-11 23:44 ` Andrew Morton
2004-01-12 18:00 ` filemap_fdatawait.patch Daniel McNeil
2004-01-12 19:39 ` [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch Janet Morgan
2004-01-12 19:46 ` Daniel McNeil
2004-01-13 4:12 ` Janet Morgan
2003-12-30 4:53 ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Suparna Bhattacharya
2003-12-31 0:29 ` Daniel McNeil
2003-12-31 6:09 ` Suparna Bhattacharya
2004-01-08 23:55 ` Daniel McNeil
2004-01-09 3:55 ` Suparna Bhattacharya
2004-02-05 1:39 ` [PATCH 2.6.2-rc3-mm1] DIO read race fix Daniel McNeil
2004-02-05 1:54 ` Badari Pulavarty
2004-02-05 2:07 ` Andrew Morton
2004-02-05 2:54 ` Janet Morgan
2004-02-05 3:19 ` Andrew Morton
2004-02-05 3:43 ` Suparna Bhattacharya
2004-02-05 5:33 ` Andrew Morton
2004-02-05 17:52 ` Daniel McNeil
2004-02-05 18:53 ` Badari Pulavarty
2004-03-29 15:41 ` [PATCH linux-2.6.0-test10-mm1] dio-read-race-fix Suparna Bhattacharya
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=20040105052846.GA3810@in.ibm.com \
--to=suparna@in.ibm.com \
--cc=akpm@osdl.org \
--cc=daniel@osdl.org \
--cc=janetmor@us.ibm.com \
--cc=linux-aio@kvack.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbadari@us.ibm.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).