From: "Michael K. Edwards" <medwards.linux@gmail.com>
To: "Eric Dumazet" <dada1@cosmosbay.com>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: sys_write() racy for multi-threaded append?
Date: Thu, 8 Mar 2007 16:45:41 -0800 [thread overview]
Message-ID: <f2b55d220703081645vc78905cj56afbc58ad2113d8@mail.gmail.com> (raw)
In-Reply-To: <45F0A71C.2000800@cosmosbay.com>
On 3/8/07, Eric Dumazet <dada1@cosmosbay.com> wrote:
> Absolutely not. We dont want to slow down kernel 'just in case a fool might
> want to do crazy things'
Actually, I think it would make the kernel (negligibly) faster to bump
f_pos before the vfs_write() call. Unless fget_light sets fput_needed
or the write doesn't complete cleanly, you won't have to touch the
file table entry again after vfs_write() returns. You can adjust
vfs_write to grab f_dentry out of the file before going into
do_sync_write. do_sync_write is done with the struct file before it
goes into the aio_write() loop. Result: you probably save at least an
L1 cache miss, unless the aio_write loop is so frugal with L1 cache
that it doesn't manage to evict the struct file.
Patch to follow.
Cheers,
- Michael
next prev parent reply other threads:[~2007-03-09 0:45 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-08 23:08 sys_write() racy for multi-threaded append? Michael K. Edwards
2007-03-08 23:43 ` Eric Dumazet
2007-03-08 23:57 ` Michael K. Edwards
2007-03-09 0:15 ` Eric Dumazet
2007-03-09 0:45 ` Michael K. Edwards [this message]
2007-03-09 1:34 ` Benjamin LaHaise
2007-03-09 12:19 ` Michael K. Edwards
2007-03-09 13:44 ` Eric Dumazet
2007-03-09 14:10 ` Alan Cox
2007-03-09 14:59 ` Benjamin LaHaise
2007-03-10 6:43 ` Michael K. Edwards
2007-03-09 5:53 ` Eric Dumazet
2007-03-09 11:52 ` Michael K. Edwards
2007-03-09 0:43 ` Alan Cox
[not found] <7WzUo-1zl-21@gated-at.bofh.it>
[not found] ` <7WAx2-2pg-21@gated-at.bofh.it>
[not found] ` <7WAGF-2Bx-9@gated-at.bofh.it>
[not found] ` <7WB07-3g5-33@gated-at.bofh.it>
[not found] ` <7WBt7-3SZ-23@gated-at.bofh.it>
2007-03-12 7:53 ` Bodo Eggert
2007-03-12 16:26 ` Michael K. Edwards
2007-03-12 18:48 ` Bodo Eggert
2007-03-13 0:46 ` Michael K. Edwards
2007-03-13 2:24 ` Alan Cox
2007-03-13 7:25 ` Michael K. Edwards
2007-03-13 7:42 ` David Miller
2007-03-13 16:24 ` Michael K. Edwards
2007-03-13 17:59 ` Michael K. Edwards
2007-03-13 19:09 ` Christoph Hellwig
2007-03-13 23:40 ` Michael K. Edwards
2007-03-14 0:09 ` Michael K. Edwards
2007-03-13 13:15 ` Alan Cox
2007-03-14 20:09 ` Michael K. Edwards
2007-03-16 16:43 ` Frank Ch. Eigler
2007-03-16 17:25 ` Alan Cox
2007-03-13 14:00 ` David M. Lloyd
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=f2b55d220703081645vc78905cj56afbc58ad2113d8@mail.gmail.com \
--to=medwards.linux@gmail.com \
--cc=dada1@cosmosbay.com \
--cc=linux-kernel@vger.kernel.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 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).