From: Ian Kent <raven@themaw.net>
To: Fox Chen <foxhlchen@gmail.com>
Cc: akpm@linux-foundation.org, dhowells@redhat.com,
gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, miklos@szeredi.hu,
ricklind@linux.vnet.ibm.com, sfr@canb.auug.org.au, tj@kernel.org,
viro@ZenIV.linux.org.uk
Subject: Re: [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement
Date: Sun, 13 Dec 2020 11:46:13 +0800 [thread overview]
Message-ID: <bde0b6c32f2b055c1ad1401b45c4adf61aab6876.camel@themaw.net> (raw)
In-Reply-To: <13e21e4c9a5841243c8d130cf9324f6cfc4dc2e1.camel@themaw.net>
On Fri, 2020-12-11 at 10:17 +0800, Ian Kent wrote:
> On Fri, 2020-12-11 at 10:01 +0800, Ian Kent wrote:
> > > For the patches, there is a mutex_lock in kn->attr_mutex, as
> > > Tejun
> > > mentioned here
> > > (https://lore.kernel.org/lkml/X8fe0cmu+aq1gi7O@mtj.duckdns.org/),
> > > maybe a global
> > > rwsem for kn->iattr will be better??
> >
> > I wasn't sure about that, IIRC a spin lock could be used around the
> > initial check and checked again at the end which would probably
> > have
> > been much faster but much less conservative and a bit more ugly so
> > I just went the conservative path since there was so much change
> > already.
>
> Sorry, I hadn't looked at Tejun's reply yet and TBH didn't remember
> it.
>
> Based on what Tejun said it sounds like that needs work.
Those attribute handling patches were meant to allow taking the rw
sem read lock instead of the write lock for kernfs_refresh_inode()
updates, with the added locking to protect the inode attributes
update since it's called from the VFS both with and without the
inode lock.
Looking around it looks like kernfs_iattrs() is called from multiple
places without a node database lock at all.
I'm thinking that, to keep my proposed change straight forward
and on topic, I should just leave kernfs_refresh_inode() taking
the node db write lock for now and consider the attributes handling
as a separate change. Once that's done we could reconsider what's
needed to use the node db read lock in kernfs_refresh_inode().
It will reduce the effectiveness of the series but it would make
this change much more complicated, and is somewhat off-topic, and
could hamper the chances of reviewers spotting problem with it.
Ian
next prev parent reply other threads:[~2020-12-13 3:47 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-17 7:37 [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Ian Kent
2020-06-17 7:37 ` [PATCH v2 1/6] kernfs: switch kernfs to use an rwsem Ian Kent
2020-06-17 7:37 ` [PATCH v2 2/6] kernfs: move revalidate to be near lookup Ian Kent
2020-06-17 7:37 ` [PATCH v2 3/6] kernfs: improve kernfs path resolution Ian Kent
2020-06-17 7:38 ` [PATCH v2 4/6] kernfs: use revision to identify directory node changes Ian Kent
2020-06-17 7:38 ` [PATCH v2 5/6] kernfs: refactor attr locking Ian Kent
2020-06-17 7:38 ` [PATCH v2 6/6] kernfs: make attr_mutex a local kernfs node lock Ian Kent
2020-06-19 15:38 ` [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Tejun Heo
2020-06-19 20:41 ` Rick Lindsley
2020-06-19 22:23 ` Tejun Heo
2020-06-20 2:44 ` Rick Lindsley
2020-06-22 17:53 ` Tejun Heo
2020-06-22 21:22 ` Rick Lindsley
2020-06-23 23:13 ` Tejun Heo
2020-06-24 9:04 ` Rick Lindsley
2020-06-24 9:27 ` Greg Kroah-Hartman
2020-06-24 13:19 ` Tejun Heo
2020-06-25 8:15 ` Ian Kent
2020-06-25 9:43 ` Greg Kroah-Hartman
2020-06-26 0:19 ` Ian Kent
2020-06-21 4:55 ` Ian Kent
2020-06-22 17:48 ` Tejun Heo
2020-06-22 18:03 ` Greg Kroah-Hartman
2020-06-22 21:27 ` Rick Lindsley
2020-06-23 5:21 ` Greg Kroah-Hartman
2020-06-23 5:09 ` Ian Kent
2020-06-23 6:02 ` Greg Kroah-Hartman
2020-06-23 8:01 ` Ian Kent
2020-06-23 8:29 ` Ian Kent
2020-06-23 11:49 ` Greg Kroah-Hartman
2020-06-23 9:33 ` Rick Lindsley
2020-06-23 11:45 ` Greg Kroah-Hartman
2020-06-23 22:55 ` Rick Lindsley
2020-06-23 11:51 ` Ian Kent
2020-06-21 3:21 ` Ian Kent
2020-12-10 16:44 ` Fox Chen
2020-12-11 2:01 ` [PATCH " Ian Kent
2020-12-11 2:17 ` Ian Kent
2020-12-13 3:46 ` Ian Kent [this message]
2020-12-14 6:14 ` Fox Chen
2020-12-14 13:30 ` Ian Kent
2020-12-15 8:33 ` Fox Chen
2020-12-15 12:59 ` Ian Kent
2020-12-17 4:46 ` Ian Kent
2020-12-17 8:54 ` Fox Chen
2020-12-17 10:09 ` Ian Kent
2020-12-17 11:09 ` Ian Kent
2020-12-17 11:48 ` Ian Kent
2020-12-17 15:14 ` Tejun Heo
2020-12-18 7:36 ` Ian Kent
2020-12-18 8:01 ` Fox Chen
2020-12-18 11:21 ` Ian Kent
2020-12-18 13:20 ` Fox Chen
2020-12-19 0:53 ` Ian Kent
2020-12-19 7:47 ` Fox Chen
2020-12-22 2:17 ` Ian Kent
2020-12-18 14:59 ` Tejun Heo
2020-12-19 7:08 ` Ian Kent
2020-12-19 16:23 ` Tejun Heo
2020-12-19 23:52 ` Ian Kent
2020-12-20 1:37 ` Ian Kent
2020-12-21 9:28 ` Fox Chen
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=bde0b6c32f2b055c1ad1401b45c4adf61aab6876.camel@themaw.net \
--to=raven@themaw.net \
--cc=akpm@linux-foundation.org \
--cc=dhowells@redhat.com \
--cc=foxhlchen@gmail.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=ricklind@linux.vnet.ibm.com \
--cc=sfr@canb.auug.org.au \
--cc=tj@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).