From: Andrew Morton <akpm@linux-foundation.org>
To: Miklos Szeredi <mszeredi@suse.cz>
Cc: Jan Kara <jack@suse.cz>,
linux-mm@kvack.org, Al Viro <viro@ZenIV.linux.org.uk>,
Jay <jinshan.xiong@whamcloud.com>,
stable@kernel.org, Nick Piggin <npiggin@kernel.dk>
Subject: Re: [PATCH] mm: Fix assertion mapping->nrpages == 0 in end_writeback()
Date: Tue, 7 Jun 2011 14:33:01 -0700 [thread overview]
Message-ID: <20110607143301.7dbaf146.akpm@linux-foundation.org> (raw)
In-Reply-To: <1307425597.3649.61.camel@tucsk.pomaz.szeredi.hu>
On Tue, 07 Jun 2011 07:46:37 +0200
Miklos Szeredi <mszeredi@suse.cz> wrote:
> > Either way, I don't think that the uglypatch expresses a full
> > understanding of te bug ;)
>
> I don't see a better way, how would we make nrpages update atomically
> wrt the radix-tree while using only RCU?
>
> The question is, does it matter that those two can get temporarily out
> of sync?
>
> In case of inode eviction it does, not only because of that BUG_ON, but
> because page reclaim must be somehow synchronised with eviction.
> Otherwise it may access tree_lock on the mapping of an already freed
> inode.
>
> In other cases? AFAICS it doesn't matter. Most ->nrpages accesses
> weren't under tree_lock before Nick's RCUification, so their use were
> just optimization.
Gee, we've made a bit of a mess here.
Rather than bodging around particualr codesites where that mess exposes
itself, how about we step back and work out what our design is here,
then implement it and check that all sites comply with it?
What is the relationship between the radix-tree and nrpages? What are
the locking rules? Can anyone come up with a one-sentence proposal?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-06-07 21:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-30 9:37 [PATCH] mm: Fix assertion mapping->nrpages == 0 in end_writeback() Jan Kara
2011-06-06 22:16 ` Andrew Morton
2011-06-07 5:46 ` Miklos Szeredi
2011-06-07 18:22 ` Jinshan Xiong
2011-06-08 16:40 ` Jan Kara
2011-06-08 20:10 ` Jinshan Xiong
2011-06-07 21:33 ` Andrew Morton [this message]
2011-06-08 16:36 ` Jan Kara
2011-06-13 22:01 ` Jan Kara
2011-06-13 22:14 ` Andrew Morton
2011-06-13 22:49 ` Jan Kara
2011-06-13 22:58 ` Andrew Morton
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=20110607143301.7dbaf146.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=jack@suse.cz \
--cc=jinshan.xiong@whamcloud.com \
--cc=linux-mm@kvack.org \
--cc=mszeredi@suse.cz \
--cc=npiggin@kernel.dk \
--cc=stable@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).