From: Christoph Hellwig <hch@infradead.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
"Oliver O'Halloran" <oohall@gmail.com>,
Yumei Huang <yuhuang@redhat.com>, Michal Hocko <mhocko@suse.com>,
Xiao Guangrong <guangrong.xiao@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
KVM list <kvm@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
Gleb Natapov <gleb@kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
mtosatti@redhat.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)
Date: Tue, 13 Sep 2016 00:17:32 -0700 [thread overview]
Message-ID: <20160913071732.GA19433@infradead.org> (raw)
In-Reply-To: <20160913115311.509101b0@roar.ozlabs.ibm.com>
On Tue, Sep 13, 2016 at 11:53:11AM +1000, Nicholas Piggin wrote:
> - Application mmaps a file, faults in block 0
> - FS allocates block, creates mappings, syncs metadata, sets "no fsync"
> flag for that block, and completes the fault.
> - Application writes some data to block 0, completes userspace flushes
>
> * At this point, a crash must return with above data (or newer).
>
> - Application starts writing more stuff into block 0
> - Concurrently, fault in block 1
> - FS starts to allocate, splits trees including mappings to block 0
>
> * Crash
>
> Is that right? How does your filesystem lose data before the sync
> point?
Witht all current file systems chances are your metadata hasn't been
flushed out. You could write all metadata synchronously from the
page fault handler, but that's basically asking for all kinds of
deadlocks.
> If there is any huge complexity or unsolved problem, it is in XFS.
> Conceptual problem is simple.
Good to have you back and make all the hard thing simple :)
next prev parent reply other threads:[~2016-09-13 7:17 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-08 4:32 DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams
2016-09-08 22:56 ` Ross Zwisler
2016-09-08 23:04 ` Dan Williams
2016-09-09 8:55 ` Xiao Guangrong
2016-09-09 15:40 ` Dan Williams
2016-09-12 6:00 ` Xiao Guangrong
2016-09-12 3:44 ` Rudoff, Andy
2016-09-12 6:31 ` Xiao Guangrong
2016-09-12 1:40 ` Dave Chinner
2016-09-15 5:55 ` Darrick J. Wong
2016-09-15 6:25 ` Dave Chinner
2016-09-12 5:27 ` Christoph Hellwig
2016-09-12 7:25 ` Oliver O'Halloran
2016-09-12 7:51 ` Christoph Hellwig
2016-09-12 8:05 ` Nicholas Piggin
2016-09-12 15:01 ` Christoph Hellwig
2016-09-13 1:31 ` Nicholas Piggin
2016-09-13 4:06 ` Dan Williams
2016-09-13 5:40 ` Nicholas Piggin
2016-09-12 21:34 ` Dave Chinner
2016-09-13 1:53 ` Nicholas Piggin
2016-09-13 7:17 ` Christoph Hellwig [this message]
2016-09-13 9:06 ` Nicholas Piggin
2016-09-14 7:39 ` Dave Chinner
2016-09-14 10:19 ` Nicholas Piggin
2016-09-15 2:31 ` Dave Chinner
2016-09-15 3:49 ` Nicholas Piggin
2016-09-15 10:32 ` Dave Chinner
2016-09-15 11:42 ` Nicholas Piggin
2016-09-15 22:33 ` Dave Chinner
2016-09-16 5:54 ` Nicholas Piggin
2016-12-19 21:11 ` Ross Zwisler
2016-12-20 1:09 ` Darrick J. Wong
2016-12-20 1:18 ` Dan Williams
2016-12-21 0:40 ` Darrick J. Wong
2016-12-21 16:53 ` Dan Williams
2016-12-21 21:24 ` Dave Chinner
2016-12-21 21:33 ` Dan Williams
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=20160913071732.GA19433@infradead.org \
--to=hch@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=dave.hansen@intel.com \
--cc=david@fromorbit.com \
--cc=gleb@kernel.org \
--cc=guangrong.xiao@linux.intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nvdimm@ml01.01.org \
--cc=mhocko@suse.com \
--cc=mtosatti@redhat.com \
--cc=npiggin@gmail.com \
--cc=oohall@gmail.com \
--cc=pbonzini@redhat.com \
--cc=stefanha@redhat.com \
--cc=yuhuang@redhat.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).