linux-ext4 - Re: [REPORT] syscall reboot + umh + firmware fallback

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220523011045.GA16721@X58A-UD3R>
Date:   Mon, 23 May 2022 10:10:45 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     tj@...nel.org, torvalds@...ux-foundation.org,
        damien.lemoal@...nsource.wdc.com, linux-ide@...r.kernel.org,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        mingo@...hat.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, will@...nel.org, tglx@...utronix.de,
        rostedt@...dmis.org, joel@...lfernandes.org, sashal@...nel.org,
        daniel.vetter@...ll.ch, chris@...is-wilson.co.uk,
        duyuyang@...il.com, johannes.berg@...el.com, willy@...radead.org,
        david@...morbit.com, amir73il@...il.com,
        gregkh@...uxfoundation.org, kernel-team@....com,
        linux-mm@...ck.org, akpm@...ux-foundation.org, mhocko@...nel.org,
        minchan@...nel.org, hannes@...xchg.org, vdavydov.dev@...il.com,
        sj@...nel.org, jglisse@...hat.com, dennis@...nel.org, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, vbabka@...e.cz,
        ngupta@...are.org, linux-block@...r.kernel.org,
        paolo.valente@...aro.org, josef@...icpanda.com,
        linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
        jack@...e.cz, jack@...e.com, jlayton@...nel.org,
        dan.j.williams@...el.com, hch@...radead.org, djwong@...nel.org,
        dri-devel@...ts.freedesktop.org, rodrigosiqueiramelo@...il.com,
        melissa.srw@...il.com, hamohammed.sa@...il.com,
        42.hyeyoo@...il.com, mcgrof@...nel.org, holt@....com
Subject: Re: [REPORT] syscall reboot + umh + firmware fallback

On Thu, May 12, 2022 at 09:56:46AM -0400, Theodore Ts'o wrote:
> On Thu, May 12, 2022 at 08:18:24PM +0900, Byungchul Park wrote:
> > I have a question about this one. Yes, it would never been stuck thanks
> > to timeout. However, IIUC, timeouts are not supposed to expire in normal
> > cases. So I thought a timeout expiration means not a normal case so need
> > to inform it in terms of dependency so as to prevent further expiraton.
> > That's why I have been trying to track even timeout'ed APIs.
> 
> As I beleive I've already pointed out to you previously in ext4 and
> ocfs2, the jbd2 timeout every five seconds happens **all** the time
> while the file system is mounted.  Commits more frequently than five
> seconds is the exception case, at least for desktops/laptop workloads.

Thanks, Ted. It's easy to stop tracking APIs with timeout. I've been
just afraid that the cases that we want to suppress anyway will be
skipped.

However, I should stop it if it produces too many false alarms.

> We *don't* get to the timeout only when a userspace process calls
> fsync(2), or if the journal was incorrectly sized by the system
> administrator so that it's too small, and the workload has so many
> file system mutations that we have to prematurely close the
> transaction ahead of the 5 second timeout.

Yeah... It's how journaling works. Thanks.

> > Do you think DEPT shouldn't track timeout APIs? If I was wrong, I
> > shouldn't track the timeout APIs any more.
> 
> DEPT tracking timeouts will cause false positives in at least some
> cases.  At the very least, there needs to be an easy way to suppress
> these false positives on a per wait/mutex/spinlock basis.

The easy way is to stop tracking those that are along with timeout until
DEPT starts to consider waits/events by timeout functionality itself.

Thanks.

	Byungchul
> 
>       	       	    	     	      	   	 - Ted