linux-kernel - Re: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map

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Date:   Thu, 13 Jun 2019 09:48:16 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Andrei Vagin <avagin@...il.com>
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Michal Koutný <mkoutny@...e.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Roman Gushchin <guro@...com>, Dmitry Safonov <dima@...sta.com>
Subject: Re: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for
 /proc/pid/map_files

On Wed, Jun 12, 2019 at 04:14:28PM -0700, Andrei Vagin wrote:
> On Sun, Jun 09, 2019 at 01:09:00PM +0300, Konstantin Khlebnikov wrote:
> > Do not stuck forever if something wrong.
> > Killable lock allows to cleanup stuck tasks and simplifies investigation.
> 
> This patch breaks the CRIU project, because stat() returns EINTR instead
> of ENOENT:
> 
> [root@...4 criu]# stat /proc/self/map_files/0-0
> stat: cannot stat '/proc/self/map_files/0-0': Interrupted system call
> 
> Here is one inline comment with the fix for this issue.
> 
> > 
> > It seems ->d_revalidate() could return any error (except ECHILD) to
> > abort validation and pass error as result of lookup sequence.
> > 
> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> > Reviewed-by: Roman Gushchin <guro@...com>
> > Reviewed-by: Cyrill Gorcunov <gorcunov@...il.com>
> > Reviewed-by: Kirill Tkhai <ktkhai@...tuozzo.com>
> 
> It was nice to see all four of you in one place :).

Holymoly ;) And we all managed to miss this error code.
Thanks, Andrew!