Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount completion

From	Jaegeuk Kim <jaegeuk@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount completion
Date	2017-09-21 19:20 +0200
Message-ID	<usdiQ-3Se-73@gated-at.bofh.it> (permalink)
References	(2 earlier) <urS4G-6Jl-17@gated-at.bofh.it> <urXH5-1Ui-49@gated-at.bofh.it> <urZIS-3fm-7@gated-at.bofh.it> <us1Ul-4Rt-1@gated-at.bofh.it> <usb7k-2jN-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 09/21, Theodore Ts'o wrote:
> On Wed, Sep 20, 2017 at 10:02:37PM -0700, Jaegeuk Kim wrote:
> > 
> > Yes, and actually, android retries umount(2) for several seconds, if it gets
> > failure. So, first I thought it'd be better to make umount() more deterministic.
> > 
> > I'm not sure how many times we can retry and wait for this. IMHO, it'd be better
> > to use this together with the new flag, since this can detect unclosed namespace
> > given successful umount(2).
> 
> Even if you could make umount wait for the binder deferred workqueue
> to exit, if it takes time, it takes time.  And that's not the core
> VFS's fault.  It's binder's.
> 
> So... why not fix this by adding a binder ioctl which forces its
> workqueue to be flushed, and use that *before* you try calling mount?

Yes, we can, but I'm not 100% sure this happens only by binder. This is caused
by delayed_fput/mntput called by any kernel thread which would be much generic.

> If that binder ioctl takes minutes or hours to complete, then that's a
> binder bug, and needs to be fixed in binder.
> 
>        	    	      	    	  - Ted

Thread

[PATCH] vfs: introduce UMOUNT_WAIT which waits for umount completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-13 22:20 +0200
  Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-14 01:10 +0200
    Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-14 01:40 +0200
      Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-14 01:50 +0200
        Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-14 03:20 +0200
          Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-14 03:40 +0200
            Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-14 20:40 +0200
              Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-14 21:20 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-15 02:20 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-15 04:10 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-15 05:50 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-15 06:30 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-15 20:50 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Theodore Ts'o <tytso@mit.edu> - 2017-09-16 00:20 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-16 01:30 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-16 01:50 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-19 18:00 +0200
                Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount completion Amir Goldstein <amir73il@gmail.com> - 2017-09-16 09:20 +0200
  Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-20 19:40 +0200
    Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-20 20:40 +0200
      Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-21 02:40 +0200
        Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-21 04:50 +0200
          Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-21 07:10 +0200
            Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Theodore Ts'o <tytso@mit.edu> - 2017-09-21 17:00 +0200
              Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount  completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-21 19:20 +0200
    Re: [PATCH v3] vfs: introduce UMOUNT_WAIT to wait for  delayed_fput/mntput completion Jaegeuk Kim <jaegeuk@kernel.org> - 2017-09-21 20:30 +0200

csiph-web