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

From Theodore Ts'o <tytso@mit.edu>
Newsgroups linux.kernel
Subject Re: [PATCH v2] vfs: introduce UMOUNT_WAIT which waits for umount completion
Date 2017-09-21 17:00 +0200
Message-ID <usb7k-2jN-17@gated-at.bofh.it> (permalink)
References (1 earlier) <urR8D-67N-31@gated-at.bofh.it> <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>
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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?

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

       	    	      	    	  - Ted

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[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

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