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Re: [git pull] vfs.git - including i_mutex wrappers

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On Sun, Jan 24, 2016 at 09:34:56AM +1100, Dave Chinner wrote:
> On Sat, Jan 23, 2016 at 02:58:54PM +0000, Al Viro wrote:
> > 	->i_mutex wrappers (with small prereq in lustre), fix for too
> 
> Please explain, Al?
> 
> I haven't heard anything about there being i_mutex changes pending,
> and this commit says "over the coming cycle ->i_mutex will become
> rwsem".  That's a complete surprise to me, and not something that
> should be done with no warning.
> 
> What's the locking model? How are filesystems supposed to use it?
> Are they even allowed to use read-mode locking, and if so, what
> operations is it going to be safe to hold the lock in read mode?
> 
> Why is this change considered valid now, when previously there's
> always been significant push-back to any suggestion that we should
> make the i_mutex a rwsem so we can do shared read-only access
> locking on inode operations?

FWIW, I'm not opposed to making such a locking change - I'm more
concerned about the fact I'm finding out about plans for such a
fundamental locking change from a pull request on the last day of a
merge window....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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[git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-23 16:00 +0100
  Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-23 23:40 +0100
    Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-23 23:50 +0100
      Re: [git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-24 00:20 +0100
        Re: [git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-24 00:40 +0100
        Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-24 02:00 +0100
          Re: [git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-24 02:50 +0100
            Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-24 08:10 +0100
              Re: [git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-24 08:50 +0100
      Re: [git pull] vfs.git - including i_mutex wrappers Linus Torvalds <torvalds@linux-foundation.org> - 2016-01-24 00:50 +0100
        Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-24 01:30 +0100
          Re: [git pull] vfs.git - including i_mutex wrappers Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-24 02:30 +0100
            Re: [git pull] vfs.git - including i_mutex wrappers Dave Chinner <david@fromorbit.com> - 2016-01-24 08:20 +0100

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