Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1337350

Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned during cgroup writeback association switches

Show all headers | View raw

Hi Tejun,

On Thu 18-02-16 08:00:33, Tejun Heo wrote:
> On Thu, Feb 18, 2016 at 10:55:38AM +0100, Jan Kara wrote:
> > I'm not sure I understand the question. Do you mean why both s_active and
> > s_umount rwsem exist? s_active is a reference count keeping superblock
> 
> Yes.
> 
> > alive - e.g. if the filesystem is mounted in more places, we need a
> > reference for each mountpoint. s_umount is used when we want to block any
> 
> I could be mistaken but I *think* we used to reject umounts based on
> s_active and s_umount is the mechanism to delay umounts rather than
> failing them and probably with bind mounts the behavior changed.
> 
> > umount operation until we are done. For example sync(2) is using it to make
> > sure superblock doesn't disappear and so that we don't keep superblock
> > alive after admin called umount(2).
> 
> So, the question is why aren't we just using s_active and draining it
> on umount of the last mountpoint.  Because, right now, the behavior is
> weird in that we allow umounts to proceed but then let the superblock
> hang onto the block device till s_active is drained.  This really
> should be synchronous.

Hum, I'm not sure. I guess Al can give you more qualified answer than me.
Added to CC...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH block/for-4.5-fixes] writeback: keep superblock pinned during  cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-16 19:30 +0100
  Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Jens Axboe <axboe@kernel.dk> - 2016-02-16 19:40 +0100
  Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Jan Kara <jack@suse.cz> - 2016-02-17 22:00 +0100
    Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-17 22:10 +0100
      Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Jan Kara <jack@suse.cz> - 2016-02-17 23:30 +0100
        Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tahsin Erdogan <tahsin@google.com> - 2016-02-17 23:50 +0100
          Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-18 00:10 +0100
            Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Jan Kara <jack@suse.cz> - 2016-02-18 11:00 +0100
              Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-18 14:10 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Jan Kara <jack@suse.cz> - 2016-02-18 14:30 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Al Viro <viro@ZenIV.linux.org.uk> - 2016-02-19 21:20 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-19 22:00 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Al Viro <viro@ZenIV.linux.org.uk> - 2016-02-19 23:00 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-19 23:20 +0100
                Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Al Viro <viro@ZenIV.linux.org.uk> - 2016-02-19 23:30 +0100
  Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Nikolay Borisov <kernel@kyup.com> - 2016-02-18 11:20 +0100
    Re: [PATCH block/for-4.5-fixes] writeback: keep superblock pinned  during cgroup writeback association switches Tejun Heo <tj@kernel.org> - 2016-02-18 14:00 +0100

csiph-web