Re: [PATCH block/for-linus] writeback: flush inode cgroup wb switches instead of pinning super_block

From	Jan Kara <jack@suse.cz>
Newsgroups	linux.kernel
Subject	Re: [PATCH block/for-linus] writeback: flush inode cgroup wb switches instead of pinning super_block
Date	2016-02-29 22:30 +0100
Message-ID	<r7Dya-8nS-17@gated-at.bofh.it> (permalink)
References	(5 earlier) <r7CVr-7Vn-1@gated-at.bofh.it> <r7D58-7Z4-13@gated-at.bofh.it> <r7D59-7Z4-25@gated-at.bofh.it> <r7DeO-8hr-31@gated-at.bofh.it> <r7DeO-8hr-29@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon 29-02-16 16:08:00, Tejun Heo wrote:
> On Mon, Feb 29, 2016 at 09:06:15PM +0000, Al Viro wrote:
> > > Hmmm?  The flushing is done after shrink_dcache_for_umount() and
> > > sync_filesystems().  Aren't inodes supposed to stay clean after that?
> > 
> > s/shrink_dcache_for_umount/fsnotify_unmount_inodes/ - sorry.
> 
> Is that allowed to dirty indoes and initiate writebacks again, after
> sync_filesystems() is done?  That sounds weird but it's trivial to
> move cgroup_writeback_umount() below that if so.

Hardly, but generally it is true that filesystem may still dirty something
(e.g. from outstanding workqueue work, but most likely some special "system
inodes" may still become dirty) until ->put_super() is finished.

Anyway, to make this foolproof, I'd just avoid queueing any new switching
work after S_ACTIVE is cleared on the superblock and flush the workqueue just
before evict_inodes() call.

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

Thread

[PATCH block/for-linus] writeback: flush inode cgroup wb switches  instead of pinning super_block Tejun Heo <tj@kernel.org> - 2016-02-29 21:50 +0100
  Re: [PATCH block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Al Viro <viro@ZenIV.linux.org.uk> - 2016-02-29 22:00 +0100
    Re: [PATCH block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Tejun Heo <tj@kernel.org> - 2016-02-29 22:00 +0100
      Re: [PATCH block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Tejun Heo <tj@kernel.org> - 2016-02-29 22:10 +0100
        Re: [PATCH block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Jan Kara <jack@suse.cz> - 2016-02-29 22:30 +0100
      Re: [PATCH block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Al Viro <viro@ZenIV.linux.org.uk> - 2016-02-29 22:10 +0100
  [PATCH v2 block/for-linus] writeback: flush inode cgroup wb switches  instead of pinning super_block Tejun Heo <tj@kernel.org> - 2016-03-01 00:30 +0100
    Re: [PATCH v2 block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Jan Kara <jack@suse.cz> - 2016-03-01 10:30 +0100
    Re: [PATCH v2 block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Jens Axboe <axboe@kernel.dk> - 2016-03-01 18:50 +0100
      Re: [PATCH v2 block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Tejun Heo <tj@kernel.org> - 2016-03-01 19:00 +0100
        Re: [PATCH v2 block/for-linus] writeback: flush inode cgroup wb  switches instead of pinning super_block Jan Kara <jack@suse.cz> - 2016-03-02 11:30 +0100
  Re: [PATCH block/for-linus] writeback: flush inode cgroup wb switches  instead of pinning super_block Tahsin Erdogan <tahsin@google.com> - 2016-03-01 14:40 +0100

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