Re: next/mmotm: ext4 causes !rwsem_is_locked warnings

On Thu, Sep 27, 2012 at 02:05:00PM -0700, Hugh Dickins wrote:

Hi Ted,

mmotm (or next) now gives me lots of WARNING at fs/fs-writeback.c:1312 from
writeback_inodes_sb_nr().  That's WARN_ON(!rwsem_is_locked(&sb->s_umount))
(some useful safety from hch) in writeback_inodes_sb_nr().

Your commit 40e684e5c597a98996cf4616e31fb2581ec82060
"ext4: fix potential deadlock in ext4_nonda_switch()" needs more change
to fs/fs-writeback.c.  I guess I'm the only one using a nearly full ext4.

I am, of course, applying the patch at the bottom to my tree for now;
but I think you'd do better not to eliminate that check.  Maybe add a
special wb_reason for your case, and skip rwsem check in that case.

Yeah, we were just discussing this on another thread.  I didn't think
of the option of creating a new special wb_reason option, but that's a
much better option than the other ones I had been considering, so I
think I will give that a try.   Thanks for the suggestion!!

      	     	       	 	       - Ted