Re: review: fix remount vs barrier options

[Timothy Shimmin <tes@sgi.com>]

Nathan Scott wrote:
> Hi,
> 
> Jeremy has had me scratching my head for a few days trying to
> figure out how the SCSI traces he's looking at can still show
> signs of write barriers being issued to the device, despite a
> "remount,nobarrier" having been done.
> 
> It finally clicked that we are not clearing the buffer flag
> from a previously written log buffer, even though we'll no
> longer set a new flag into a buffer (due to the mount flag
> being cleared), so we _can_ still issue barrier writes when
> remounted without barriers.
> 
> This was made more complicated by the way a freshly mounted
> filesystem with 8 log buffers wouldn't show up the problem,
> since we have to slowly cycle through the "clear" log buffers
> before we see the bug.  This seems like the simplest fix...
> 
> (Hmmm, actually, I wonder if this will also resolve the quota
> log I/O problem that was reported the other day too).
> 
Patch looks good to me.

--Tim