Re: Uneccesary flushes waking up suspended disks

["Theodore Ts'o" <tytso@mit.edu>]

On Fri, Mar 08, 2024 at 03:54:40PM -0500, Phillip Susi wrote:
> "Theodore Ts'o" <tytso@mit.edu> writes:
> 
> > Another fix would be making sure that the kernel isues the file system
> > syncs, and waits for them to be completed, *before* we freeze the
> > disk.  That way, if there are any dirty pages, they can be flushed to
> > stable store so that if the battery runs down while the laptop is
> > suspended, the user won't see data loss.
> 
> That's exactly how it works now.  The kernel syncs the fs before
> suspending, but during that sync, even though there were no dirty pages
> and so nothing has been written to the disk and it has been runtime
> suspended, the fs issues a flush, which wakes the disk up, only to be
> put right back to sleep so the system can transition to S3.

In an earlier message from you upthread, you had stated "Since the
disk is suspended however, there is nothing in the cache to flush, so
this is wasteful."  So that sounded like the flush was happening at
the wrong time, after the disk has already been suspended?

Am I missing something?

Thanks,

					- Ted