Re: [PATCH 1/1] suspend: delete sys_sync()

On Wednesday, July 08, 2015 10:40:00 AM Alan Stern wrote:

On Wed, 8 Jul 2015, Pavel Machek wrote:

quoted

quoted

well, that depends on what the purpose of the sync is supposed to be.

If it is there to prevent users from corrupting their filesystems as a result
of a mistake, it is insufficient.  If it's there for other reasons, I'm wondering
what those reasons are (on systems that suspend and resume reliably, because the
original reason to put it in there was to reduce the damage from suspend/resume
crashes).

I put it there, and there were more reasons than "crashes" to put it
there.

1) crashes.

2) battery is quite likely to run out in suspended machine.

3) if someone pulls the stick and puts it in other machine, I wanted
consistent filesystem at least after journal replay.

I was going to make the same points.

From my point of view, whether to issue a sync is a tradeoff.  I can't
remember any time in the last several years where lack of a sync would
have caused a problem for my computers, but the possibility still
exists.

So on one hand, issuing the sync can help prevent a low-probability 
problem.  On the other hand, issuing the sync takes a small amount of 
time (negligible for my purposes but not negligible for Len and 
others).

I prefer to pay a very small cost to prevent a low-probability problem.  
Others may not want to pay, because to them the cost is larger or the 
probability is lower.

_That_ is the justification for not eliminating the sync completely but 
making it optional.

Agreed.

Thanks,
Rafael