On Fri, Sep 9, 2016 at 11:56 AM, Kent Overstreet 
[off-list ref] wrote:

On Wed, Sep 07, 2016 at 01:12:12PM -0800, Kent Overstreet wrote:

quoted

 So, right now we're checking i_nlinks on every mount - mainly the 
dirents
 implementation predates the transactional machinery we have now. 
That's almost
 definitely what's taking so long, but I'll send you a patch to 
confirm later.

I just pushed a patch to add printks for the various stages of 
recovery: use
mount -o verbose_recovery to enable.

How many files does this filesystem have? (df -i will tell you).

As another data point, on my laptop mounting takes half a second - 
smallish
filesystem though, 47 gb of data and 711k inodes (and it's on an 
SSD). My
expectation is that mount times with the current code will be good 
enough as
long as you're using SSDs (or tiering, where tier 0 is SSD) - but I 
could use
more data points.

FWIW, I've got a tier 0 SSD in front of two 3TB HDDs, 1.8M inodes and 
150GB used, and that takes 380ms to mount if systemd-analyse is to be 
trusted.