[Linux-cachefs] Overlong wait for old active object to go away

[Mark Hills]

I find CacheFiles gives a valuable performance benefit, but unfortunately 
is not usable due to hangs.

In dmesg "Overlong wait for old active object to go away" (see full 
message below), and an application will hang or lock, eg. blocking on 
read().

Sometimes it unblocks, sometimes it seems to hang indefinitely. Is there a 
higher level explanation for what is going on here?

It seems logical that the message is a symptom, rather than the cause 
itself. What could hold the lock in such a way?

The timeout in question appears to be "60 * HZ" in fs/cachefiles/namei.c. 
I am using the default configuration of cachefilesd, from Git, and kernel 
2.6.39.4.

Many thanks,

-- 
Mark


CacheFiles: Error: Overlong wait for old active object to go away
object: OBJb2
objstate=OBJECT_LOOKING_UP fl=0 wbusy=2 ev=0[7b]
ops=0 inp=0 exc=0
parent=ffff8802253da280
cookie=ffff8801bb25e500 [pr=ffff880226993000 nd=ffff880215f38c60 fl=7]
key=[28] '010006015cd1795b8c9f417c8beaffe8b6b51c531e36cc0a7a2a6a96'
xobject: OBJ1a
xobjstate=OBJECT_RECYCLING fl=0 wbusy=2 ev=20[3]
xops=0 inp=0 exc=0
xparent=ffff8802253da280
xcookie=NULL