On Tue, 23 May 2006, Neil Brown wrote:

I've spent all morning looking at this and while I cannot see what is
happening I did find a couple of small bugs, so that is good...

I've attached three patches.  The first fix two small bugs (I think).
The last adds some extra information to
  /sys/block/mdX/md/stripe_cache_active

They are against 2.6.16.11.

If you could apply them and if the problem recurs, report the content
of stripe_cache_active several times before and after changing it,
just like you did last time, that might help throw some light on the
situation.

i applied them against 2.6.16.18 and two days later i got my first hang... 
below is the stripe_cache foo.

thanks
-dean

neemlark:~# cd /sys/block/md4/md/
neemlark:/sys/block/md4/md# cat stripe_cache_active 
255
0 preread
bitlist=0 delaylist=255
neemlark:/sys/block/md4/md# cat stripe_cache_active 
255
0 preread
bitlist=0 delaylist=255
neemlark:/sys/block/md4/md# cat stripe_cache_active 
255
0 preread
bitlist=0 delaylist=255
neemlark:/sys/block/md4/md# cat stripe_cache_active 
255
0 preread
bitlist=0 delaylist=255
neemlark:/sys/block/md4/md# cat stripe_cache_active 
255
0 preread
bitlist=0 delaylist=255
neemlark:/sys/block/md4/md# cat stripe_cache_size 
256
neemlark:/sys/block/md4/md# echo 512 >stripe_cache_size
neemlark:/sys/block/md4/md# cat stripe_cache_active
474
187 preread
bitlist=0 delaylist=222
neemlark:/sys/block/md4/md# cat stripe_cache_active
438
222 preread
bitlist=0 delaylist=72
neemlark:/sys/block/md4/md# cat stripe_cache_active
438
222 preread
bitlist=0 delaylist=72
neemlark:/sys/block/md4/md# cat stripe_cache_active
469
222 preread
bitlist=0 delaylist=72
neemlark:/sys/block/md4/md# cat stripe_cache_active
512
72 preread
bitlist=160 delaylist=103
neemlark:/sys/block/md4/md# cat stripe_cache_active
1
0 preread
bitlist=0 delaylist=0
neemlark:/sys/block/md4/md# cat stripe_cache_active
2
0 preread
bitlist=0 delaylist=0
neemlark:/sys/block/md4/md# cat stripe_cache_active
0
0 preread
bitlist=0 delaylist=0
neemlark:/sys/block/md4/md# cat stripe_cache_active
2
0 preread
bitlist=0 delaylist=0
neemlark:/sys/block/md4/md# 

md4 : active raid5 sdd1[0] sde1[5](S) sdh1[4] sdg1[3] sdf1[2] sdc1[1]
      1562834944 blocks level 5, 128k chunk, algorithm 2 [5/5] [UUUUU]
      bitmap: 10/187 pages [40KB], 1024KB chunk