[5.4-p6] Trouble with swap_pager: indefinite wait buffer on LSI(PERC4)-RAID on Dell PE6650

[Raphael H. Becker]

Hi *,

one of our Dell PE6650 (4x Xeon, HTT, 2GB RAM) crash from time to time
with kernel messages like:

swap_pager: indefinite wait buffer: device amrd1s1d, blkno 77 

Any access to the RAID is impossible (e.g. login on console, shutdown,
... ), have to powercycle it.

What is the meaning of this message? 
What is the causation for this error? 
Does swap_pager crash the RAID? Maybe under load? Maybe any locking/SMP?

swap seems to work: Swap: 2048M Total, 144K Used, 2048M Free

Some technical details:

* This filesystem is pretty loaded/stressed by the webserver/CMS and
  periodic rsync-jobs.

Filesystem       Size    Used   Avail Capacity iused    ifree %iused Mounted on
/dev/amrd1s1d    265G     77G    167G    32% 1415076 34454618    4% /data

* There is a 2GB swap on amrd0s2b (or what is the problem with swap_pager?)

* From dmesg:
amr0: <LSILogic MegaRAID 1.51> mem 0xfce00000-0xfce0ffff irq 21 at device 1.0 on pci3
amr0: <LSILogic PERC 4/DC> Firmware 351S, BIOS 1.10, 128MB RAM
amrd0: <LSILogic MegaRAID logical drive> on amr0
amrd0: 69880MB (143114240 sectors) RAID 1 (optimal)
amrd1: <LSILogic MegaRAID logical drive> on amr0
amrd1: 279800MB (573030400 sectors) RAID 5 (optimal)

* from pciconf:
amr0 at pci3:1:0:  class=0x010400 card=0x05181028 chip=0x19601000 rev=0x01 hdr=0x00
    vendor   = 'LSI Logic (Was: Symbios Logic, NCR)'
    class    = mass storage
    subclass = RAID

* a typical load average is "1.02,  1.05,  1.05" (actually 52 httpd
  processes, have seen up to 120 httpd)

* Kernel is 5.4-RELEASE-p6 with GENERIC plus SMP
include GENERIC
ident PE6650
options SMP

Is there anything I can do?
Any switches? sysctl?
Is 6.0-RELEASE or will 6.1-RELEASE be a solution for that?
Any patches in 5-STABLE?


Need more info?

Need more testing? I have a second machine of this which acts as a
standby/fallback-system. I may test some things here (without workload).

TIA

Regards
Raphael Becker