Bug 103711

Summary: Null pointer dereference in md raid 5 on get_free_stripe
Product: IO/Storage Reporter: e-kernel
Component: MDAssignee: io_md
Status: NEW ---    
Severity: high CC: gjunk2, neilb, szg00000
Priority: P1    
Hardware: x86-64   
OS: Linux   
Kernel Version: 4.1.6-1-ARCH Subsystem:
Regression: No Bisected commit-id:
Attachments: kernel crash trace
Kernel Log
ver_linux output
lspci -vvv output
/proc/iomem
/proc/ioreports
/proc/scsi/scsi

Description e-kernel 2015-08-29 14:40:20 UTC
Created attachment 186171 [details]
kernel crash trace

My file server just crashed with the attached kernel trace.
Running arch linux with kernel 4.1.6.

Raid configuration:
Personalities : [raid6] [raid5] [raid4] 
md127 : active raid5 sdd1[2] sdc1[4] sda1[1] sdb1[0]
      5860147200 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      bitmap: 0/15 pages [0KB], 65536KB chunk

Hardware:
4x2TB hard drives
Intel(R) Atom(TM) CPU  C2550  @ 2.40GHz
8GB ECC UDIMM
Comment 1 Gene 2015-09-03 01:23:03 UTC
I have the same problem. Takes quite a while to get this to happen. Typically 1 - 2 weeks of uptime. Best I can tell it crashes when the nightly backups are running and writing to the raid6 array.

Same kernel - 4.1.6 - details attached.

cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid6 sdf1[4] sdc1[1] sdh1[5] sde1[3] sdd1[2] sdb1[0]
      11720536064 blocks super 1.2 level 6, 512k chunk, algorithm 2 [6/6] [UUUUUU]
      bitmap: 0/22 pages [0KB], 65536KB chunk

unused devices: <none>
Comment 2 Gene 2015-09-03 01:23:49 UTC
Created attachment 186531 [details]
Kernel Log
Comment 3 Gene 2015-09-03 01:25:08 UTC
Created attachment 186541 [details]
ver_linux output
Comment 4 Gene 2015-09-03 01:25:46 UTC
Created attachment 186551 [details]
lspci -vvv output
Comment 5 Gene 2015-09-03 01:26:50 UTC
Created attachment 186561 [details]
/proc/iomem
Comment 6 Gene 2015-09-03 01:27:08 UTC
Created attachment 186571 [details]
/proc/ioreports
Comment 7 Gene 2015-09-03 01:27:52 UTC
Created attachment 186581 [details]
/proc/scsi/scsi
Comment 8 Neil Brown 2015-09-03 05:14:29 UTC
Fix by commit 
49895bcc7e566ba455eb2996607d6fbd3447ce16

should get into 4.1-stable eventually.
Comment 9 Gene 2015-09-03 12:35:10 UTC
Thanks Neil - assume this is in 4.2 already.