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Bug 1244257

Summary: alloc: Fix lvextend failure when varying stripes.
Product: Red Hat Enterprise Linux 6 Reporter: George Angelopoulos <gangelop>
Component: lvm2Assignee: Alasdair Kergon <agk>
lvm2 sub component: Striping (RHEL6) QA Contact: cluster-qe <cluster-qe>
Status: CLOSED ERRATA Docs Contact:
Severity: high    
Priority: high CC: agk, heinzm, jbrassow, jherrman, msnitzer, nperic, prajnoha, prockai, rbednar, tlavigne, zkabelac
Version: 6.8Keywords: ZStream
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Linux   
Whiteboard:
Fixed In Version: lvm2-2.02.140-1.el6 Doc Type: Bug Fix
Doc Text:
When extending a logical volume (LV) where the amount of data stripes was previously lowered, the LV terminated unexpectedly with a segmentation fault due to an error in stripe position detection. With this update, the behavior of a number of functions related to stripe detection has been adjusted to prevent the bug, and the described crash no longer occurs.
 Story Points: ---
Clone Of:
: 1248051 (view as bug list) Environment:
Last Closed: 2016-05-11 01:17:57 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1248051, 1268411    

Description George Angelopoulos 2015-07-17 15:16:57 UTC 
Description of problem:

A segfault was reported when extending an LV with a smaller number of
stripes than originally used.  Under unusual circumstances, the cling
detection code could successfully find a match against the excess
stripe positions and think it had finished prematurely leading to an
allocation being pursued with a length of zero.

Rename ix_offset to num_positional_areas and move it to struct
alloc_state so that _is_condition() can obtain access to it.


Version-Release number of selected component (if applicable):
lvm2-2.02.87-6.el6.x86_64
lvm2-libs-2.02.87-6.el6.x86_64


How reproducible:
Hasn't been reproduced.


Additional info:

Upstream submitted patch
https://lists.fedorahosted.org/pipermail/lvm2-commits/2015-July/004304.html
Comment 2 Alasdair Kergon 2015-07-20 16:16:59 UTC 
Problematic layout reported:

seg1 - start 0 - 4 stripes - len 4 x 65536 = 262144
/pv_manip.c:415         pv0 2: start  65536 len 65536: lvol0(0:0)
/pv_manip.c:415         pv0 4: start 196608 len 65536: lvol0(0:1)
/pv_manip.c:415         pv1 3: start 131712 len 65536: lvol0(0:2)
/pv_manip.c:415         pv1 0: start      0 len 65536: lvol0(0:3)

seg2 - start 262144 - 4 stripes - len 4 x 65536 = 262144
/pv_manip.c:415         pv0 3: start 131072 len 65536: lvol0(262144:0)
/pv_manip.c:415         pv0 5: start 262144 len 65536: lvol0(262144:1)
/pv_manip.c:415         pv1 4: start 197248 len 65536: lvol0(262144:2)
/pv_manip.c:415         pv1 2: start  66176 len 65536: lvol0(262144:3)

seg3 - start 524288 - 2 stripes - len 2 x 640 = 1280
/pv_manip.c:415         pv0 0: start     0 len   640: lvol0(524288:0)
/pv_manip.c:415         pv1 1: start 65536 len   640: lvol0(524288:1)

Unallocated space:
/pv_manip.c:415         pv0 1: start    640 len  64896: NULL(0:0)
/pv_manip.c:415         pv0 6: start 327680 len 101054: NULL(0:0)
/pv_manip.c:415         pv1 5: start 262784 len 165950: NULL(0:0)

followed by lvextend -i2
Comment 3 Nenad Peric 2015-07-29 13:34:26 UTC 
In order to try and verify this issue, one should create a striped LV of width 4 (i 4), in Comment #2 it is of 32MiB, and then extend by 2 stripes. (-i2)
Comment 5 Peter Rajnoha 2015-08-03 09:41:58 UTC 
To QA:

The easiest way to reproduce this issue and check the fix is to use the layout that customer had exactly - you can use thin volumes to simulate the exact dev size customer had (the underlying device for testing can be really small - mine is 128MiB, but even smaller will do the job - we're not writing much into thin volumes representing PVs, so we hardly run out of real space here):

# pvcreate /dev/sda
  Physical volume "/dev/sda" successfully created

# vgcreate vg /dev/sda
  Volume group "vg" successfully created

# lvcreate -l100%FREE -T vg/pool
  Logical volume "pool" created.

# lvcreate -V 1714940m -T vg/pool -n pv0
  Logical volume "pv0" created.

# lvcreate -V 1714940m -T vg/pool -n pv1
  Logical volume "pv1" created.

# pvcreate --restorefile vgbackup -u 68K1Yf-geMe-fAZK-TUF1-dRvq-w4Zo-vf08jc /dev/vg/pv0
  Couldn't find device with uuid 68K1Yf-geMe-fAZK-TUF1-dRvq-w4Zo-vf08jc.
  Couldn't find device with uuid lPcNxu-9fAE-M3Pe-hzCM-SJLk-wQ37-lYsq84.
  Physical volume "/dev/vg/pv0" successfully created

# pvcreate --restorefile vgbackup -u lPcNxu-9fAE-M3Pe-hzCM-SJLk-wQ37-lYsq84 /dev/vg/pv1
  Couldn't find device with uuid lPcNxu-9fAE-M3Pe-hzCM-SJLk-wQ37-lYsq84.
  Physical volume "/dev/vg/pv1" successfully created

# vgcfgrestore -f vgbackup vgbackup
  Restored volume group vgbackup

# lvextend -L +1G -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
  Size of logical volume vgbackup/backor_pool changed from 2.00 TiB (524288 extents) to 2.00 TiB (524544 extents).
  Logical volume backor_pool successfully resized

# lvextend -l +100%FREE -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
Segmentation fault (core dumped)

(the last step should pass correctly without segfault in the version where this issue is fixed)
Comment 7 Nenad Peric 2015-08-03 11:06:54 UTC 
Before patch:

[root@virt-007 backup]# lvextend -l +100%FREE -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
Segmentation fault (core dumped)


After patch (126-1):

[root@virt-007 ~]# lvextend -l +100%FREE -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
  Size of logical volume vgbackup/backor_pool changed from 2.00 TiB (524544 extents) to 3.27 TiB (857468 extents).
  Logical volume backor_pool successfully resized


This fix was VERIFIED with:

lvm2-2.02.126-1.el7.x86_64
Comment 10 Roman Bednář 2016-02-15 12:31:31 UTC 
VERIFIED

Before patch:

[root@virt-012 backup]# lvextend -l +100%FREE -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
Segmentation fault (core dumped)


After patch:

[root@virt-010 backup]# lvextend -l +100%FREE -i 2 /dev/vgbackup/backor_pool
  Using stripesize of last segment 128.00 KiB
  Size of logical volume vgbackup/backor_pool changed from 2.00 TiB (524544 extents) to 3.27 TiB (857468 extents).
  Logical volume backor_pool successfully resized.


Tested on:

2.6.32-614.el6.x86_64

lvm2-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
lvm2-libs-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
lvm2-cluster-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
udev-147-2.71.el6    BUILT: Wed Feb 10 14:07:17 CET 2016
device-mapper-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-libs-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-event-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-event-libs-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-persistent-data-0.6.2-0.1.rc1.el6    BUILT: Wed Feb 10 16:52:15 CET 2016
cmirror-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
Comment 12 errata-xmlrpc 2016-05-11 01:17:57 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-0964.html