Bug 1303815

Summary: RAID device mount point show as 'rw' after it remounted as 'ro' by EXT4-fs
Product: Red Hat Enterprise Linux 6 Reporter: Zhang Yi <yizhan>
Component: util-linux-ngAssignee: Karel Zak <kzak>
Status: CLOSED WONTFIX QA Contact: qe-baseos-daemons
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.8CC: esandeen, fs-qe, lczerner
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-02-02 09:51:01 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:

Description Zhang Yi 2016-02-02 05:06:56 UTC 
Description of problem:
RAID device mount point show as 'rw' after it remounted as 'ro' by EXT4-fs

Version-Release number of selected component (if applicable):
# rpm -qf /bin/mount
util-linux-ng-2.17.2-12.20.el6.x86_64

# uname -r
2.6.32-591.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Create raid5 with four disks
#mdadm -CR /dev/md0 -l5 -n4 /dev/sd[bcde]1
2. mkfs.ext4 and mount the /dev/md0
#mkfs.ext4 /dev/md0 && mount /dev/md0 /mnt
3. do dd write operation on the mount point background
#dd if=/dev/urandom of=/mnt/testfile bs=4096 &
4. set two device faulty.
#mdadm /dev/md0 -f /dev/sdb1
#mdadm /dev/md0 -f /dev/sdc1
5. check the dmesg and mount point info

Actual results:
mount point show as 'rw'

Expected results:
show as 'ro'

Additional info:
# mount | grep md0
/dev/md0 on /mnt type ext4 (rw)

# cat /proc/mounts | grep md
/dev/md0 /mnt ext4 ro,seclabel,relatime,barrier=1,stripe=512,data=ordered 0 0


dmesg:
EXT4-fs (md0): mounted filesystem with ordered data mode. Opts: 
md/raid:md0: Disk failure on sdb1, disabling device.
md/raid:md0: Operation continuing on 4 devices.
md/raid:md0: Disk failure on sdc1, disabling device.
md/raid:md0: Operation continuing on 3 devices.
Buffer I/O error on device md0, logical block 917138
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917266
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917394
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917010
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917139
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917267
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917395
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917011
lost page write due to I/O error on md0
Buffer I/O error on device md0, logical block 917140
lost page write due to I/O error on md0
JBD2: Detected IO errors while flushing file data on md0-8
Aborting journal on device md0-8.
EXT4-fs (md0): ext4_da_writepages: jbd2_start: 8192 pages, ino 12; err -30

EXT4-fs (md0): ext4_da_writepages: jbd2_start: 8192 pages, ino 12; err -30

EXT4-fs (md0): ext4_da_writepages: jbd2_start: 1024 pages, ino 12; err -30

JBD2: I/O error detected when updating journal superblock for md0-8.
EXT4-fs error (device md0): ext4_journal_start_sb: Detected aborted journal
EXT4-fs (md0): Remounting filesystem read-only
EXT4-fs (md0): ext4_da_writepages: jbd2_start: 8192 pages, ino 12; err -30

JBD2: Detected IO errors while flushing file data on md0-8
Comment 2 Karel Zak 2016-02-02 09:51:01 UTC 
man mount, section BUGS:

It  is  possible  that files /etc/mtab and /proc/mounts don't match. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g.  remote NFS server. In particular case the mount command may reports unreliable information...)


... this is something we cannot fix in RHEL6. This is reason why we does not have mtab in the >= RHEL7.