BUG 795642 - remount -o remount,ro doesn't leave FS consistent

[pv@xxxxxxxxxxxxx (dxm@xxxxxxxxxxxx)]

View Incident: 
http://co-op.engr.sgi.com/BugWorks/code/bwxquery.cgi?search=Search&wlong=1&view_type=Bug&wi=795642

Submitter : dxm                       Submitter Domain : engr               
Assigned Engineer : btg               Assigned Domain : sgi.com             
Assigned Group : xfs-linux            Category : software                   
Customer Reported : F                 Priority : 3                          
Project : xfs-linux                   Status : open                         
Description :
Remounting an XFS filesystem R/O can leave the FS in an
inconsistent state. (Playing with this for long enough can
hang mount up...)

Reproduce with QA 013 or:

#!/bin/sh

DEV=/dev/hda6
MNT=/mnt/arch0

umount $DEV &> /dev/null 
mkfs -t xfs -f $DEV &> /dev/null || exit 1

mount -t xfs $DEV $MNT || exit 1
for l in 0 1 2 3 4 5 6 7 8 9
do
        fsstress -n 100 -d $MNT 
        mount -o remount,ro $DEV
        if ! xfs_check $DEV &> /dev/null 
        then
                echo "FAIL"
                exit 1
        fi
        mount -o remount,rw $DEV
done

compare with ext2 behaviour:

#!/bin/sh

DEV=/dev/hda8
MNT=/mnt/arch1

umount $DEV &> /dev/null 
mkfs $DEV &> /dev/null || exit 1

mount $DEV $MNT || exit 1
for l in 0 1 2 3 4 5 6 7 8 9
do
        fsstress -n 100 -d $MNT 
        mount -o remount,ro $DEV
        if ! xfs_check $DEV &> /dev/null 
        then
                echo "FAIL"
                exit 1
        fi
        mount -o remount,rw $DEV
done