Date: Tue, 19 Sep 2017 11:33:18 +0200 From: Andreas Longwitz <longwitz@incore.de> To: freebsd-fs@freebsd.org Subject: nullfs with double mount is broken in FreeBSD 10 Stable Message-ID: <59C0E45E.3070603@incore.de>
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The described problem does not exist in V8, but in V10 Stable r317936. I use a device /dev/md2 defined in /etc/rc.conf: mdconfig_md2="-t swap -s 384m" mdconfig_md2_newfs="-n" mdconfig_md2_owner="root:wheel" mdconfig_md2_perms="750" In /etc/fstab I have: /dev/md2 /tmp1 ufs rw,async,noatime,noauto 0 0 /tmp1 /home/tmp1 nullfs rw,noauto 0 0 /tmp1 /var/tmp1 nullfs rw,noauto 0 0 Now I run: mount /home/tmp1 mount /var/tmp1 while true; do rm -f /home/tmp1/* cpdup /boot/kernel /home/tmp1 cp /var/tmp1/kernel /dev/null df -h /tmp1 done The output is Filesystem Size Used Avail Capacity Mounted on /dev/md2 372M 88M 254M 26% /tmp1 Filesystem Size Used Avail Capacity Mounted on /dev/md2 372M 100M 242M 29% /tmp1 Filesystem Size Used Avail Capacity Mounted on /dev/md2 372M 112M 229M 33% /tmp1 Filesystem Size Used Avail Capacity Mounted on /dev/md2 372M 125M 217M 36% /tmp1 ..... The "Used" space grows quickly until "No space available". After umount /var/tmp1 the space is back again. I see the same behaviour when md is replaced by tmpfs. I have tried the patch from commit 317936 (V11) without success. The problem exists on i386 and amd64. In production (V8) I use this double mount construction for jail communication without any problems. -- Andreas Longwitz
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