Hello! I am seeing a strange phenomenon here that I have not been able to completely figure out and perhaps it might ring some bells for somebody else. I first noticed this in 4.6-rc testing in early June, but just hit it in a similar way in 4.8-rc5 Basically I have a test script that does a bunch of stuff in a limited namespace in three related namespaced (backend is the same, mountpoints are separate). When a process (a process group or something) is killed, sometimes ones of the mountpoints disappears from the namespace completely, even though the scripts themselves do not unmount anything. No traces of the mountpoint anywhere in /proc (including /proc/*/mounts), so it's not in any private namespaces of any of the processes either it seems. The filesystems are a locally mounted ext4 (loopback-backed) + 2 nfs (of the ext4 reexported). In the past it was always ext4 that was dropping, but today I got one of the nfs ones. Sequence looks like this: + mount /tmp/loop /mnt/lustre -o loop + mkdir /mnt/lustre/racer mkdir: cannot create directory '/mnt/lustre/racer': File exists + service nfs-server start Redirecting to /bin/systemctl start nfs-server.service + mount localhost:/mnt/lustre /mnt/nfs -t nfs -o nolock + mount localhost:/ /mnt/nfs2 -t nfs4 + DURATION=3600 + sh racer.sh /mnt/nfs/racer + DURATION=3600 + sh racer.sh /mnt/nfs2/racer + wait %1 %2 %3 + DURATION=3600 + sh racer.sh /mnt/lustre/racer Running racer.sh for 3600 seconds. CTRL-C to exit Running racer.sh for 3600 seconds. CTRL-C to exit Running racer.sh for 3600 seconds. CTRL-C to exit ./file_exec.sh: line 12: 216042 Bus error $DIR/$file 0.$((RANDOM % 5 + 1)) 2> /dev/null ./file_exec.sh: line 12: 229086 Segmentation fault (core dumped) $DIR/$file 0.$((RANDOM % 5 + 1)) 2> /dev/null ./file_exec.sh: line 12: 230134 Segmentation fault $DIR/$file 0.$((RANDOM % 5 + 1)) 2> /dev/null ./file_exec.sh: line 12: 235154 Segmentation fault (core dumped) $DIR/$file 0.$((RANDOM % 5 + 1)) 2> /dev/null ./file_exec.sh: line 12: 270951 Segmentation fault (core dumped) $DIR/$file 0.$((RANDOM % 5 + 1)) 2> /dev/null racer cleanup racer cleanup racer cleanup sleeping 5 sec ... sleeping 5 sec ... sleeping 5 sec ... file_create.sh: no process found file_create.sh: no process found dir_create.sh: no process found file_create.sh: no process found dir_create.sh: no process found file_rm.sh: no process found dir_create.sh: no process found file_rm.sh: no process found file_rename.sh: no process found file_rm.sh: no process found file_rename.sh: no process found file_link.sh: no process found file_rename.sh: no process found file_link.sh: no process found file_symlink.sh: no process found file_link.sh: no process found file_symlink.sh: no process found file_list.sh: no process found file_list.sh: no process found file_symlink.sh: no process found file_concat.sh: no process found file_concat.sh: no process found file_list.sh: no process found file_exec.sh: no process found file_concat.sh: no process found file_exec.sh: no process found file_chown.sh: no process found file_exec.sh: no process found file_chown.sh: no process found file_chmod.sh: no process found file_chown.sh: no process found file_chmod.sh: no process found file_mknod.sh: no process found file_chmod.sh: no process found file_mknod.sh: no process found file_truncate.sh: no process found file_mknod.sh: no process found file_delxattr.sh: no process found file_truncate.sh: no process found file_truncate.sh: no process found file_getxattr.sh: no process found file_delxattr.sh: no process found file_delxattr.sh: no process found file_setxattr.sh: no process found there should be NO racer processes: file_getxattr.sh: no process found file_getxattr.sh: no process found file_setxattr.sh: no process found there should be NO racer processes: file_setxattr.sh: no process found there should be NO racer processes: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND df: /mnt/nfs/racer: No such file or directory Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop0 999320 46376 884132 5% /mnt/lustre We survived racer.sh for 3600 seconds. Filesystem 1K-blocks Used Available Use% Mounted on localhost:/ 999424 46080 884224 5% /mnt/nfs2 We survived racer.sh for 3600 seconds. + umount /mnt/nfs umount: /mnt/nfs: not mounted + exit 5 Now you see in the middle of that /mnt/nfs suddenly disappeared. The racer scripts are at http://git.whamcloud.com/fs/lustre-release.git/tree/refs/heads/master:/lustre/tests/racer There's absolutely no unmounts in there. In the past I was just able to do the three racers in parallel, wait ~10 minutes and then kill all three of them and with significant probability the ext4 mountpoint would disappear. Any idea on how to better pinpoint this? Thanks. Bye, Oleg-- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
