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ad4eec6135
It's always been a hassle that if an external journal's
device number changes, the filesystem won't mount.
And since boot-time enumeration can change, device number
changes aren't unusual.
The current mechanism to update the journal location is by
passing in a mount option w/ a new devnum, but that's a hassle;
it's a manual approach, fixing things after the fact.
Adding a mount option, "-o journal_path=/dev/$DEVICE" would
help, since then we can do i.e.
# mount -o journal_path=/dev/disk/by-label/$JOURNAL_LABEL ...
and it'll mount even if the devnum has changed, as shown here:
# losetup /dev/loop0 journalfile
# mke2fs -L mylabel-journal -O journal_dev /dev/loop0
# mkfs.ext4 -L mylabel -J device=/dev/loop0 /dev/sdb1
Change the journal device number:
# losetup -d /dev/loop0
# losetup /dev/loop1 journalfile
And today it will fail:
# mount /dev/sdb1 /mnt/test
mount: wrong fs type, bad option, bad superblock on /dev/sdb1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
# dmesg | tail -n 1
[17343.240702] EXT4-fs (sdb1): error: couldn't read superblock of external journal
But with this new mount option, we can specify the new path:
# mount -o journal_path=/dev/loop1 /dev/sdb1 /mnt/test
#
(which does update the encoded device number, incidentally):
# umount /dev/sdb1
# dumpe2fs -h /dev/sdb1 | grep "Journal device"
dumpe2fs 1.41.12 (17-May-2010)
Journal device: 0x0701
But best of all we can just always mount by journal-path, and
it'll always work:
# mount -o journal_path=/dev/disk/by-label/mylabel-journal /dev/sdb1 /mnt/test
#
So the journal_path option can be specified in fstab, and as long as
the disk is available somewhere, and findable by label (or by UUID),
we can mount.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
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| .. | ||
| caching | ||
| configfs | ||
| nfs | ||
| pohmelfs | ||
| 9p.txt | ||
| 00-INDEX | ||
| adfs.txt | ||
| affs.txt | ||
| afs.txt | ||
| autofs4-mount-control.txt | ||
| automount-support.txt | ||
| befs.txt | ||
| bfs.txt | ||
| btrfs.txt | ||
| ceph.txt | ||
| cifs.txt | ||
| coda.txt | ||
| cramfs.txt | ||
| debugfs.txt | ||
| devpts.txt | ||
| directory-locking | ||
| dlmfs.txt | ||
| dnotify_test.c | ||
| dnotify.txt | ||
| ecryptfs.txt | ||
| efivarfs.txt | ||
| exofs.txt | ||
| ext2.txt | ||
| ext3.txt | ||
| ext4.txt | ||
| f2fs.txt | ||
| fiemap.txt | ||
| files.txt | ||
| fuse.txt | ||
| gfs2-glocks.txt | ||
| gfs2-uevents.txt | ||
| gfs2.txt | ||
| hfs.txt | ||
| hfsplus.txt | ||
| hpfs.txt | ||
| inotify.txt | ||
| isofs.txt | ||
| jfs.txt | ||
| Locking | ||
| locks.txt | ||
| logfs.txt | ||
| Makefile | ||
| mandatory-locking.txt | ||
| ncpfs.txt | ||
| nilfs2.txt | ||
| ntfs.txt | ||
| ocfs2.txt | ||
| omfs.txt | ||
| path-lookup.txt | ||
| porting | ||
| proc.txt | ||
| qnx6.txt | ||
| quota.txt | ||
| ramfs-rootfs-initramfs.txt | ||
| relay.txt | ||
| romfs.txt | ||
| seq_file.txt | ||
| sharedsubtree.txt | ||
| spufs.txt | ||
| squashfs.txt | ||
| sysfs-pci.txt | ||
| sysfs-tagging.txt | ||
| sysfs.txt | ||
| sysv-fs.txt | ||
| tmpfs.txt | ||
| ubifs.txt | ||
| udf.txt | ||
| ufs.txt | ||
| vfat.txt | ||
| vfs.txt | ||
| xfs-delayed-logging-design.txt | ||
| xfs-self-describing-metadata.txt | ||
| xfs.txt | ||
| xip.txt | ||