ext4: allow specifying external journal by pathname mount option
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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@ -144,11 +144,12 @@ journal_async_commit Commit block can be written to disk without waiting
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mount the device. This will enable 'journal_checksum'
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internally.
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journal_path=path
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journal_dev=devnum When the external journal device's major/minor numbers
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have changed, this option allows the user to specify
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have changed, these options allow the user to specify
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the new journal location. The journal device is
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identified through its new major/minor numbers encoded
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in devnum.
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identified through either its new major/minor numbers
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encoded in devnum, or via a path to the device.
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norecovery Don't load the journal on mounting. Note that
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noload if the filesystem was not unmounted cleanly,
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@ -1134,8 +1134,8 @@ enum {
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Opt_nouid32, Opt_debug, Opt_removed,
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Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
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Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload,
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Opt_commit, Opt_min_batch_time, Opt_max_batch_time,
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Opt_journal_dev, Opt_journal_checksum, Opt_journal_async_commit,
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Opt_commit, Opt_min_batch_time, Opt_max_batch_time, Opt_journal_dev,
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Opt_journal_path, Opt_journal_checksum, Opt_journal_async_commit,
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Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
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Opt_data_err_abort, Opt_data_err_ignore,
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Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
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@ -1179,6 +1179,7 @@ static const match_table_t tokens = {
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{Opt_min_batch_time, "min_batch_time=%u"},
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{Opt_max_batch_time, "max_batch_time=%u"},
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{Opt_journal_dev, "journal_dev=%u"},
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{Opt_journal_path, "journal_path=%s"},
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{Opt_journal_checksum, "journal_checksum"},
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{Opt_journal_async_commit, "journal_async_commit"},
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{Opt_abort, "abort"},
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@ -1338,6 +1339,7 @@ static int clear_qf_name(struct super_block *sb, int qtype)
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#define MOPT_NO_EXT2 0x0100
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#define MOPT_NO_EXT3 0x0200
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#define MOPT_EXT4_ONLY (MOPT_NO_EXT2 | MOPT_NO_EXT3)
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#define MOPT_STRING 0x0400
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static const struct mount_opts {
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int token;
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@ -1387,6 +1389,7 @@ static const struct mount_opts {
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{Opt_resuid, 0, MOPT_GTE0},
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{Opt_resgid, 0, MOPT_GTE0},
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{Opt_journal_dev, 0, MOPT_GTE0},
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{Opt_journal_path, 0, MOPT_STRING},
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{Opt_journal_ioprio, 0, MOPT_GTE0},
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{Opt_data_journal, EXT4_MOUNT_JOURNAL_DATA, MOPT_NO_EXT2 | MOPT_DATAJ},
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{Opt_data_ordered, EXT4_MOUNT_ORDERED_DATA, MOPT_NO_EXT2 | MOPT_DATAJ},
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@ -1480,7 +1483,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
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return -1;
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}
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if (args->from && match_int(args, &arg))
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if (args->from && !(m->flags & MOPT_STRING) && match_int(args, &arg))
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return -1;
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if (args->from && (m->flags & MOPT_GTE0) && (arg < 0))
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return -1;
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@ -1544,6 +1547,44 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
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return -1;
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}
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*journal_devnum = arg;
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} else if (token == Opt_journal_path) {
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char *journal_path;
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struct inode *journal_inode;
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struct path path;
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int error;
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if (is_remount) {
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ext4_msg(sb, KERN_ERR,
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"Cannot specify journal on remount");
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return -1;
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}
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journal_path = match_strdup(&args[0]);
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if (!journal_path) {
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ext4_msg(sb, KERN_ERR, "error: could not dup "
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"journal device string");
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return -1;
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}
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error = kern_path(journal_path, LOOKUP_FOLLOW, &path);
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if (error) {
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ext4_msg(sb, KERN_ERR, "error: could not find "
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"journal device path: error %d", error);
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kfree(journal_path);
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return -1;
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}
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journal_inode = path.dentry->d_inode;
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if (!S_ISBLK(journal_inode->i_mode)) {
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ext4_msg(sb, KERN_ERR, "error: journal path %s "
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"is not a block device", journal_path);
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path_put(&path);
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kfree(journal_path);
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return -1;
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}
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*journal_devnum = new_encode_dev(journal_inode->i_rdev);
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path_put(&path);
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kfree(journal_path);
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} else if (token == Opt_journal_ioprio) {
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if (arg > 7) {
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ext4_msg(sb, KERN_ERR, "Invalid journal IO priority"
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