| Message ID | 51F83D90.5080708@redhat.com |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Tue 30-07-13 17:26:24, Eric Sandeen wrote: > 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 /mnt > > 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.ext3 -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] EXT3-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> > --- > > The patch is a little hacky, doing all the work in option parsing, > just to get to a journal devnum like the old option expected, only > to later re-decode it when we really want to open it. > > I could clean it up so that both journal-update mount options > find the bdev, rather than ending with an encoded device number, > which must then be decoded & re-opened, if that seems better. > > But this was expedient enough to get the idea out on the list. > > If we like it, I'll do ext4 as well. Yeah, it looks like a good idea. You could just lookup the path via kern_path() and then take the device numbers from the inode so you won't have to do the decode-recode dance. That would look like the cleanest option to me. Honza > diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt > index 293855e..7ed0d17 100644 > --- a/Documentation/filesystems/ext3.txt > +++ b/Documentation/filesystems/ext3.txt > @@ -26,11 +26,12 @@ journal=inum When a journal already exists, this option is ignored. > Otherwise, it specifies the number of the inode which > will represent the ext3 file system's journal file. > > +journal_path=path > journal_dev=devnum When the external journal device's major/minor numbers > - have changed, this option allows the user to specify > + have changed, these options allow the user to specify > the new journal location. The journal device is > - identified through its new major/minor numbers encoded > - in devnum. > + identified through either its new major/minor numbers > + encoded in devnum, or via a path to the device. > > norecovery Don't load the journal on mounting. Note that this forces > noload mount of inconsistent filesystem, which can lead to > diff --git a/fs/ext3/super.c b/fs/ext3/super.c > index c47f147..cb1dd6e 100644 > --- a/fs/ext3/super.c > +++ b/fs/ext3/super.c > @@ -819,6 +819,7 @@ enum { > Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl, > Opt_reservation, Opt_noreservation, Opt_noload, Opt_nobh, Opt_bh, > Opt_commit, Opt_journal_update, Opt_journal_inum, Opt_journal_dev, > + Opt_journal_path, > Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback, > Opt_data_err_abort, Opt_data_err_ignore, > Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota, > @@ -860,6 +861,7 @@ static const match_table_t tokens = { > {Opt_journal_update, "journal=update"}, > {Opt_journal_inum, "journal=%u"}, > {Opt_journal_dev, "journal_dev=%u"}, > + {Opt_journal_path, "journal_path=%s"}, > {Opt_abort, "abort"}, > {Opt_data_journal, "data=journal"}, > {Opt_data_ordered, "data=ordered"}, > @@ -975,6 +977,9 @@ static int parse_options (char *options, struct super_block *sb, > int option; > kuid_t uid; > kgid_t gid; > + struct block_device *journal_bdev; > + char *journal_path; > + > #ifdef CONFIG_QUOTA > int qfmt; > #endif > @@ -1129,6 +1134,31 @@ static int parse_options (char *options, struct super_block *sb, > return 0; > *journal_devnum = option; > break; > + case Opt_journal_path: > + if (is_remount) { > + ext3_msg(sb, KERN_ERR, "error: cannot specify " > + "journal on remount"); > + return 0; > + } > + journal_path = match_strdup(&args[0]); > + if (!journal_path) { > + ext3_msg(sb, KERN_ERR, "error: could not dup " > + "journal device string"); > + return 0; > + } > + journal_bdev = lookup_bdev(journal_path); > + if (IS_ERR(journal_bdev)) { > + ext3_msg(sb, KERN_ERR, "error: could not look " > + "up journal device: error %d", > + (int)PTR_ERR(journal_bdev)); > + kfree(journal_path); > + return 0; > + } > + > + *journal_devnum = new_encode_dev(journal_bdev->bd_dev); > + bdput(journal_bdev); > + kfree(journal_path); > + break; > case Opt_noload: > set_opt (sbi->s_mount_opt, NOLOAD); > break; >
On 7/31/13 9:05 AM, Jan Kara wrote: > On Tue 30-07-13 17:26:24, Eric Sandeen wrote: >> 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 /mnt >> >> 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.ext3 -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] EXT3-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> >> --- >> >> The patch is a little hacky, doing all the work in option parsing, >> just to get to a journal devnum like the old option expected, only >> to later re-decode it when we really want to open it. >> >> I could clean it up so that both journal-update mount options >> find the bdev, rather than ending with an encoded device number, >> which must then be decoded & re-opened, if that seems better. >> >> But this was expedient enough to get the idea out on the list. >> >> If we like it, I'll do ext4 as well. > Yeah, it looks like a good idea. You could just lookup the path via > kern_path() and then take the device numbers from the inode so you won't > have to do the decode-recode dance. That would look like the cleanest option > to me. > > Honza Ah, thanks for the suggestion, I'll give that a shot. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt index 293855e..7ed0d17 100644 --- a/Documentation/filesystems/ext3.txt +++ b/Documentation/filesystems/ext3.txt @@ -26,11 +26,12 @@ journal=inum When a journal already exists, this option is ignored. Otherwise, it specifies the number of the inode which will represent the ext3 file system's journal file. +journal_path=path journal_dev=devnum When the external journal device's major/minor numbers - have changed, this option allows the user to specify + have changed, these options allow the user to specify the new journal location. The journal device is - identified through its new major/minor numbers encoded - in devnum. + identified through either its new major/minor numbers + encoded in devnum, or via a path to the device. norecovery Don't load the journal on mounting. Note that this forces noload mount of inconsistent filesystem, which can lead to diff --git a/fs/ext3/super.c b/fs/ext3/super.c index c47f147..cb1dd6e 100644 --- a/fs/ext3/super.c +++ b/fs/ext3/super.c @@ -819,6 +819,7 @@ enum { Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl, Opt_reservation, Opt_noreservation, Opt_noload, Opt_nobh, Opt_bh, Opt_commit, Opt_journal_update, Opt_journal_inum, Opt_journal_dev, + Opt_journal_path, Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback, Opt_data_err_abort, Opt_data_err_ignore, Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota, @@ -860,6 +861,7 @@ static const match_table_t tokens = { {Opt_journal_update, "journal=update"}, {Opt_journal_inum, "journal=%u"}, {Opt_journal_dev, "journal_dev=%u"}, + {Opt_journal_path, "journal_path=%s"}, {Opt_abort, "abort"}, {Opt_data_journal, "data=journal"}, {Opt_data_ordered, "data=ordered"}, @@ -975,6 +977,9 @@ static int parse_options (char *options, struct super_block *sb, int option; kuid_t uid; kgid_t gid; + struct block_device *journal_bdev; + char *journal_path; + #ifdef CONFIG_QUOTA int qfmt; #endif @@ -1129,6 +1134,31 @@ static int parse_options (char *options, struct super_block *sb, return 0; *journal_devnum = option; break; + case Opt_journal_path: + if (is_remount) { + ext3_msg(sb, KERN_ERR, "error: cannot specify " + "journal on remount"); + return 0; + } + journal_path = match_strdup(&args[0]); + if (!journal_path) { + ext3_msg(sb, KERN_ERR, "error: could not dup " + "journal device string"); + return 0; + } + journal_bdev = lookup_bdev(journal_path); + if (IS_ERR(journal_bdev)) { + ext3_msg(sb, KERN_ERR, "error: could not look " + "up journal device: error %d", + (int)PTR_ERR(journal_bdev)); + kfree(journal_path); + return 0; + } + + *journal_devnum = new_encode_dev(journal_bdev->bd_dev); + bdput(journal_bdev); + kfree(journal_path); + break; case Opt_noload: set_opt (sbi->s_mount_opt, NOLOAD); break;
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 /mnt 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.ext3 -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] EXT3-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> --- The patch is a little hacky, doing all the work in option parsing, just to get to a journal devnum like the old option expected, only to later re-decode it when we really want to open it. I could clean it up so that both journal-update mount options find the bdev, rather than ending with an encoded device number, which must then be decoded & re-opened, if that seems better. But this was expedient enough to get the idea out on the list. If we like it, I'll do ext4 as well. Thanks, -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html