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Add 'zfs rename -u' to rename without remounting

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Allow to rename file systems without remounting if it is possible.
It is possible for file systems with 'mountpoint' property set to
'legacy' or 'none' - we don't have to change mount directory for them.
Currently such file systems are unmounted on rename and not even
mounted back.

This introduces layering violation, as we need to update
'f_mntfromname' field in statfs structure related to mountpoint (for
the dataset we are renaming and all its children).

In my opinion it is worth it, as it allow to update FreeBSD in even
cleaner way - in ZFS-only configuration root file system is ZFS file
system with 'mountpoint' property set to 'legacy'. If root dataset is
named system/rootfs, we can snapshot it (system/rootfs@upgrade), clone
it (system/oldrootfs), update FreeBSD and if it doesn't boot we can
boot back from system/oldrootfs and rename it back to system/rootfs
while it is mounted as /. Before it was not possible, because
unmounting / was not possible.

Authored by: Pawel Jakub Dawidek <pjd@FreeBSD.org>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported by: Matt Macy <mmacy@freebsd.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10839
This commit is contained in:
Ryan Moeller
2020-09-01 19:14:16 -04:00
committed by Brian Behlendorf
parent 6512c18fe1
commit 76a157f004
21 changed files with 284 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/os/linux/zfs/zfs_vfsops.c
+10
View File
@@ -2126,6 +2126,16 @@ zfs_get_vfs_flag_unmounted(objset_t *os)
return (unmounted);
}
/*ARGSUSED*/
void
zfsvfs_update_fromname(const char *oldname, const char *newname)
{
/*
* We don't need to do anything here, the devname is always current by
* virtue of zfsvfs->z_sb->s_op->show_devname.
*/
}
void
zfs_init(void)
{
module/os/linux/zfs/zpl_super.c
+20
View File
@@ -182,6 +182,25 @@ zpl_remount_fs(struct super_block *sb, int *flags, char *data)
return (error);
}
static int
__zpl_show_devname(struct seq_file *seq, zfsvfs_t *zfsvfs)
{
char *fsname;
fsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
dmu_objset_name(zfsvfs->z_os, fsname);
seq_puts(seq, fsname);
kmem_free(fsname, ZFS_MAX_DATASET_NAME_LEN);
return (0);
}
static int
zpl_show_devname(struct seq_file *seq, struct dentry *root)
{
return (__zpl_show_devname(seq, root->d_sb->s_fs_info));
}
static int
__zpl_show_options(struct seq_file *seq, zfsvfs_t *zfsvfs)
{
@@ -314,6 +333,7 @@ const struct super_operations zpl_super_operations = {
.sync_fs = zpl_sync_fs,
.statfs = zpl_statfs,
.remount_fs = zpl_remount_fs,
.show_devname = zpl_show_devname,
.show_options = zpl_show_options,
.show_stats = NULL,
};