Btrfs: fix how we mount subvol=<whatever>

We've only been able to mount with subvol=<whatever> where whatever was a subvol
within whatever root we had as the default.  This allows us to mount -o
subvol=path/to/subvol/you/want relative from the normal fs_tree root.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
This commit is contained in:
Josef Bacik 2011-07-25 15:55:42 -04:00
Родитель ba5b8958da
Коммит 830c4adbd0
1 изменённых файлов: 135 добавлений и 64 удалений

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@ -40,6 +40,7 @@
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/cleancache.h>
#include <linux/mnt_namespace.h>
#include "compat.h"
#include "delayed-inode.h"
#include "ctree.h"
@ -58,6 +59,7 @@
#include <trace/events/btrfs.h>
static const struct super_operations btrfs_super_ops;
static struct file_system_type btrfs_fs_type;
static const char *btrfs_decode_error(struct btrfs_fs_info *fs_info, int errno,
char nbuf[16])
@ -411,7 +413,7 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
int intarg;
if (!options)
goto out;
return 0;
/*
* strsep changes the string, duplicate it because parse_options
@ -460,26 +462,15 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
error = btrfs_scan_one_device(match_strdup(&args[0]),
flags, holder, fs_devices);
if (error)
goto out_free_opts;
goto out;
break;
default:
break;
}
}
out_free_opts:
out:
kfree(orig);
out:
/*
* If no subvolume name is specified we use the default one. Allocate
* a copy of the string "." here so that code later in the
* mount path doesn't care if it's the default volume or another one.
*/
if (!*subvol_name) {
*subvol_name = kstrdup(".", GFP_KERNEL);
if (!*subvol_name)
return -ENOMEM;
}
return error;
}
@ -730,6 +721,118 @@ static int btrfs_set_super(struct super_block *s, void *data)
return set_anon_super(s, data);
}
/*
* This will strip out the subvol=%s argument for an argument string and add
* subvolid=0 to make sure we get the actual tree root for path walking to the
* subvol we want.
*/
static char *setup_root_args(char *args)
{
unsigned copied = 0;
unsigned len = strlen(args) + 2;
char *pos;
char *ret;
/*
* We need the same args as before, but minus
*
* subvol=a
*
* and add
*
* subvolid=0
*
* which is a difference of 2 characters, so we allocate strlen(args) +
* 2 characters.
*/
ret = kzalloc(len * sizeof(char), GFP_NOFS);
if (!ret)
return NULL;
pos = strstr(args, "subvol=");
/* This shouldn't happen, but just in case.. */
if (!pos) {
kfree(ret);
return NULL;
}
/*
* The subvol=<> arg is not at the front of the string, copy everybody
* up to that into ret.
*/
if (pos != args) {
*pos = '\0';
strcpy(ret, args);
copied += strlen(args);
pos++;
}
strncpy(ret + copied, "subvolid=0", len - copied);
/* Length of subvolid=0 */
copied += 10;
/*
* If there is no , after the subvol= option then we know there's no
* other options and we can just return.
*/
pos = strchr(pos, ',');
if (!pos)
return ret;
/* Copy the rest of the arguments into our buffer */
strncpy(ret + copied, pos, len - copied);
copied += strlen(pos);
return ret;
}
static struct dentry *mount_subvol(const char *subvol_name, int flags,
const char *device_name, char *data)
{
struct super_block *s;
struct dentry *root;
struct vfsmount *mnt;
struct mnt_namespace *ns_private;
char *newargs;
struct path path;
int error;
newargs = setup_root_args(data);
if (!newargs)
return ERR_PTR(-ENOMEM);
mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
newargs);
kfree(newargs);
if (IS_ERR(mnt))
return ERR_CAST(mnt);
ns_private = create_mnt_ns(mnt);
if (IS_ERR(ns_private)) {
mntput(mnt);
return ERR_CAST(ns_private);
}
/*
* This will trigger the automount of the subvol so we can just
* drop the mnt we have here and return the dentry that we
* found.
*/
error = vfs_path_lookup(mnt->mnt_root, mnt, subvol_name,
LOOKUP_FOLLOW, &path);
put_mnt_ns(ns_private);
if (error)
return ERR_PTR(error);
/* Get a ref to the sb and the dentry we found and return it */
s = path.mnt->mnt_sb;
atomic_inc(&s->s_active);
root = dget(path.dentry);
path_put(&path);
down_write(&s->s_umount);
return root;
}
/*
* Find a superblock for the given device / mount point.
@ -761,13 +864,19 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
if (error)
return ERR_PTR(error);
if (subvol_name) {
root = mount_subvol(subvol_name, flags, device_name, data);
kfree(subvol_name);
return root;
}
error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
if (error)
goto error_free_subvol_name;
return ERR_PTR(error);
error = btrfs_open_devices(fs_devices, mode, fs_type);
if (error)
goto error_free_subvol_name;
return ERR_PTR(error);
if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
error = -EACCES;
@ -792,14 +901,15 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
bdev = fs_devices->latest_bdev;
s = sget(fs_type, btrfs_test_super, btrfs_set_super, tree_root);
if (IS_ERR(s))
goto error_s;
if (IS_ERR(s)) {
error = PTR_ERR(s);
goto error_close_devices;
}
if (s->s_root) {
if ((flags ^ s->s_flags) & MS_RDONLY) {
deactivate_locked_super(s);
error = -EBUSY;
goto error_close_devices;
return ERR_PTR(-EBUSY);
}
btrfs_close_devices(fs_devices);
@ -814,64 +924,25 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
goto error_free_subvol_name;
return ERR_PTR(error);
}
btrfs_sb(s)->fs_info->bdev_holder = fs_type;
s->s_flags |= MS_ACTIVE;
}
/* if they gave us a subvolume name bind mount into that */
if (strcmp(subvol_name, ".")) {
struct dentry *new_root;
root = get_default_root(s, subvol_rootid);
if (IS_ERR(root)) {
error = PTR_ERR(root);
deactivate_locked_super(s);
goto error_free_subvol_name;
}
mutex_lock(&root->d_inode->i_mutex);
new_root = lookup_one_len(subvol_name, root,
strlen(subvol_name));
mutex_unlock(&root->d_inode->i_mutex);
if (IS_ERR(new_root)) {
dput(root);
deactivate_locked_super(s);
error = PTR_ERR(new_root);
goto error_free_subvol_name;
}
if (!new_root->d_inode) {
dput(root);
dput(new_root);
deactivate_locked_super(s);
error = -ENXIO;
goto error_free_subvol_name;
}
dput(root);
root = new_root;
} else {
root = get_default_root(s, subvol_objectid);
if (IS_ERR(root)) {
error = PTR_ERR(root);
deactivate_locked_super(s);
goto error_free_subvol_name;
}
root = get_default_root(s, subvol_objectid);
if (IS_ERR(root)) {
deactivate_locked_super(s);
return root;
}
kfree(subvol_name);
return root;
error_s:
error = PTR_ERR(s);
error_close_devices:
btrfs_close_devices(fs_devices);
kfree(fs_info);
kfree(tree_root);
error_free_subvol_name:
kfree(subvol_name);
return ERR_PTR(error);
}