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
Родитель
ba5b8958da
Коммит
830c4adbd0
199
fs/btrfs/super.c
199
fs/btrfs/super.c
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@ -40,6 +40,7 @@
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#include <linux/magic.h>
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#include <linux/slab.h>
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#include <linux/cleancache.h>
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#include <linux/mnt_namespace.h>
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#include "compat.h"
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#include "delayed-inode.h"
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#include "ctree.h"
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@ -58,6 +59,7 @@
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#include <trace/events/btrfs.h>
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static const struct super_operations btrfs_super_ops;
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static struct file_system_type btrfs_fs_type;
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static const char *btrfs_decode_error(struct btrfs_fs_info *fs_info, int errno,
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char nbuf[16])
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@ -411,7 +413,7 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
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int intarg;
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if (!options)
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goto out;
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return 0;
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/*
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* strsep changes the string, duplicate it because parse_options
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@ -460,26 +462,15 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
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error = btrfs_scan_one_device(match_strdup(&args[0]),
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flags, holder, fs_devices);
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if (error)
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goto out_free_opts;
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goto out;
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break;
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default:
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break;
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}
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}
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out_free_opts:
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out:
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kfree(orig);
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out:
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/*
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* If no subvolume name is specified we use the default one. Allocate
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* a copy of the string "." here so that code later in the
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* mount path doesn't care if it's the default volume or another one.
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*/
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if (!*subvol_name) {
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*subvol_name = kstrdup(".", GFP_KERNEL);
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if (!*subvol_name)
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return -ENOMEM;
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}
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return error;
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}
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@ -730,6 +721,118 @@ static int btrfs_set_super(struct super_block *s, void *data)
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return set_anon_super(s, data);
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}
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/*
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* This will strip out the subvol=%s argument for an argument string and add
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* subvolid=0 to make sure we get the actual tree root for path walking to the
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* subvol we want.
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*/
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static char *setup_root_args(char *args)
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{
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unsigned copied = 0;
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unsigned len = strlen(args) + 2;
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char *pos;
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char *ret;
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/*
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* We need the same args as before, but minus
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*
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* subvol=a
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*
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* and add
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*
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* subvolid=0
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*
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* which is a difference of 2 characters, so we allocate strlen(args) +
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* 2 characters.
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*/
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ret = kzalloc(len * sizeof(char), GFP_NOFS);
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if (!ret)
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return NULL;
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pos = strstr(args, "subvol=");
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/* This shouldn't happen, but just in case.. */
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if (!pos) {
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kfree(ret);
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return NULL;
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}
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/*
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* The subvol=<> arg is not at the front of the string, copy everybody
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* up to that into ret.
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*/
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if (pos != args) {
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*pos = '\0';
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strcpy(ret, args);
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copied += strlen(args);
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pos++;
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}
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strncpy(ret + copied, "subvolid=0", len - copied);
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/* Length of subvolid=0 */
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copied += 10;
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/*
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* If there is no , after the subvol= option then we know there's no
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* other options and we can just return.
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*/
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pos = strchr(pos, ',');
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if (!pos)
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return ret;
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/* Copy the rest of the arguments into our buffer */
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strncpy(ret + copied, pos, len - copied);
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copied += strlen(pos);
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return ret;
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}
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static struct dentry *mount_subvol(const char *subvol_name, int flags,
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const char *device_name, char *data)
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{
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struct super_block *s;
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struct dentry *root;
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struct vfsmount *mnt;
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struct mnt_namespace *ns_private;
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char *newargs;
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struct path path;
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int error;
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newargs = setup_root_args(data);
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if (!newargs)
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return ERR_PTR(-ENOMEM);
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mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
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newargs);
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kfree(newargs);
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if (IS_ERR(mnt))
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return ERR_CAST(mnt);
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ns_private = create_mnt_ns(mnt);
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if (IS_ERR(ns_private)) {
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mntput(mnt);
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return ERR_CAST(ns_private);
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}
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/*
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* This will trigger the automount of the subvol so we can just
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* drop the mnt we have here and return the dentry that we
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* found.
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*/
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error = vfs_path_lookup(mnt->mnt_root, mnt, subvol_name,
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LOOKUP_FOLLOW, &path);
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put_mnt_ns(ns_private);
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if (error)
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return ERR_PTR(error);
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/* Get a ref to the sb and the dentry we found and return it */
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s = path.mnt->mnt_sb;
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atomic_inc(&s->s_active);
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root = dget(path.dentry);
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path_put(&path);
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down_write(&s->s_umount);
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return root;
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}
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/*
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* Find a superblock for the given device / mount point.
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@ -761,13 +864,19 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
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if (error)
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return ERR_PTR(error);
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if (subvol_name) {
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root = mount_subvol(subvol_name, flags, device_name, data);
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kfree(subvol_name);
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return root;
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}
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error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
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if (error)
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goto error_free_subvol_name;
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return ERR_PTR(error);
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error = btrfs_open_devices(fs_devices, mode, fs_type);
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if (error)
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goto error_free_subvol_name;
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return ERR_PTR(error);
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if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
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error = -EACCES;
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@ -792,14 +901,15 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
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bdev = fs_devices->latest_bdev;
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s = sget(fs_type, btrfs_test_super, btrfs_set_super, tree_root);
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if (IS_ERR(s))
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goto error_s;
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if (IS_ERR(s)) {
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error = PTR_ERR(s);
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goto error_close_devices;
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}
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if (s->s_root) {
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if ((flags ^ s->s_flags) & MS_RDONLY) {
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deactivate_locked_super(s);
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error = -EBUSY;
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goto error_close_devices;
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return ERR_PTR(-EBUSY);
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}
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btrfs_close_devices(fs_devices);
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@ -814,64 +924,25 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
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flags & MS_SILENT ? 1 : 0);
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if (error) {
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deactivate_locked_super(s);
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goto error_free_subvol_name;
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return ERR_PTR(error);
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}
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btrfs_sb(s)->fs_info->bdev_holder = fs_type;
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s->s_flags |= MS_ACTIVE;
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}
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/* if they gave us a subvolume name bind mount into that */
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if (strcmp(subvol_name, ".")) {
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struct dentry *new_root;
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root = get_default_root(s, subvol_rootid);
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if (IS_ERR(root)) {
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error = PTR_ERR(root);
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deactivate_locked_super(s);
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goto error_free_subvol_name;
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}
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mutex_lock(&root->d_inode->i_mutex);
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new_root = lookup_one_len(subvol_name, root,
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strlen(subvol_name));
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mutex_unlock(&root->d_inode->i_mutex);
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if (IS_ERR(new_root)) {
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dput(root);
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deactivate_locked_super(s);
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error = PTR_ERR(new_root);
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goto error_free_subvol_name;
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}
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if (!new_root->d_inode) {
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dput(root);
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dput(new_root);
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deactivate_locked_super(s);
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error = -ENXIO;
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goto error_free_subvol_name;
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}
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dput(root);
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root = new_root;
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} else {
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root = get_default_root(s, subvol_objectid);
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if (IS_ERR(root)) {
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error = PTR_ERR(root);
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deactivate_locked_super(s);
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goto error_free_subvol_name;
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}
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root = get_default_root(s, subvol_objectid);
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if (IS_ERR(root)) {
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deactivate_locked_super(s);
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return root;
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}
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kfree(subvol_name);
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return root;
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error_s:
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error = PTR_ERR(s);
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error_close_devices:
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btrfs_close_devices(fs_devices);
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kfree(fs_info);
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kfree(tree_root);
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error_free_subvol_name:
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kfree(subvol_name);
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return ERR_PTR(error);
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}
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