Commit e15d0542 authored by Xin Zhong's avatar Xin Zhong Committed by Chris Mason
Browse files

Btrfs: fix subvolume mount by name problem when default mount subvolume is set 

We create two subvolumes (meego_root and meego_home) in
btrfs root directory. And set meego_root as default mount
subvolume. After we remount btrfs, meego_root is mounted
to top directory by default. Then when we try to mount
meego_home (subvol=meego_home) to a subdirectory, it failed.
The problem is when default mount subvolume is set to
meego_root, we search meego_home in meego_root but can not find
it. So the solution is to add a new mount option (subvolrootid)
to specify subvol id of root and search subvol name in it. For
our case, now we can use "-o subvolrootid=0,subvol=meego_home)
to mount meego_home.

Detail information can be found in meego bugzilla:
https://bugs.meego.com/show_bug.cgi?id=15055



Signed-off-by: default avatarZhong, Xin <xin.zhong@intel.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 13f2696f

fs/btrfs/super.c

+33 −9
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ enum { 
	Opt_compress_type, Opt_compress_force, Opt_compress_force_type,

	Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_discard,

	Opt_space_cache, Opt_clear_cache, Opt_user_subvol_rm_allowed,

	Opt_enospc_debug, Opt_err,

	Opt_enospc_debug, Opt_subvolrootid, Opt_err,

};



static match_table_t tokens = {
@@ -189,6 +189,7 @@ static match_table_t tokens = { 
	{Opt_clear_cache, "clear_cache"},

	{Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},

	{Opt_enospc_debug, "enospc_debug"},

	{Opt_subvolrootid, "subvolrootid=%d"},

	{Opt_err, NULL},

};
@@ -232,6 +233,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options) 
			break;

		case Opt_subvol:

		case Opt_subvolid:

		case Opt_subvolrootid:

		case Opt_device:

			/*

			 * These are parsed by btrfs_parse_early_options
@@ -388,7 +390,7 @@ out: 
 */

static int btrfs_parse_early_options(const char *options, fmode_t flags,

		void *holder, char **subvol_name, u64 *subvol_objectid,

		struct btrfs_fs_devices **fs_devices)

		u64 *subvol_rootid, struct btrfs_fs_devices **fs_devices)

{

	substring_t args[MAX_OPT_ARGS];

	char *opts, *orig, *p;
@@ -429,6 +431,18 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags, 
					*subvol_objectid = intarg;

			}

			break;

		case Opt_subvolrootid:

			intarg = 0;

			error = match_int(&args[0], &intarg);

			if (!error) {

				/* we want the original fs_tree */

				if (!intarg)

					*subvol_rootid =

						BTRFS_FS_TREE_OBJECTID;

				else

					*subvol_rootid = intarg;

			}

			break;

		case Opt_device:

			error = btrfs_scan_one_device(match_strdup(&args[0]),

					flags, holder, fs_devices);
@@ -736,6 +750,7 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
	fmode_t mode = FMODE_READ;

	char *subvol_name = NULL;

	u64 subvol_objectid = 0;

	u64 subvol_rootid = 0;

	int error = 0;



	if (!(flags & MS_RDONLY))
@@ -743,7 +758,7 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 


	error = btrfs_parse_early_options(data, mode, fs_type,

					  &subvol_name, &subvol_objectid,

					  &fs_devices);

					  &subvol_rootid, &fs_devices);

	if (error)

		return ERR_PTR(error);
@@ -807,15 +822,17 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
		s->s_flags |= MS_ACTIVE;

	}



	root = get_default_root(s, subvol_objectid);

	/* 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;

		}

	/* if they gave us a subvolume name bind mount into that */

	if (strcmp(subvol_name, ".")) {

		struct dentry *new_root;



		mutex_lock(&root->d_inode->i_mutex);

		new_root = lookup_one_len(subvol_name, root,

				      strlen(subvol_name));
@@ -836,6 +853,13 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
		}

		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;

		}

	}



	kfree(subvol_name);

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