Commit b83cc969 authored by Li Zefan's avatar Li Zefan
Browse files

Btrfs: Add readonly snapshots support 



Usage:

Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and call
ioctl(BTRFS_I0CTL_SNAP_CREATE_V2).

Implementation:

- Set readonly bit of btrfs_root_item->flags.
- Add readonly checks in btrfs_permission (inode_permission),
btrfs_setattr, btrfs_set/remove_xattr and some ioctls.

Changelog for v3:

- Eliminate btrfs_root->readonly, but check btrfs_root->root_item.flags.
- Rename BTRFS_ROOT_SNAP_RDONLY to BTRFS_ROOT_SUBVOL_RDONLY.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
parent fa0d2b9b

fs/btrfs/ctree.h

+7 −0
Original line number Diff line number Diff line
@@ -597,6 +597,8 @@ struct btrfs_dir_item { 
	u8 type;

} __attribute__ ((__packed__));



#define BTRFS_ROOT_SUBVOL_RDONLY	(1ULL << 0)



struct btrfs_root_item {

	struct btrfs_inode_item inode;

	__le64 generation;
@@ -1893,6 +1895,11 @@ BTRFS_SETGET_STACK_FUNCS(root_limit, struct btrfs_root_item, byte_limit, 64); 
BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct btrfs_root_item,

			 last_snapshot, 64);



static inline bool btrfs_root_readonly(struct btrfs_root *root)

{

	return root->root_item.flags & BTRFS_ROOT_SUBVOL_RDONLY;

}



/* struct btrfs_super_block */



BTRFS_SETGET_STACK_FUNCS(super_bytenr, struct btrfs_super_block, bytenr, 64);

fs/btrfs/inode.c

+8 −0
Original line number Diff line number Diff line
@@ -3671,8 +3671,12 @@ static int btrfs_setattr_size(struct inode *inode, struct iattr *attr) 
static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)

{

	struct inode *inode = dentry->d_inode;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	int err;



	if (btrfs_root_readonly(root))

		return -EROFS;



	err = inode_change_ok(inode, attr);

	if (err)

		return err;
@@ -7206,6 +7210,10 @@ static int btrfs_set_page_dirty(struct page *page) 


static int btrfs_permission(struct inode *inode, int mask)

{

	struct btrfs_root *root = BTRFS_I(inode)->root;



	if (btrfs_root_readonly(root) && (mask & MAY_WRITE))

		return -EROFS;

	if ((BTRFS_I(inode)->flags & BTRFS_INODE_READONLY) && (mask & MAY_WRITE))

		return -EACCES;

	return generic_permission(inode, mask, btrfs_check_acl);

fs/btrfs/ioctl.c

+32 −10
Original line number Diff line number Diff line
@@ -147,6 +147,9 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg) 
	unsigned int flags, oldflags;

	int ret;



	if (btrfs_root_readonly(root))

		return -EROFS;



	if (copy_from_user(&flags, arg, sizeof(flags)))

		return -EFAULT;
@@ -360,7 +363,8 @@ fail: 
}



static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,

			   char *name, int namelen, u64 *async_transid)

			   char *name, int namelen, u64 *async_transid,

			   bool readonly)

{

	struct inode *inode;

	struct dentry *parent;
@@ -378,6 +382,7 @@ static int create_snapshot(struct btrfs_root *root, struct dentry *dentry, 
	btrfs_init_block_rsv(&pending_snapshot->block_rsv);

	pending_snapshot->dentry = dentry;

	pending_snapshot->root = root;

	pending_snapshot->readonly = readonly;



	trans = btrfs_start_transaction(root->fs_info->extent_root, 5);

	if (IS_ERR(trans)) {
@@ -509,7 +514,7 @@ static inline int btrfs_may_create(struct inode *dir, struct dentry *child) 
static noinline int btrfs_mksubvol(struct path *parent,

				   char *name, int namelen,

				   struct btrfs_root *snap_src,

				   u64 *async_transid)

				   u64 *async_transid, bool readonly)

{

	struct inode *dir  = parent->dentry->d_inode;

	struct dentry *dentry;
@@ -541,7 +546,7 @@ static noinline int btrfs_mksubvol(struct path *parent, 


	if (snap_src) {

		error = create_snapshot(snap_src, dentry,

					name, namelen, async_transid);

					name, namelen, async_transid, readonly);

	} else {

		error = create_subvol(BTRFS_I(dir)->root, dentry,

				      name, namelen, async_transid);
@@ -901,7 +906,8 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file, 
						    char *name,

						    unsigned long fd,

						    int subvol,

						    u64 *transid)

						    u64 *transid,

						    bool readonly)

{

	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;

	struct file *src_file;
@@ -919,7 +925,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file, 


	if (subvol) {

		ret = btrfs_mksubvol(&file->f_path, name, namelen,

				     NULL, transid);

				     NULL, transid, readonly);

	} else {

		struct inode *src_inode;

		src_file = fget(fd);
@@ -938,7 +944,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file, 
		}

		ret = btrfs_mksubvol(&file->f_path, name, namelen,

				     BTRFS_I(src_inode)->root,

				     transid);

				     transid, readonly);

		fput(src_file);

	}

out:
@@ -957,7 +963,8 @@ static noinline int btrfs_ioctl_snap_create(struct file *file, 
	vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';



	ret = btrfs_ioctl_snap_create_transid(file, vol_args->name,

					      vol_args->fd, subvol, NULL);

					      vol_args->fd, subvol,

					      NULL, false);



	kfree(vol_args);

	return ret;
@@ -970,22 +977,27 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file, 
	int ret;

	u64 transid = 0;

	u64 *ptr = NULL;

	bool readonly = false;



	vol_args = memdup_user(arg, sizeof(*vol_args));

	if (IS_ERR(vol_args))

		return PTR_ERR(vol_args);

	vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';



	if (vol_args->flags & ~BTRFS_SUBVOL_CREATE_ASYNC) {

		ret = -EINVAL;

	if (vol_args->flags &

	    ~(BTRFS_SUBVOL_CREATE_ASYNC | BTRFS_SUBVOL_RDONLY)) {

		ret = -EOPNOTSUPP;

		goto out;

	}



	if (vol_args->flags & BTRFS_SUBVOL_CREATE_ASYNC)

		ptr = &transid;

	if (vol_args->flags & BTRFS_SUBVOL_RDONLY)

		readonly = true;



	ret = btrfs_ioctl_snap_create_transid(file, vol_args->name,

					      vol_args->fd, subvol, ptr);

					      vol_args->fd, subvol,

					      ptr, readonly);



	if (ret == 0 && ptr &&

	    copy_to_user(arg +
@@ -1505,6 +1517,9 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp) 
	struct btrfs_ioctl_defrag_range_args *range;

	int ret;



	if (btrfs_root_readonly(root))

		return -EROFS;



	ret = mnt_want_write(file->f_path.mnt);

	if (ret)

		return ret;
@@ -1633,6 +1648,9 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd, 
	if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))

		return -EINVAL;



	if (btrfs_root_readonly(root))

		return -EROFS;



	ret = mnt_want_write(file->f_path.mnt);

	if (ret)

		return ret;
@@ -1954,6 +1972,10 @@ static long btrfs_ioctl_trans_start(struct file *file) 
	if (file->private_data)

		goto out;



	ret = -EROFS;

	if (btrfs_root_readonly(root))

		goto out;



	ret = mnt_want_write(file->f_path.mnt);

	if (ret)

		goto out;

fs/btrfs/ioctl.h

+1 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ struct btrfs_ioctl_vol_args { 
};



#define BTRFS_SUBVOL_CREATE_ASYNC	(1ULL << 0)

#define BTRFS_SUBVOL_RDONLY		(1ULL << 1)



#define BTRFS_SUBVOL_NAME_MAX 4039

struct btrfs_ioctl_vol_args_v2 {

fs/btrfs/transaction.c

+8 −0
Original line number Diff line number Diff line
@@ -910,6 +910,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, 
	u64 to_reserve = 0;

	u64 index = 0;

	u64 objectid;

	u64 root_flags;



	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);

	if (!new_root_item) {
@@ -967,6 +968,13 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, 
	btrfs_set_root_last_snapshot(&root->root_item, trans->transid);

	memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));



	root_flags = btrfs_root_flags(new_root_item);

	if (pending->readonly)

		root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;

	else

		root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;

	btrfs_set_root_flags(new_root_item, root_flags);



	old = btrfs_lock_root_node(root);

	btrfs_cow_block(trans, root, old, NULL, 0, &old);

	btrfs_set_lock_blocking(old);

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