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Btrfs: Add readonly snapshots support

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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: Li Zefan <lizf@cn.fujitsu.com>
This commit is contained in:
Li Zefan 2010-12-20 16:04:08 +08:00
parent fa0d2b9bd7
commit b83cc9693f
7 changed files with 75 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/btrfs/ctree.h
View File

@ -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);

8
fs/btrfs/inode.c
View File

@ -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);

42
fs/btrfs/ioctl.c
View File

@ -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 @@ static noinline int create_subvol(struct btrfs_root *root,
}
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;

1
fs/btrfs/ioctl.h
View File

@ -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 {

8
fs/btrfs/transaction.c
View File

@ -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);

1
fs/btrfs/transaction.h
View File

@ -62,6 +62,7 @@ struct btrfs_pending_snapshot {
struct btrfs_block_rsv block_rsv;
/* extra metadata reseration for relocation */
int error;
bool readonly;
struct list_head list;
};

18
fs/btrfs/xattr.c
View File

@ -316,6 +316,15 @@ ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags)
{
struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
/*
* The permission on security.* and system.* is not checked
* in permission().
*/
if (btrfs_root_readonly(root))
return -EROFS;
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler
@ -336,6 +345,15 @@ int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
int btrfs_removexattr(struct dentry *dentry, const char *name)
{
struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
/*
* The permission on security.* and system.* is not checked
* in permission().
*/
if (btrfs_root_readonly(root))
return -EROFS;
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler