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Btrfs: Add readonly snapshots support

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

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 @@ 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;