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: Li Zefan <lizf@cn.fujitsu.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index af52f6d..4403e56 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -597,6 +597,8 @@
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_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);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5f91944..956f1eb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3671,8 +3671,12 @@
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_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);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 02554e1..f066ccb 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -147,6 +147,9 @@
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 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 @@
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 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 @@
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 @@
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 @@
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 @@
}
ret = btrfs_mksubvol(&file->f_path, name, namelen,
BTRFS_I(src_inode)->root,
- transid);
+ transid, readonly);
fput(src_file);
}
out:
@@ -957,7 +963,8 @@
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 @@
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 @@
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 @@
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 @@
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;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index c344d12..52ae489 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -31,6 +31,7 @@
};
#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 {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index f50e931..29e30d8 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -910,6 +910,7 @@
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 @@
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);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index f104b57..229a594 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -62,6 +62,7 @@
struct btrfs_block_rsv block_rsv;
/* extra metadata reseration for relocation */
int error;
+ bool readonly;
struct list_head list;
};
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 698fdd2..a577653 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -316,6 +316,15 @@
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_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
