From b83cc9693f39689490970c19f6c5b866f6719a70 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Mon, 20 Dec 2010 16:04:08 +0800 Subject: [PATCH] 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 --- fs/btrfs/ctree.h | 7 +++++++ fs/btrfs/inode.c | 8 ++++++++ fs/btrfs/ioctl.c | 42 ++++++++++++++++++++++++++++++++---------- fs/btrfs/ioctl.h | 1 + fs/btrfs/transaction.c | 8 ++++++++ fs/btrfs/transaction.h | 1 + fs/btrfs/xattr.c | 18 ++++++++++++++++++ 7 files changed, 75 insertions(+), 10 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index af52f6d7a4d..4403e5643d4 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -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); diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5f9194438f7..956f1eb913b 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -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); diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 02554e19d97..f066ccb5ddd 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -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; diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h index c344d12c646..52ae489974b 100644 --- a/fs/btrfs/ioctl.h +++ b/fs/btrfs/ioctl.h @@ -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 { diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index f50e931fc21..29e30d832ec 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -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); diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h index f104b57ad4e..229a594cacd 100644 --- a/fs/btrfs/transaction.h +++ b/fs/btrfs/transaction.h @@ -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; }; diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c index 698fdd2c739..a5776531dc2 100644 --- a/fs/btrfs/xattr.c +++ b/fs/btrfs/xattr.c @@ -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 -- 2.39.2