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Btrfs: Add BTRFS_IOC_SUBVOL_GETFLAGS/SETFLAGS ioctls 

This allows us to set a snapshot or a subvolume readonly or writable
on the fly.

Usage:

Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and then
call ioctl(BTRFS_IOCTL_SUBVOL_SETFLAGS);

Changelog for v3:

- Change to pass __u64 as ioctl parameter.

Changelog for v2:

- Add _GETFLAGS ioctl.
- Check if the passed fd is the root of a subvolume.
- Change the name from _SNAP_SETFLAGS to _SUBVOL_SETFLAGS.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
This commit is contained in:
Li Zefan 2010-12-20 16:30:25 +08:00
parent b83cc9693f
commit 0caa102da8
2 changed files with 85 additions and 0 deletions
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83
fs/btrfs/ioctl.c
View File

@ -1009,6 +1009,85 @@ out:
return ret;
}
static noinline int btrfs_ioctl_subvol_getflags(struct file *file,
void __user *arg)
{
struct inode *inode = fdentry(file)->d_inode;
struct btrfs_root *root = BTRFS_I(inode)->root;
int ret = 0;
u64 flags = 0;
if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)
return -EINVAL;
down_read(&root->fs_info->subvol_sem);
if (btrfs_root_readonly(root))
flags |= BTRFS_SUBVOL_RDONLY;
up_read(&root->fs_info->subvol_sem);
if (copy_to_user(arg, &flags, sizeof(flags)))
ret = -EFAULT;
return ret;
}
static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
void __user *arg)
{
struct inode *inode = fdentry(file)->d_inode;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_trans_handle *trans;
u64 root_flags;
u64 flags;
int ret = 0;
if (root->fs_info->sb->s_flags & MS_RDONLY)
return -EROFS;
if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)
return -EINVAL;
if (copy_from_user(&flags, arg, sizeof(flags)))
return -EFAULT;
if (flags & ~BTRFS_SUBVOL_CREATE_ASYNC)
return -EINVAL;
if (flags & ~BTRFS_SUBVOL_RDONLY)
return -EOPNOTSUPP;
down_write(&root->fs_info->subvol_sem);
/* nothing to do */
if (!!(flags & BTRFS_SUBVOL_RDONLY) == btrfs_root_readonly(root))
goto out;
root_flags = btrfs_root_flags(&root->root_item);
if (flags & BTRFS_SUBVOL_RDONLY)
btrfs_set_root_flags(&root->root_item,
root_flags | BTRFS_ROOT_SUBVOL_RDONLY);
else
btrfs_set_root_flags(&root->root_item,
root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
trans = btrfs_start_transaction(root, 1);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out_reset;
}
ret = btrfs_update_root(trans, root,
&root->root_key, &root->root_item);
btrfs_commit_transaction(trans, root);
out_reset:
if (ret)
btrfs_set_root_flags(&root->root_item, root_flags);
out:
up_write(&root->fs_info->subvol_sem);
return ret;
}
/*
* helper to check if the subvolume references other subvolumes
*/
@ -2282,6 +2361,10 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_snap_create(file, argp, 1);
case BTRFS_IOC_SNAP_DESTROY:
return btrfs_ioctl_snap_destroy(file, argp);
case BTRFS_IOC_SUBVOL_GETFLAGS:
return btrfs_ioctl_subvol_getflags(file, argp);
case BTRFS_IOC_SUBVOL_SETFLAGS:
return btrfs_ioctl_subvol_setflags(file, argp);
case BTRFS_IOC_DEFAULT_SUBVOL:
return btrfs_ioctl_default_subvol(file, argp);
case BTRFS_IOC_DEFRAG:

2
fs/btrfs/ioctl.h
View File

@ -194,4 +194,6 @@ struct btrfs_ioctl_space_args {
#define BTRFS_IOC_WAIT_SYNC _IOW(BTRFS_IOCTL_MAGIC, 22, __u64)
#define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \
struct btrfs_ioctl_vol_args_v2)
#define BTRFS_IOC_SUBVOL_GETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 25, __u64)
#define BTRFS_IOC_SUBVOL_SETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 26, __u64)
#endif