[001/001] btrfs: Mechanism to modify the permission of a subvolume
diff mbox

Message ID 1C24A869E87C7B45BE3E2BB439AB8F8C0D13DAE0@G5W2738.americas.hpqcorp.net
State Changes Requested
Headers show

Commit Message

J S, Ajesh April 23, 2014, 1:28 p.m. UTC
From: Ajesh JS <ajesh.js@hp.com>

This patch provides a mechanism to modify the permission of a subvolume in a btrfs file system
This helps to apply a policy of having read-write subvolume inside a read-only subvolume.
One use case is to have the whole root file system as a read-only subvolume and have /etc as a read-write subvolume inside.

Signed-off-by: Ajesh JS <ajesh.js@hp.com>
Reviewed-by: Liverance Fletcher <fletch@hp.com>; Clemenceau, <Matthieu matthieu.clemenceau@hp.com>
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Comments

Filipe Manana April 23, 2014, 7:38 p.m. UTC | #1
On Wed, Apr 23, 2014 at 2:28 PM, J S, Ajesh <ajesh.js@hp.com> wrote:
> From: Ajesh JS <ajesh.js@hp.com>
>
> This patch provides a mechanism to modify the permission of a subvolume in a btrfs file system
> This helps to apply a policy of having read-write subvolume inside a read-only subvolume.
> One use case is to have the whole root file system as a read-only subvolume and have /etc as a read-write subvolume inside.

Hi,

Why doesn't the existing properties feature (3.14) work for you?

Example:

$ mkfs.btrfs -f /dev/sdd
$ mount /dev/sdd /mnt/sdd

$ btrfs subvolume create /mnt/sdd/topsubvol
$ btrfs subvolume create /mnt/sdd/topsubvol/child

$ btrfs property set /mnt/sdd/topsubvol ro true

$ touch /mnt/sdd/topsubvol/file
$ touch: cannot touch ‘/mnt/sdd/topsubvol/file’: Read-only file system

$ touch /mnt/sdd/topsubvol/child/file

The property set/get just uses the ioctls BTRFS_IOC_SUBVOL_SETFLAGS
and BTRFS_IOC_SUBVOL_GETFLAGS.

thanks


>
> Signed-off-by: Ajesh JS <ajesh.js@hp.com>
> Reviewed-by: Liverance Fletcher <fletch@hp.com>; Clemenceau, <Matthieu matthieu.clemenceau@hp.com>
> "-------------------------------------------------------------------------"
> diff -rup linux-3.13.6/fs/btrfs/ioctl.c linux-3.13.6_btrfs/fs/btrfs/ioctl.c
> --- linux-3.13.6/fs/btrfs/ioctl.c       2014-03-07 11:37:02.000000000 +0530
> +++ linux-3.13.6_btrfs/fs/btrfs/ioctl.c 2014-03-19 14:25:28.375139699 +0530
> @@ -1636,6 +1636,68 @@ out:
>         return ret;
>  }
>
> +static noinline int btrfs_ioctl_subvol_modify(struct file *file,
> +                                               void __user *arg)
> +{
> +       struct btrfs_ioctl_vol_args_v2 *vol_args;
> +       struct inode *inode = file_inode(file);
> +       struct btrfs_root *root = BTRFS_I(inode)->root;
> +       struct btrfs_trans_handle *trans;
> +       u64 root_flags;
> +       u64 flags;
> +       int ret = 0;
> +
> +       ret = mnt_want_write_file(file);
> +       if (ret)
> +               goto out;
> +
> +       if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {
> +               ret = -EINVAL;
> +               goto out_drop_write;
> +       }
> +       vol_args = memdup_user(arg, sizeof(*vol_args));
> +       if (IS_ERR(vol_args))
> +               goto out_drop_write;
> +       vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';
> +       flags = vol_args->flags;
> +       if (!inode_owner_or_capable(inode)) {
> +               ret = -EACCES;
> +               goto out_drop_write;
> +       }
> +
> +       down_write(&root->fs_info->subvol_sem);
> +       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);
> +               printk(KERN_INFO "Setting %s to ro\n", vol_args->name);
> +       } else {
> +               btrfs_set_root_flags(&root->root_item,
> +                                       root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
> +               printk(KERN_INFO "Setting %s to rw\n", vol_args->name);
> +       }
> +
> +       trans = btrfs_start_transaction(root, 1);
> +       if (IS_ERR(trans)) {
> +               ret = PTR_ERR(trans);
> +               goto out_reset;
> +       }
> +
> +       ret = btrfs_update_root(trans, root->fs_info->tree_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);
> +       up_write(&root->fs_info->subvol_sem);
> +out_drop_write:
> +       mnt_drop_write_file(file);
> +out:
> +       return ret;
> +}
> +
>  static noinline int btrfs_ioctl_subvol_getflags(struct file *file,
>                                                 void __user *arg)
>  {
> @@ -4509,6 +4571,8 @@ long btrfs_ioctl(struct file *file, unsi
>                 return btrfs_ioctl_snap_create(file, argp, 1);
>         case BTRFS_IOC_SUBVOL_CREATE_V2:
>                 return btrfs_ioctl_snap_create_v2(file, argp, 1);
> +       case BTRFS_IOC_SUBVOL_MODIFY:
> +               return btrfs_ioctl_subvol_modify(file, argp);
>         case BTRFS_IOC_SNAP_DESTROY:
>                 return btrfs_ioctl_snap_destroy(file, argp);
>         case BTRFS_IOC_SUBVOL_GETFLAGS:
> diff -rup linux-3.13.6/include/uapi/linux/btrfs.h linux-3.13.6_btrfs/include/uapi/linux/btrfs.h
> --- linux-3.13.6/include/uapi/linux/btrfs.h     2014-03-07 11:37:02.000000000 +0530
> +++ linux-3.13.6_btrfs/include/uapi/linux/btrfs.h       2014-03-19 15:34:30.648255239 +0530
> @@ -606,5 +606,7 @@ static inline char *btrfs_err_str(enum b
>                                     struct btrfs_ioctl_dev_replace_args)
>  #define BTRFS_IOC_FILE_EXTENT_SAME _IOWR(BTRFS_IOCTL_MAGIC, 54, \
>                                          struct btrfs_ioctl_same_args)
> +#define BTRFS_IOC_SUBVOL_MODIFY _IOW(BTRFS_IOCTL_MAGIC, 55, \
> +                                  struct btrfs_ioctl_vol_args_v2)
>
>  #endif /* _UAPI_LINUX_BTRFS_H */
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Patch
diff mbox

diff -rup linux-3.13.6/fs/btrfs/ioctl.c linux-3.13.6_btrfs/fs/btrfs/ioctl.c
--- linux-3.13.6/fs/btrfs/ioctl.c	2014-03-07 11:37:02.000000000 +0530
+++ linux-3.13.6_btrfs/fs/btrfs/ioctl.c	2014-03-19 14:25:28.375139699 +0530
@@ -1636,6 +1636,68 @@  out:
 	return ret;
 }
 
+static noinline int btrfs_ioctl_subvol_modify(struct file *file,
+						void __user *arg)
+{
+	struct btrfs_ioctl_vol_args_v2 *vol_args;
+	struct inode *inode = file_inode(file);
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_trans_handle *trans;
+	u64 root_flags;
+	u64 flags;
+	int ret = 0;
+
+	ret = mnt_want_write_file(file);
+	if (ret)
+		goto out;
+
+	if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {
+		ret = -EINVAL;
+		goto out_drop_write;
+	}
+	vol_args = memdup_user(arg, sizeof(*vol_args));
+	if (IS_ERR(vol_args))
+		goto out_drop_write;
+	vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';
+	flags = vol_args->flags;
+	if (!inode_owner_or_capable(inode)) {
+		ret = -EACCES;
+		goto out_drop_write;
+	}
+
+	down_write(&root->fs_info->subvol_sem);
+	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);
+		printk(KERN_INFO "Setting %s to ro\n", vol_args->name);
+	} else {
+		btrfs_set_root_flags(&root->root_item,
+					root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
+		printk(KERN_INFO "Setting %s to rw\n", vol_args->name);
+	}
+
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out_reset;
+	}
+
+	ret = btrfs_update_root(trans, root->fs_info->tree_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);
+	up_write(&root->fs_info->subvol_sem);
+out_drop_write:
+	mnt_drop_write_file(file);
+out:
+	return ret;
+}
+
 static noinline int btrfs_ioctl_subvol_getflags(struct file *file,
 						void __user *arg)
 {
@@ -4509,6 +4571,8 @@  long btrfs_ioctl(struct file *file, unsi
 		return btrfs_ioctl_snap_create(file, argp, 1);
 	case BTRFS_IOC_SUBVOL_CREATE_V2:
 		return btrfs_ioctl_snap_create_v2(file, argp, 1);
+	case BTRFS_IOC_SUBVOL_MODIFY:
+		return btrfs_ioctl_subvol_modify(file, argp);
 	case BTRFS_IOC_SNAP_DESTROY:
 		return btrfs_ioctl_snap_destroy(file, argp);
 	case BTRFS_IOC_SUBVOL_GETFLAGS:
diff -rup linux-3.13.6/include/uapi/linux/btrfs.h linux-3.13.6_btrfs/include/uapi/linux/btrfs.h
--- linux-3.13.6/include/uapi/linux/btrfs.h	2014-03-07 11:37:02.000000000 +0530
+++ linux-3.13.6_btrfs/include/uapi/linux/btrfs.h	2014-03-19 15:34:30.648255239 +0530
@@ -606,5 +606,7 @@  static inline char *btrfs_err_str(enum b
 				    struct btrfs_ioctl_dev_replace_args)
 #define BTRFS_IOC_FILE_EXTENT_SAME _IOWR(BTRFS_IOCTL_MAGIC, 54, \
 					 struct btrfs_ioctl_same_args)
+#define BTRFS_IOC_SUBVOL_MODIFY _IOW(BTRFS_IOCTL_MAGIC, 55, \
+				   struct btrfs_ioctl_vol_args_v2)
 
 #endif /* _UAPI_LINUX_BTRFS_H */