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Message-ID: <1C24A869E87C7B45BE3E2BB439AB8F8C0D13DAE0@G5W2738.americas.hpqcorp.net>
Date: Wed, 23 Apr 2014 13:28:01 +0000
From: "J S, Ajesh" <ajesh.js@...com>
To: "clm@...com" <clm@...com>, "jbacik@...com" <jbacik@...com>
CC: "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 001/001] btrfs: Mechanism to modify the permission of a
subvolume
From: Ajesh JS <ajesh.js@...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@...com>
Reviewed-by: Liverance Fletcher <fletch@...com>; Clemenceau, <Matthieu matthieu.clemenceau@...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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