* [RFC] Removing a subvolume by an ordinary user
@ 2010-09-16 11:47 kreijack
2010-09-18 13:15 ` Goffredo Baroncelli
0 siblings, 1 reply; 2+ messages in thread
From: kreijack @ 2010-09-16 11:47 UTC (permalink / raw)
To: linux-btrfs
Hi all,
currently BTRFS doesn't allow an ordinary user to remove a subvolume (o=
r=20
snapshot). I think that the reasons is simple: a subvolume may contain=20
files/directories owned by other user.
Allowing an ordinary user to remove a subvolume means allowing an ordin=
ary=20
user to remove filess/directories owned by other user. And this is not =
good.
Moreover BTRFS removes a subvolume asynchronously, so it is not possib=
le to=20
return an error like =E2=80=9Chey you are trying to remove a not your f=
ile ! Don=E2=80=99t do=20
it !=E2=80=9D.
My idea is to add another ioctl that permits to remove a subvolume only=
when=20
it is empty and its host directory is writable by the user=E2=80=A6 lik=
e a directory.=20
An option is to allow to remove an empty subvolume with the unlink(2) =
syscall:=20
no more tool is needed !=20
This will solve a lot of problem:
- Consistently with the current unlink(2) behavior
- The kernel has not to do complicate check
- There no is necessity to add another interface to wait the releasing =
of the=20
space (see other thread reserving an IOCTL number; other details ).
The disadvantage is that it should be slower than the currently=20
implementation.
Of course I don=E2=80=99t want to remove the existing interface. I want=
only to add=20
another one.
Comments ? Thoughts ?
Regards
G.Baroncelli=20
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [RFC] Removing a subvolume by an ordinary user
2010-09-16 11:47 [RFC] Removing a subvolume by an ordinary user kreijack
@ 2010-09-18 13:15 ` Goffredo Baroncelli
0 siblings, 0 replies; 2+ messages in thread
From: Goffredo Baroncelli @ 2010-09-18 13:15 UTC (permalink / raw)
To: linux-btrfs
[-- Attachment #1: Type: Text/Plain, Size: 3891 bytes --]
Hi all,
enclosed you can find a patch which permits to remove a volume via the
rmdir(2) syscall by an ordinary user.
The rules for a subvolume removal are the same ones of a directory:
- the user shall have the write permission on the parent directory
- the subvolume shall be empty
Comments are welcome
Reagrds
G.Baroncelli
NB: this is code is not fully tested, handle with care.
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f08427c..47d11d8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2944,6 +2944,86 @@ int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
return 0;
}
+int may_destroy_subvol(struct btrfs_root *root);
+static noinline int btrfs_snap_destroy(struct inode *dir,
+ struct dentry *dentry)
+
+{
+
+ struct inode *inode;
+ struct btrfs_root *root = BTRFS_I(dir)->root;
+ struct btrfs_root *dest = NULL;
+ struct btrfs_trans_handle *trans;
+
+ int ret;
+ int err = 0;
+
+
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ goto out;
+ }
+
+ if (!dentry->d_inode) {
+ err = -ENOENT;
+ goto out;
+ }
+
+ inode = dentry->d_inode;
+ if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ dest = BTRFS_I(inode)->root;
+
+ down_write(&root->fs_info->subvol_sem);
+
+ err = may_destroy_subvol(dest);
+ if (err)
+ goto out_up_write;
+
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans)) {
+ err = PTR_ERR(trans);
+ goto out_up_write;
+ }
+ trans->block_rsv = &root->fs_info->global_block_rsv;
+
+ ret = btrfs_unlink_subvol(trans, root, dir,
+ dest->root_key.objectid,
+ dentry->d_name.name,
+ dentry->d_name.len);
+ BUG_ON(ret);
+
+ btrfs_record_root_in_trans(trans, dest);
+
+ memset(&dest->root_item.drop_progress, 0,
+ sizeof(dest->root_item.drop_progress));
+ dest->root_item.drop_level = 0;
+ btrfs_set_root_refs(&dest->root_item, 0);
+
+ if (!xchg(&dest->orphan_item_inserted, 1)) {
+ ret = btrfs_insert_orphan_item(trans,
+ root->fs_info->tree_root,
+ dest->root_key.objectid);
+ BUG_ON(ret);
+ }
+
+ ret = btrfs_commit_transaction(trans, root);
+ BUG_ON(ret);
+ inode->i_flags |= S_DEAD;
+out_up_write:
+ up_write(&root->fs_info->subvol_sem);
+ if (!err) {
+ shrink_dcache_sb(root->fs_info->sb);
+ btrfs_invalidate_inodes(dest);
+ /*d_delete(dentry);*/
+ }
+out:
+ return err;
+}
+
static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
@@ -2952,10 +3032,12 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
struct btrfs_trans_handle *trans;
unsigned long nr = 0;
- if (inode->i_size > BTRFS_EMPTY_DIR_SIZE ||
- inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
+ if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
return -ENOTEMPTY;
+ if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
+ return btrfs_snap_destroy(dir, dentry);
+
trans = __unlink_start_trans(dir, dentry);
if (IS_ERR(trans))
return PTR_ERR(trans);
@@ -4242,7 +4324,6 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
over = filldir(dirent, name_ptr, name_len,
found_key.offset, location.objectid,
d_type);
-
skip:
if (name_ptr != tmp_name)
kfree(name_ptr);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9254b3d..a7b242e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -855,7 +855,7 @@ out:
/*
* helper to check if the subvolume references other subvolumes
*/
-static noinline int may_destroy_subvol(struct btrfs_root *root)
+int may_destroy_subvol(struct btrfs_root *root)
{
struct btrfs_path *path;
struct btrfs_key key;
--
gpg key@ keyserver.linux.it: Goffredo Baroncelli (ghigo) <kreijackATinwind.it>
Key fingerprint = 4769 7E51 5293 D36C 814E C054 BF04 F161 3DC5 0512
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2010-09-18 13:15 ` Goffredo Baroncelli
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