On Fri, Sep 29, 2017 at 10:15:30PM +0300, Nikolay Borisov wrote:
> > Adding the transaction before the "if (flags & BTRFS_SUBVOL_RDONLY)"
> > condition makes it much worse. The "is subvolume in send" test is
> > supposed to be lightweight and should not shoot down the whole
> > filesystem. The usecase is explained in 2c68653787f91c62f8.
> >
> > Also the received_uuid must be changed under the root_item_lock.
> >
> > I think it should be fine to keep the transaction start where it is,
> > change the received_uuid eventually and let it commit. You can set the
> > transaction units to 2 unconditionally.
>
> So what you are suggesting is to not move the transaction start before
> the if check? But then how would you structure the code to remove the
> uuid only if we are switchin RO->RW and not in send without duplicating
> the checks right before btrfs_update_root?
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1772,6 +1772,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct
file *file,
u64 root_flags;
u64 flags;
int ret = 0;
+ bool clear_received_uuid = false;
if (!inode_owner_or_capable(inode))
return -EPERM;
@@ -1820,6 +1821,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct
file *file,
btrfs_set_root_flags(&root->root_item,
root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
spin_unlock(&root->root_item_lock);
+ clear_received_uuid = true;
} else {
spin_unlock(&root->root_item_lock);
btrfs_warn(fs_info,
@@ -1836,6 +1838,24 @@ static noinline int btrfs_ioctl_subvol_setflags(struct
file *file,
goto out_reset;
}
+ if (clear_received_uuid) {
+ if (!btrfs_is_empty_uuid(root->root_item.received_uuid)) {
+ ret = btrfs_uuid_tree_rem(trans, fs_info,
+ root->root_item.received_uuid,
+ BTRFS_UUID_KEY_RECEIVED_SUBVOL,
+ root->root_key.objectid);
+
+ if (ret && ret != -ENOENT) {
+ btrfs_abort_transaction(trans, ret);
+ btrfs_end_transaction(trans);
+ goto out_reset;
+ }
+
+ memset(root->root_item.received_uuid, 0,
+ BTRFS_UUID_SIZE);
+ }
+ }
+
ret = btrfs_update_root(trans, fs_info->tree_root,
&root->root_key, &root->root_item);
--
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