Hi all,
when creating a new snapshot or subvolume we need to drop an existing
negative dentry for the new name, else this happens:
host ~ # ls -l /mnt/btrfs
total 1
dr-xr-xr-x 1 root root 0 Jan 1 1970 default
host ~ # stat /mnt/btrfs/snapshot
stat: cannot stat `/mnt/btrfs/snapshot': No such file or directory
host ~ # btrfsctl -s snapshot /mnt/btrfs/default
ioctl returns 0
host ~ # stat /mnt/btrfs/snapshot
stat: cannot stat `/mnt/btrfs/snapshot': No such file or directory
host ~ # ls -l /mnt/btrfs
ls: cannot access /mnt/btrfs/snapshot: No such file or directory
total 1
dr-xr-xr-x 1 root root 0 Jan 1 1970 default
d????????? ? ? ? ? ? snapshot
I have a patch (see below) that does an explicit d_drop() on the dentry
after looking it up via d_find_alias() and d_lookup(), starting at the
root inode. Currently it's for snapshot creation only, subvolume creation
needs the same. There doesn't seem to be a kernel function for this case
and using the normal d_revalidate method is inefficient as snapshot and
subvolume creation is the only place where we need this and the creation
is a rare case. Is this the right way to go?
Sven
---
transaction.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/transaction.c
+++ b/transaction.c
@@ -557,6 +557,8 @@
struct btrfs_root *tree_root = fs_info->tree_root;
struct btrfs_root *root = pending->root;
struct extent_buffer *tmp;
+ struct dentry *alias, *snap;
+ struct qstr qstr;
int ret;
u64 objectid;
@@ -604,6 +606,22 @@
ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
pending->name, strlen(pending->name), objectid,
root->fs_info->sb->s_root->d_inode->i_ino);
+
+ /*
+ * We need to drop the dcache entry for the new snapshot.
+ */
+ alias = d_find_alias(root->fs_info->sb->s_root->d_inode);
+ if (alias) {
+ qstr.name = pending->name;
+ qstr.len = strlen(qstr.name);
+ qstr.hash = full_name_hash(qstr.name, qstr.len);
+ snap = d_lookup(alias, &qstr);
+ dput(alias);
+ if (snap) {
+ d_drop(snap);
+ dput(snap);
+ }
+ }
fail:
kfree(new_root_item);
return ret;
--
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