config fs: avoid switching ->d_op on live dentry
Switching d_op on a live dentry is racy in general, so avoid it. In this case
it is a negative dentry, which is safer, but there are still concurrent ops
which may be called on d_op in that case (eg. d_revalidate). So in general
a filesystem may not do this. Fix configfs so as not to do this.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 0b502f8..5787069 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -232,10 +232,8 @@
sd->s_mode = mode;
sd->s_dentry = dentry;
- if (dentry) {
+ if (dentry)
dentry->d_fsdata = configfs_get(sd);
- dentry->d_op = &configfs_dentry_ops;
- }
return 0;
}
@@ -278,7 +276,6 @@
error = configfs_create(d, mode, init_dir);
if (!error) {
inc_nlink(p->d_inode);
- (d)->d_op = &configfs_dentry_ops;
} else {
struct configfs_dirent *sd = d->d_fsdata;
if (sd) {
@@ -371,9 +368,7 @@
CONFIGFS_ITEM_LINK);
if (!err) {
err = configfs_create(dentry, mode, init_symlink);
- if (!err)
- dentry->d_op = &configfs_dentry_ops;
- else {
+ if (err) {
struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
spin_lock(&configfs_dirent_lock);
@@ -493,7 +488,11 @@
* If it doesn't exist and it isn't a NOT_PINNED item,
* it must be negative.
*/
- return simple_lookup(dir, dentry, nd);
+ if (dentry->d_name.len > NAME_MAX)
+ return ERR_PTR(-ENAMETOOLONG);
+ dentry->d_op = &configfs_dentry_ops;
+ d_add(dentry, NULL);
+ return NULL;
}
out:
@@ -685,6 +684,7 @@
ret = -ENOMEM;
child = d_alloc(parent, &name);
if (child) {
+ child->d_op = &configfs_dentry_ops;
d_add(child, NULL);
ret = configfs_attach_group(&parent_group->cg_item,
@@ -1682,6 +1682,7 @@
err = -ENOMEM;
dentry = d_alloc(configfs_sb->s_root, &name);
if (dentry) {
+ dentry->d_op = &configfs_dentry_ops;
d_add(dentry, NULL);
err = configfs_attach_group(sd->s_element, &group->cg_item,
