[PATCH v6 08/17] vfs: break parent dir delegations in open(..., O_CREAT) codepath

Jeff Layton
2025-11-11T14:13:31Z

In order to add directory delegation support, we need to break
delegations on the parent whenever there is going to be a change in the
directory.

Add a delegated_inode parameter to lookup_open and have it break the
delegation. Then, open_last_lookups can wait for the delegation break
and retry the call to lookup_open once it's done.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/namei.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 9e0393a92091ac522b5324fcdad8c5592a948e8d..f439429bdfa271ccc64c937771ef4175597feb53 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3697,7 +3697,7 @@ static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
*/
static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
const struct open_flags *op,
- bool got_write)
+ bool got_write, struct delegated_inode *delegated_inode)
{
struct mnt_idmap *idmap;
struct dentry *dir = nd->path.dentry;
@@ -3786,6 +3786,11 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,

/* Negative dentry, just create the file */
if (!dentry->d_inode && (open_flag & O_CREAT)) {
+ /* but break the directory lease first! */
+ error = try_break_deleg(dir_inode, delegated_inode);
+ if (error)
+ goto out_dput;
+
file->f_mode |= FMODE_CREATED;
audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
if (!dir_inode->i_op->create) {
@@ -3848,6 +3853,7 @@ static struct dentry *lookup_fast_for_open(struct nameidata *nd, int open_flag)
static const char *open_last_lookups(struct nameidata *nd,
struct file *file, const struct open_flags *op)
{
+ struct delegated_inode delegated_inode = { };
struct dentry *dir = nd->path.dentry;
int open_flag = op->open_flag;
bool got_write = false;
@@ -3879,7 +3885,7 @@ static const char *open_last_lookups(struct nameidata *nd,
return ERR_PTR(-ECHILD);
}
}
-
+retry:
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
got_write = !mnt_want_write(nd->path.mnt);
/*
@@ -3892,7 +3898,7 @@ static const char *open_last_lookups(struct nameidata *nd,
inode_lock(dir->d_inode);
else
inode_lock_shared(dir->d_inode);
- dentry = lookup_open(nd, file, op, got_write);
+ dentry = lookup_open(nd, file, op, got_write, &delegated_inode);
if (!IS_ERR(dentry)) {
if (file->f_mode & FMODE_CREATED)
fsnotify_create(dir->d_inode, dentry);
@@ -3907,8 +3913,16 @@ static const char *open_last_lookups(struct nameidata *nd,
if (got_write)
mnt_drop_write(nd->path.mnt);

- if (IS_ERR(dentry))
+ if (IS_ERR(dentry)) {
+ if (is_delegated(&delegated_inode)) {
+ int error = break_deleg_wait(&delegated_inode);
+
+ if (!error)
+ goto retry;
+ return ERR_PTR(error);
+ }
return ERR_CAST(dentry);
+ }

if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
dput(nd->path.dentry);

--
2.51.1