[PATCH RFC v2 06/28] vfs: break parent dir delegations in open(..., O_CREAT) codepath

Jeff Layton
2025-06-02T14:02:34Z

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.

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 2211ed9f427cc97391d068b1a33ce388266a3e02..c8fe924cbb7dcefac9a4930df9f8303d9a478508 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3609,7 +3609,7 @@ 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 inode **delegated_inode)
{
struct mnt_idmap *idmap;
struct dentry *dir = nd->path.dentry;
@@ -3698,6 +3698,11 @@ 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) {
@@ -3761,6 +3766,7 @@ static const char *open_last_lookups(struct nameidata *nd,
struct file *file, const struct open_flags *op)
{
struct dentry *dir = nd->path.dentry;
+ struct inode *delegated_inode = NULL;
int open_flag = op->open_flag;
bool got_write = false;
struct dentry *dentry;
@@ -3791,7 +3797,7 @@ 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);
/*
@@ -3804,7 +3810,7 @@ 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);
@@ -3819,8 +3825,16 @@ 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 (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);

--
2.49.0