[PATCH RFC v2 07/28] vfs: make vfs_create break delegations on parent directory

Jeff Layton
2025-06-02T14:02:37Z

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.

Rename vfs_create as __vfs_create, make it static, and add a new
delegated_inode parameter. Fix do_mknodat to call __vfs_create and wait
for a delegation break if there is one. Add a new exported vfs_create
wrapper that passes in NULL for delegated_inode.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/namei.c | 55 ++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index c8fe924cbb7dcefac9a4930df9f8303d9a478508..7b27a9bc4616d3880d6365f1e37f13f7f45bc2c9 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3370,6 +3370,32 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
return mode;
}

+static int __vfs_create(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, umode_t mode, bool want_excl,
+ struct inode **delegated_inode)
+{
+ int error;
+
+ error = may_create(idmap, dir, dentry);
+ if (error)
+ return error;
+
+ if (!dir->i_op->create)
+ return -EACCES; /* shouldn't it be ENOSYS? */
+
+ mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
+ error = security_inode_create(dir, dentry, mode);
+ if (error)
+ return error;
+ error = try_break_deleg(dir, delegated_inode);
+ if (error)
+ return error;
+ error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
+ if (!error)
+ fsnotify_create(dir, dentry);
+ return error;
+}
+
/**
* vfs_create - create new file
* @idmap: idmap of the mount the inode was found from
@@ -3389,23 +3415,7 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
int vfs_create(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, bool want_excl)
{
- int error;
-
- error = may_create(idmap, dir, dentry);
- if (error)
- return error;
-
- if (!dir->i_op->create)
- return -EACCES; /* shouldn't it be ENOSYS? */
-
- mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
- error = security_inode_create(dir, dentry, mode);
- if (error)
- return error;
- error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
- if (!error)
- fsnotify_create(dir, dentry);
- return error;
+ return __vfs_create(idmap, dir, dentry, mode, want_excl, NULL);
}
EXPORT_SYMBOL(vfs_create);

@@ -4278,6 +4288,7 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
struct path path;
int error;
unsigned int lookup_flags = 0;
+ struct inode *delegated_inode = NULL;

error = may_mknod(mode);
if (error)
@@ -4296,8 +4307,9 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
idmap = mnt_idmap(path.mnt);
switch (mode & S_IFMT) {
case 0: case S_IFREG:
- error = vfs_create(idmap, path.dentry->d_inode,
- dentry, mode, true);
+ error = __vfs_create(idmap, path.dentry->d_inode,
+ dentry, mode, true,
+ &delegated_inode);
if (!error)
security_path_post_mknod(idmap, dentry);
break;
@@ -4312,6 +4324,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
}
out2:
done_path_create(&path, dentry);
+ if (delegated_inode) {
+ error = break_deleg_wait(&delegated_inode);
+ if (!error)
+ goto retry;
+ }
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;

--
2.49.0