vfs: break parent dir delegations in open(..., O_CREAT) codepath

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>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-8-52f3feebb2f2@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/namei.c b/fs/namei.c
index 9e0393a92091ac522b5324fcdad8c5592a948e8d..f439429bdfa271ccc64c937771ef4175597feb53 100644 (file)
--- 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);