fs: port ->symlink() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

Documentation/filesystems/locking.rst

@@ -60,7 +60,7 @@ prototypes::
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 	int (*link) (struct dentry *,struct inode *,struct dentry *);
 	int (*unlink) (struct inode *,struct dentry *);
-	int (*symlink) (struct inode *,struct dentry *,const char *);
+	int (*symlink) (struct mnt_idmap *, struct inode *,struct dentry *,const char *);
 	int (*mkdir) (struct inode *,struct dentry *,umode_t);
 	int (*rmdir) (struct inode *,struct dentry *);
 	int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);

Documentation/filesystems/vfs.rst

@@ -425,7 +425,7 @@ As of kernel 2.6.22, the following members are defined:
 		struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 		int (*link) (struct dentry *,struct inode *,struct dentry *);
 		int (*unlink) (struct inode *,struct dentry *);
-		int (*symlink) (struct user_namespace *, struct inode *,struct dentry *,const char *);
+		int (*symlink) (struct mnt_idmap *, struct inode *,struct dentry *,const char *);
 		int (*mkdir) (struct user_namespace *, struct inode *,struct dentry *,umode_t);
 		int (*rmdir) (struct inode *,struct dentry *);
 		int (*mknod) (struct user_namespace *, struct inode *,struct dentry *,umode_t,dev_t);

fs/9p/vfs_inode.c

@@ -1300,7 +1300,7 @@ static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
 
 /**
  * v9fs_vfs_symlink - helper function to create symlinks
- * @mnt_userns: The user namespace of the mount
+ * @idmap: idmap of the mount
  * @dir: directory inode containing symlink
  * @dentry: dentry for symlink
  * @symname: symlink data
@@ -1310,7 +1310,7 @@ static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
  */
 
 static int
-v9fs_vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+v9fs_vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		 struct dentry *dentry, const char *symname)
 {
 	p9_debug(P9_DEBUG_VFS, " %lu,%pd,%s\n",

fs/9p/vfs_inode_dotl.c

@@ -688,7 +688,7 @@ v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode,
 }
 
 static int
-v9fs_vfs_symlink_dotl(struct user_namespace *mnt_userns, struct inode *dir,
+v9fs_vfs_symlink_dotl(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *dentry, const char *symname)
 {
 	int err;

fs/affs/affs.h

@@ -174,7 +174,7 @@ extern int	affs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 extern int	affs_rmdir(struct inode *dir, struct dentry *dentry);
 extern int	affs_link(struct dentry *olddentry, struct inode *dir,
 			  struct dentry *dentry);
-extern int	affs_symlink(struct user_namespace *mnt_userns,
+extern int	affs_symlink(struct mnt_idmap *idmap,
 			struct inode *dir, struct dentry *dentry,
 			const char *symname);
 extern int	affs_rename2(struct user_namespace *mnt_userns,

fs/affs/namei.c

@@ -313,7 +313,7 @@ affs_rmdir(struct inode *dir, struct dentry *dentry)
 }
 
 int
-affs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+affs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	     struct dentry *dentry, const char *symname)
 {
 	struct super_block	*sb = dir->i_sb;

fs/afs/dir.c

@@ -36,7 +36,7 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry);
 static int afs_unlink(struct inode *dir, struct dentry *dentry);
 static int afs_link(struct dentry *from, struct inode *dir,
 		    struct dentry *dentry);
-static int afs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int afs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, const char *content);
 static int afs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 		      struct dentry *old_dentry, struct inode *new_dir,
@@ -1760,7 +1760,7 @@ static const struct afs_operation_ops afs_symlink_operation = {
 /*
  * create a symlink in an AFS filesystem
  */
-static int afs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int afs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, const char *content)
 {
 	struct afs_operation *op;

fs/autofs/root.c

@@ -11,7 +11,7 @@
 #include "autofs_i.h"
 
 static int autofs_dir_permission(struct user_namespace *, struct inode *, int);
-static int autofs_dir_symlink(struct user_namespace *, struct inode *,
+static int autofs_dir_symlink(struct mnt_idmap *, struct inode *,
 			      struct dentry *, const char *);
 static int autofs_dir_unlink(struct inode *, struct dentry *);
 static int autofs_dir_rmdir(struct inode *, struct dentry *);
@@ -563,7 +563,7 @@ static int autofs_dir_permission(struct user_namespace *mnt_userns,
 	return generic_permission(mnt_userns, inode, mask);
 }
 
-static int autofs_dir_symlink(struct user_namespace *mnt_userns,
+static int autofs_dir_symlink(struct mnt_idmap *idmap,
 			      struct inode *dir, struct dentry *dentry,
 			      const char *symname)
 {

fs/bad_inode.c

@@ -51,7 +51,7 @@ static int bad_inode_unlink(struct inode *dir, struct dentry *dentry)
 	return -EIO;
 }
 
-static int bad_inode_symlink(struct user_namespace *mnt_userns,
+static int bad_inode_symlink(struct mnt_idmap *idmap,
 			     struct inode *dir, struct dentry *dentry,
 			     const char *symname)
 {

fs/btrfs/inode.c

@@ -9758,9 +9758,10 @@ out:
 	return ret;
 }
 
-static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int btrfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			 struct dentry *dentry, const char *symname)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;

fs/ceph/dir.c

@@ -912,7 +912,7 @@ static int ceph_create(struct mnt_idmap *idmap, struct inode *dir,
 	return ceph_mknod(mnt_userns, dir, dentry, mode, 0);
 }
 
-static int ceph_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int ceph_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *dentry, const char *dest)
 {
 	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

fs/cifs/cifsfs.h

@@ -124,7 +124,7 @@ extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
 /* Functions related to symlinks */
 extern const char *cifs_get_link(struct dentry *, struct inode *,
 			struct delayed_call *);
-extern int cifs_symlink(struct user_namespace *mnt_userns, struct inode *inode,
+extern int cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
 			struct dentry *direntry, const char *symname);
 
 #ifdef CONFIG_CIFS_XATTR

fs/cifs/link.c

@@ -568,7 +568,7 @@ cifs_hl_exit:
 }
 
 int
-cifs_symlink(struct user_namespace *mnt_userns, struct inode *inode,
+cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
 	     struct dentry *direntry, const char *symname)
 {
 	int rc = -EOPNOTSUPP;

fs/coda/dir.c

@@ -228,7 +228,7 @@ static int coda_link(struct dentry *source_de, struct inode *dir_inode,
 }
 
 
-static int coda_symlink(struct user_namespace *mnt_userns,
+static int coda_symlink(struct mnt_idmap *idmap,
 			struct inode *dir_inode, struct dentry *de,
 			const char *symname)
 {

fs/configfs/configfs_internal.h

@@ -91,7 +91,7 @@ extern const struct inode_operations configfs_root_inode_operations;
 extern const struct inode_operations configfs_symlink_inode_operations;
 extern const struct dentry_operations configfs_dentry_ops;
 
-extern int configfs_symlink(struct user_namespace *mnt_userns,
+extern int configfs_symlink(struct mnt_idmap *idmap,
 			    struct inode *dir, struct dentry *dentry,
 			    const char *symname);
 extern int configfs_unlink(struct inode *dir, struct dentry *dentry);

fs/configfs/symlink.c

@@ -137,7 +137,7 @@ static int get_target(const char *symname, struct path *path,
 }
 
 
-int configfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		     struct dentry *dentry, const char *symname)
 {
 	int ret;

fs/ecryptfs/inode.c

@@ -456,7 +456,7 @@ static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry)
 	return ecryptfs_do_unlink(dir, dentry, d_inode(dentry));
 }
 
-static int ecryptfs_symlink(struct user_namespace *mnt_userns,
+static int ecryptfs_symlink(struct mnt_idmap *idmap,
 			    struct inode *dir, struct dentry *dentry,
 			    const char *symname)
 {

fs/ext2/namei.c

@@ -154,7 +154,7 @@ static int ext2_mknod (struct user_namespace * mnt_userns, struct inode * dir,
 	return err;
 }
 
-static int ext2_symlink (struct user_namespace * mnt_userns, struct inode * dir,
+static int ext2_symlink (struct mnt_idmap * idmap, struct inode * dir,
 	struct dentry * dentry, const char * symname)
 {
 	struct super_block * sb = dir->i_sb;

fs/ext4/namei.c

@@ -3340,9 +3340,10 @@ out:
 	return err;
 }
 
-static int ext4_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int ext4_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *dentry, const char *symname)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	handle_t *handle;
 	struct inode *inode;
 	int err, len = strlen(symname);

fs/f2fs/namei.c

@@ -660,9 +660,10 @@ static const char *f2fs_get_link(struct dentry *dentry,
 	return link;
 }
 
-static int f2fs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int f2fs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *dentry, const char *symname)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(dir);
 	struct inode *inode;
 	size_t len = strlen(symname);