fs: port fs{g,u}id helpers to mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("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>

4 files changed, 10 insertions, 17 deletions

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 1024b0c02431..157663031f8c 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -943,7 +943,6 @@ struct inode *__ext4_new_inode(struct mnt_idmap *idmap,
 	ext4_group_t flex_group;
 	struct ext4_group_info *grp = NULL;
 	bool encrypt = false;
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	/* Cannot create files in a deleted directory */
 	if (!dir || !dir->i_nlink)
@@ -973,7 +972,7 @@ struct inode *__ext4_new_inode(struct mnt_idmap *idmap,
 		i_gid_write(inode, owner[1]);
 	} else if (test_opt(sb, GRPID)) {
 		inode->i_mode = mode;
-		inode_fsuid_set(inode, mnt_userns);
+		inode_fsuid_set(inode, idmap);
 		inode->i_gid = dir->i_gid;
 	} else
 		inode_init_owner(idmap, inode, dir, mode);
diff --git a/fs/inode.c b/fs/inode.c
index 1aec92141fab..1b05e0e4b5c8 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2293,9 +2293,7 @@ EXPORT_SYMBOL(init_special_inode);
 void inode_init_owner(struct mnt_idmap *idmap, struct inode *inode,
 		      const struct inode *dir, umode_t mode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
-	inode_fsuid_set(inode, mnt_userns);
+	inode_fsuid_set(inode, idmap);
 	if (dir && dir->i_mode & S_ISGID) {
 		inode->i_gid = dir->i_gid;
 
@@ -2303,7 +2301,7 @@ void inode_init_owner(struct mnt_idmap *idmap, struct inode *inode,
 		if (S_ISDIR(mode))
 			mode |= S_ISGID;
 	} else
-		inode_fsgid_set(inode, mnt_userns);
+		inode_fsgid_set(inode, idmap);
 	inode->i_mode = mode;
 }
 EXPORT_SYMBOL(inode_init_owner);
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 59fb064e2df3..7f1d715faab5 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -788,7 +788,6 @@ xfs_init_new_inode(
 	bool			init_xattrs,
 	struct xfs_inode	**ipp)
 {
-	struct user_namespace	*mnt_userns = mnt_idmap_owner(idmap);
 	struct inode		*dir = pip ? VFS_I(pip) : NULL;
 	struct xfs_mount	*mp = tp->t_mountp;
 	struct xfs_inode	*ip;
@@ -824,7 +823,7 @@ xfs_init_new_inode(
 	ip->i_projid = prid;
 
 	if (dir && !(dir->i_mode & S_ISGID) && xfs_has_grpid(mp)) {
-		inode_fsuid_set(inode, mnt_userns);
+		inode_fsuid_set(inode, idmap);
 		inode->i_gid = dir->i_gid;
 		inode->i_mode = mode;
 	} else {
@@ -955,7 +954,6 @@ xfs_create(
 	bool			init_xattrs,
 	xfs_inode_t		**ipp)
 {
-	struct user_namespace	*mnt_userns = mnt_idmap_owner(idmap);
 	int			is_dir = S_ISDIR(mode);
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_inode	*ip = NULL;
@@ -980,8 +978,8 @@ xfs_create(
 	/*
 	 * Make sure that we have allocated dquot(s) on disk.
 	 */
-	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
-			mapped_fsgid(mnt_userns, &init_user_ns), prid,
+	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns),
+			mapped_fsgid(idmap, &init_user_ns), prid,
 			XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 			&udqp, &gdqp, &pdqp);
 	if (error)
@@ -1109,7 +1107,6 @@ xfs_create_tmpfile(
 	umode_t			mode,
 	struct xfs_inode	**ipp)
 {
-	struct user_namespace	*mnt_userns = mnt_idmap_owner(idmap);
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_inode	*ip = NULL;
 	struct xfs_trans	*tp = NULL;
@@ -1130,8 +1127,8 @@ xfs_create_tmpfile(
 	/*
 	 * Make sure that we have allocated dquot(s) on disk.
 	 */
-	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
-			mapped_fsgid(mnt_userns, &init_user_ns), prid,
+	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns),
+			mapped_fsgid(idmap, &init_user_ns), prid,
 			XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 			&udqp, &gdqp, &pdqp);
 	if (error)
diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c
index 24cf0a16bf35..85e433df6a3f 100644
--- a/fs/xfs/xfs_symlink.c
+++ b/fs/xfs/xfs_symlink.c
@@ -151,7 +151,6 @@ xfs_symlink(
 	umode_t			mode,
 	struct xfs_inode	**ipp)
 {
-	struct user_namespace	*mnt_userns = mnt_idmap_owner(idmap);
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_trans	*tp = NULL;
 	struct xfs_inode	*ip = NULL;
@@ -194,8 +193,8 @@ xfs_symlink(
 	/*
 	 * Make sure that we have allocated dquot(s) on disk.
 	 */
-	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
-			mapped_fsgid(mnt_userns, &init_user_ns), prid,
+	error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns),
+			mapped_fsgid(idmap, &init_user_ns), prid,
 			XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 			&udqp, &gdqp, &pdqp);
 	if (error)