fs: port i_{g,u}id_into_vfs{g,u}id() to const mnt_idmap

Convert to const struct mnt_idmap.

A mount's idmapping is immutable. The only thing that is allowed to be
modified afterwards is the reference count and that is hidden behind
mnt_idmap_get() and mnt_idmap_put(). Everything else only ever reads
from the idmapping. This is the same model that struct cred uses and the
idmapping is also rather sensitive.

So make the idmap argument const wherever we can. The conversion is done
from the bottom up so callers can continue to pass a non-const pointer
to a const parameter until the conversion is finished.

No functional changes.

Link: https://patch.msgid.link/20260901-work-idmap-const-v1-5-54ccd48e100b@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Seth Forshee <sforshee@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 959c747ef75a..cec5de83d882 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1439,7 +1439,7 @@ static inline void i_gid_write(struct inode *inode, gid_t gid)
  * Return: whe inode's i_uid mapped down according to @idmap.
  * If the inode's i_uid has no mapping INVALID_VFSUID is returned.
  */
-static inline vfsuid_t i_uid_into_vfsuid(struct mnt_idmap *idmap,
+static inline vfsuid_t i_uid_into_vfsuid(const struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
 	return make_vfsuid(idmap, i_user_ns(inode), inode->i_uid);
@@ -1491,7 +1491,7 @@ static inline void i_uid_update(struct mnt_idmap *idmap,
  * Return: the inode's i_gid mapped down according to @idmap.
  * If the inode's i_gid has no mapping INVALID_VFSGID is returned.
  */
-static inline vfsgid_t i_gid_into_vfsgid(struct mnt_idmap *idmap,
+static inline vfsgid_t i_gid_into_vfsgid(const struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
 	return make_vfsgid(idmap, i_user_ns(inode), inode->i_gid);
@@ -2173,7 +2173,7 @@ extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
 				 (inode)->i_rdev == WHITEOUT_DEV)
 #define IS_ANON_FILE(inode)	((inode)->i_flags & S_ANON_INODE)
 
-static inline bool HAS_UNMAPPED_ID(struct mnt_idmap *idmap,
+static inline bool HAS_UNMAPPED_ID(const struct mnt_idmap *idmap,
 				   struct inode *inode)
 {
 	return !vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||