fs: add i_user_ns() helper

commit a1ec9040a2a9122605ac26e5725c6de019184419 upstream.

Since we'll be passing the filesystem's idmapping in even more places in
the following patches and we do already dereference struct inode to get
to the filesystem's idmapping multiple times add a tiny helper.

Link: https://lore.kernel.org/r/20211123114227.3124056-10-brauner@kernel.org
Link: https://lore.kernel.org/r/20211130121032.3753852-10-brauner@kernel.org
Link: https://lore.kernel.org/r/20211203111707.3901969-10-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f62c1b9cd7cded56d3f9c9a1c8436c0e1e583ed0..d418dffb1681833bafce6a173fad8d9300c947f6 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1602,6 +1602,11 @@ struct super_block {
        struct list_head        s_inodes_wb;    /* writeback inodes */
 } __randomize_layout;
 
+static inline struct user_namespace *i_user_ns(const struct inode *inode)
+{
+       return inode->i_sb->s_user_ns;
+}
+
 /* Helper functions so that in most cases filesystems will
  * not need to deal directly with kuid_t and kgid_t and can
  * instead deal with the raw numeric values that are stored
@@ -1609,22 +1614,22 @@ struct super_block {
  */
 static inline uid_t i_uid_read(const struct inode *inode)
 {
-       return from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
+       return from_kuid(i_user_ns(inode), inode->i_uid);
 }
 
 static inline gid_t i_gid_read(const struct inode *inode)
 {
-       return from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
+       return from_kgid(i_user_ns(inode), inode->i_gid);
 }
 
 static inline void i_uid_write(struct inode *inode, uid_t uid)
 {
-       inode->i_uid = make_kuid(inode->i_sb->s_user_ns, uid);
+       inode->i_uid = make_kuid(i_user_ns(inode), uid);
 }
 
 static inline void i_gid_write(struct inode *inode, gid_t gid)
 {
-       inode->i_gid = make_kgid(inode->i_sb->s_user_ns, gid);
+       inode->i_gid = make_kgid(i_user_ns(inode), gid);
 }
 
 /**