Linux 4.8 compat: new s_user_ns member of struct super_block

Kernel 4.8 paved the way to enabling mounting a file system inside a
non-init user namespace. To facilitate this a s_user_ns member was
added holding the userns in which the filesystem's instance was
mounted. This enables doing the uid/gid translation relative to
this particular username space and not the default init_user_ns.

Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4928

diff --git a/config/kernel-super-userns.m4 b/config/kernel-super-userns.m4
new file mode 100644 (file)
index 0000000..de94ad9
--- /dev/null
+++ b/config/kernel-super-userns.m4
@@ -0,0 +1,21 @@
+dnl #
+dnl # 4.8 API change
+dnl # struct user_namespace was added to struct super_block as
+dnl # super->s_user_ns member
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SUPER_USER_NS], [
+       AC_MSG_CHECKING([whether super_block->s_user_ns exists])
+       ZFS_LINUX_TRY_COMPILE([
+               #include <linux/fs.h>
+               #include <linux/user_namespace.h>
+       ],[
+               struct super_block super;
+               super.s_user_ns = (struct user_namespace *)NULL;
+       ],[
+               AC_MSG_RESULT(yes)
+               AC_DEFINE(HAVE_SUPER_USER_NS, 1,
+                   [super_block->s_user_ns exists])
+       ],[
+               AC_MSG_RESULT(no)
+       ])
+])

diff --git a/config/kernel.m4 b/config/kernel.m4
index 7edafee0fc2096c7ee1533fe0fb8bf9b53cd8dd4..2fa04706b456fb53c3e4fcd7a2f428b3bd116064 100644 (file)
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -8,6 +8,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
        ZFS_AC_KERNEL_CONFIG
        ZFS_AC_KERNEL_DECLARE_EVENT_CLASS
        ZFS_AC_KERNEL_CURRENT_BIO_TAIL
+       ZFS_AC_KERNEL_SUPER_USER_NS
        ZFS_AC_KERNEL_SUBMIT_BIO
        ZFS_AC_KERNEL_BDEV_BLOCK_DEVICE_OPERATIONS
        ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID

diff --git a/include/linux/vfs_compat.h b/include/linux/vfs_compat.h
index 97220c2fe6b70b98852f87312585d625c7f13385..fa12ba95a4ac914851ca2ae83d454881469eac43 100644 (file)
--- a/include/linux/vfs_compat.h
+++ b/include/linux/vfs_compat.h
@@ -356,7 +356,11 @@ static inline struct inode *file_inode(const struct file *f)
 #ifdef HAVE_KUID_HELPERS
 static inline uid_t zfs_uid_read_impl(struct inode *ip)
 {
+#ifdef HAVE_SUPER_USER_NS
+       return (from_kuid(ip->i_sb->s_user_ns, ip->i_uid));
+#else
        return (from_kuid(kcred->user_ns, ip->i_uid));
+#endif
 }
 
 static inline uid_t zfs_uid_read(struct inode *ip)
@@ -366,7 +370,11 @@ static inline uid_t zfs_uid_read(struct inode *ip)
 
 static inline gid_t zfs_gid_read_impl(struct inode *ip)
 {
+#ifdef HAVE_SUPER_USER_NS
+       return (from_kgid(ip->i_sb->s_user_ns, ip->i_gid));
+#else
        return (from_kgid(kcred->user_ns, ip->i_gid));
+#endif
 }
 
 static inline gid_t zfs_gid_read(struct inode *ip)
@@ -376,13 +384,22 @@ static inline gid_t zfs_gid_read(struct inode *ip)
 
 static inline void zfs_uid_write(struct inode *ip, uid_t uid)
 {
+#ifdef HAVE_SUPER_USER_NS
+       ip->i_uid = make_kuid(ip->i_sb->s_user_ns, uid);
+#else
        ip->i_uid = make_kuid(kcred->user_ns, uid);
+#endif
 }
 
 static inline void zfs_gid_write(struct inode *ip, gid_t gid)
 {
+#ifdef HAVE_SUPER_USER_NS
+       ip->i_gid = make_kgid(ip->i_sb->s_user_ns, gid);
+#else
        ip->i_gid = make_kgid(kcred->user_ns, gid);
+#endif
 }
+
 #else
 static inline uid_t zfs_uid_read(struct inode *ip)
 {