Introduce SIMPLEFS_AT_LEAST to detect versions

As the Linux kernel development continuously changes its kernel APIs,
it is necessary to detect the kernel versions and decide on the
corresponding conditional build paths during the build process. The
SIMPLEFS_AT_LEAST macro is introduced for this purpose.

Author: jserv

inode.c

@@ -223,9 +223,9 @@ static struct inode *simplefs_new_inode(struct inode *dir, mode_t mode)
     }
 
     if (S_ISLNK(mode)) {
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
         inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
         inode_init_owner(&init_user_ns, inode, dir, mode);
 #else
         inode_init_owner(inode, dir, mode);
@@ -255,9 +255,9 @@ static struct inode *simplefs_new_inode(struct inode *dir, mode_t mode)
     }
 
     /* Initialize inode */
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
     inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
     inode_init_owner(&init_user_ns, inode, dir, mode);
 #else
     inode_init_owner(inode, dir, mode);
@@ -302,13 +302,13 @@ static struct inode *simplefs_new_inode(struct inode *dir, mode_t mode)
  *   - cleanup index block of the new inode
  *   - add new file/directory in parent index
  */
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
 static int simplefs_create(struct mnt_idmap *id,
                            struct inode *dir,
                            struct dentry *dentry,
                            umode_t mode,
                            bool excl)
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
 static int simplefs_create(struct user_namespace *ns,
                            struct inode *dir,
                            struct dentry *dentry,
@@ -652,14 +652,14 @@ static int simplefs_unlink(struct inode *dir, struct dentry *dentry)
     return ret;
 }
 
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
 static int simplefs_rename(struct mnt_idmap *id,
                            struct inode *old_dir,
                            struct dentry *old_dentry,
                            struct inode *new_dir,
                            struct dentry *new_dentry,
                            unsigned int flags)
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
 static int simplefs_rename(struct user_namespace *ns,
                            struct inode *old_dir,
                            struct dentry *old_dentry,
@@ -829,15 +829,15 @@ static int simplefs_rename(struct inode *old_dir,
     return ret;
 }
 
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
 static int simplefs_mkdir(struct mnt_idmap *id,
                           struct inode *dir,
                           struct dentry *dentry,
                           umode_t mode)
 {
     return simplefs_create(id, dir, dentry, mode | S_IFDIR, 0);
 }
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
 static int simplefs_mkdir(struct user_namespace *ns,
                           struct inode *dir,
                           struct dentry *dentry,
@@ -954,12 +954,12 @@ static int simplefs_link(struct dentry *old_dentry,
     return ret;
 }
 
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
 static int simplefs_symlink(struct mnt_idmap *id,
                             struct inode *dir,
                             struct dentry *dentry,
                             const char *symname)
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
 static int simplefs_symlink(struct user_namespace *ns,
                             struct inode *dir,
                             struct dentry *dentry,

simplefs.h

@@ -23,11 +23,6 @@
 
 #define SIMPLEFS_MAX_SUBFILES (SIMPLEFS_FILES_PER_EXT * SIMPLEFS_MAX_EXTENTS)
 
-#include <linux/version.h>
-
-#define USER_NS_REQUIRED() LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0)
-#define MNT_IDMAP_REQUIRED() LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0)
-
 /* simplefs partition layout
  * +---------------+
  * |  superblock   |  1 block
@@ -80,6 +75,11 @@ struct simplefs_sb_info {
 };
 
 #ifdef __KERNEL__
+#include <linux/version.h>
+/* compatibility macros */
+#define SIMPLEFS_AT_LEAST(major, minor, rev) \
+    LINUX_VERSION_CODE >= KERNEL_VERSION(major, minor, rev)
+
 struct simplefs_inode_info {
     uint32_t ei_block; /* Block with list of extents for this file */
     char i_data[32];

super.c

@@ -301,9 +301,9 @@ int simplefs_fill_super(struct super_block *sb, void *data, int silent)
         goto free_bfree;
     }
 
-#if MNT_IDMAP_REQUIRED()
+#if SIMPLEFS_AT_LEAST(6, 3, 0)
     inode_init_owner(&nop_mnt_idmap, root_inode, NULL, root_inode->i_mode);
-#elif USER_NS_REQUIRED()
+#elif SIMPLEFS_AT_LEAST(5, 12, 0)
     inode_init_owner(&init_user_ns, root_inode, NULL, root_inode->i_mode);
 #else
     inode_init_owner(root_inode, NULL, root_inode->i_mode);