Linux 5.3 (commit 22d94f493bfb) introduces s_master_keys to struct super_block.
As we need encryption support for older kernels, replace this with
new lsi_master_keys field in struct lustre_sb_info.

--- a/libcfs/libcfs/crypto/keyring.c
+++ b/libcfs/libcfs/crypto/keyring.c
@@ -82,7 +82,7 @@ static void llcrypt_key_describe(const s
 }
 
 /*
- * Type of key in ->s_master_keys.  Each key of this type represents a master
+ * Type of key in ->lsi_master_keys.  Each key of this type represents a master
  * key which has been added to the filesystem.  Its payload is a
  * 'struct llcrypt_master_key'.  The "." prefix in the key type name prevents
  * users from adding keys of this type via the keyrings syscalls rather than via
@@ -127,7 +127,7 @@ static struct key_type key_type_llcrypt_
 	.describe		= llcrypt_user_key_describe,
 };
 
-/* Search ->s_master_keys or ->mk_users */
+/* Search ->lsi_master_keys or ->mk_users */
 static struct key *search_llcrypt_keyring(struct key *keyring,
 					  struct key_type *type,
 					  const char *description)
@@ -196,13 +196,17 @@ static void format_mk_user_description(
 		mk_identifier, __kuid_val(current_fsuid()));
 }
 
-/* Create ->s_master_keys if needed.  Synchronized by llcrypt_add_key_mutex. */
+/* Create ->lsi_master_keys if needed.  Synchronized by llcrypt_add_key_mutex. */
 static int allocate_filesystem_keyring(struct super_block *sb)
 {
 	char description[LLCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
 	struct key *keyring;
+	struct lustre_sb_info *lsi = s2lsi(sb);
 
-	if (sb->s_master_keys)
+	if (!lsi)
+		return -EINVAL;
+
+	if (lsi->lsi_master_keys)
 		return 0;
 
 	format_fs_keyring_description(description, sb);
@@ -214,18 +218,22 @@ static int allocate_filesystem_keyring(s
 		return PTR_ERR(keyring);
 
 	/* Pairs with READ_ONCE() in llcrypt_find_master_key() */
-	smp_store_release(&sb->s_master_keys, keyring);
+	smp_store_release(&lsi->lsi_master_keys, keyring);
 	return 0;
 }
 
 void llcrypt_sb_free(struct super_block *sb)
 {
-	key_put(sb->s_master_keys);
-	sb->s_master_keys = NULL;
+	struct lustre_sb_info *lsi = s2lsi(sb);
+
+	if (lsi != NULL) {
+		key_put(lsi->lsi_master_keys);
+		lsi->lsi_master_keys = NULL;
+	}
 }
 
 /*
- * Find the specified master key in ->s_master_keys.
+ * Find the specified master key in ->lsi_master_keys.
  * Returns ERR_PTR(-ENOKEY) if not found.
  */
 struct key *llcrypt_find_master_key(struct super_block *sb,
@@ -233,9 +241,13 @@ struct key *llcrypt_find_master_key(stru
 {
 	struct key *keyring;
 	char description[LLCRYPT_MK_DESCRIPTION_SIZE];
+	struct lustre_sb_info *lsi = s2lsi(sb);
+
+	if (!lsi)
+		return ERR_PTR(-EINVAL);
 
 	/* pairs with smp_store_release() in allocate_filesystem_keyring() */
-	keyring = READ_ONCE(sb->s_master_keys);
+	keyring = READ_ONCE(lsi->lsi_master_keys);
 	if (keyring == NULL)
 		return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
 
@@ -432,8 +444,12 @@ static int add_master_key(struct super_b
 {
 	static DEFINE_MUTEX(llcrypt_add_key_mutex);
 	struct key *key;
+	struct lustre_sb_info *lsi = s2lsi(sb);
 	int err;
 
+	if (!lsi)
+		return -EINVAL;
+
 	mutex_lock(&llcrypt_add_key_mutex); /* serialize find + link */
 retry:
 	key = llcrypt_find_master_key(sb, mk_spec);
@@ -441,14 +457,15 @@ retry:
 		err = PTR_ERR(key);
 		if (err != -ENOKEY)
 			goto out_unlock;
-		/* Didn't find the key in ->s_master_keys.  Add it. */
+		/* Didn't find the key in ->lsi_master_keys.  Add it. */
 		err = allocate_filesystem_keyring(sb);
 		if (err)
 			goto out_unlock;
-		err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
+		err = add_new_master_key(secret, mk_spec,
+					 lsi->lsi_master_keys);
 	} else {
 		/*
-		 * Found the key in ->s_master_keys.  Re-add the secret if
+		 * Found the key in ->lsi_master_keys.  Re-add the secret if
 		 * needed, and add the user to ->mk_users if needed.
 		 */
 		down_write(&key->sem);
--- a/libcfs/libcfs/crypto/keysetup.c
+++ b/libcfs/libcfs/crypto/keysetup.c
@@ -326,7 +326,7 @@ static int setup_file_encryption_key(str
 		/*
 		 * As a legacy fallback for v1 policies, search for the key in
 		 * the current task's subscribed keyrings too.  Don't move this
-		 * to before the search of ->s_master_keys, since users
+		 * to before the search of ->lsi_master_keys, since users
 		 * shouldn't be able to override filesystem-level keys.
 		 */
 		return llcrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
@@ -406,7 +406,7 @@ static void put_crypt_info(struct llcryp
 		 *
 		 * In addition, if we're removing the last inode from a key that
 		 * already had its secret removed, invalidate the key so that it
-		 * gets removed from ->s_master_keys.
+		 * gets removed from ->lsi_master_keys.
 		 */
 		spin_lock(&mk->mk_decrypted_inodes_lock);
 		list_del(&ci->ci_master_key_link);
--- a/libcfs/libcfs/crypto/llcrypt_private.h
+++ b/libcfs/libcfs/crypto/llcrypt_private.h
@@ -13,6 +13,7 @@
 
 #include <libcfs/crypto/llcrypt.h>
 #include <crypto/hash.h>
+#include <lustre_disk.h>
 
 #define CONST_STRLEN(str)	(sizeof(str) - 1)
 
@@ -372,7 +373,7 @@ struct llcrypt_master_key {
 
 	/*
 	 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
-	 * Once this goes to 0, the master key is removed from ->s_master_keys.
+	 * Once this goes to 0, the master key is removed from ->lsi_master_keys.
 	 * The 'struct llcrypt_master_key' will continue to live as long as the
 	 * 'struct key' whose payload it is, but we won't let this reference
 	 * count rise again.