Support blk_mode_t type and sb_open_mode() helper introduction

Kernel 6.5 replaced the fmode_t type with the blk_mode_t type in the
fs mount procedures, and introduced sb_open_helper() to simplify
calculating its value from mount flags.

These changes were backported to RHEL 9 (RHEL_RELEASE >= 370), so
support them switching their definitions depending on kernel versions.

Signed-off-by: Ryusuke Konishi <[email protected]>

fs/nilfs2/kern_feature.h

@@ -47,6 +47,7 @@
 #  if (RHEL_RELEASE_N >= 370)
 #   define	HAVE_NEW_BLKDEV_GET_AND_PUT	1
 #   define	HAVE_SB_S_MODE			0
+#   define	HAVE_BLK_MODE_T			1
 #  endif
 # else /* !defined(RHEL_RELEASE_N) */
 #  define	HAVE_BD_BDI			0
@@ -72,6 +73,7 @@
 #  if (RHEL_MINOR > 3)				/* RHEL_RELEASE_N >= 363 */
 #   define	HAVE_NEW_BLKDEV_GET_AND_PUT	1
 #   define	HAVE_SB_S_MODE			0
+#   define	HAVE_BLK_MODE_T			1
 #  endif
 # endif
 #endif
@@ -210,6 +212,15 @@
 # define HAVE_SB_S_MODE \
 	(LINUX_VERSION_CODE < KERNEL_VERSION(6, 5, 0))
 #endif
+/*
+ * In kernel 6.5, regarding block open flags, fmode_t has been replaced
+ * with block-specific type (BLK_OPEN_*) and sb_open_mode() helper has
+ * been added to simplify calculating its value from mount flags.
+ */
+#ifndef HAVE_BLK_MODE_T
+# define HAVE_BLK_MODE_T \
+	(LINUX_VERSION_CODE >= KERNEL_VERSION(6, 5, 0))
+#endif
 #endif /* LINUX_VERSION_CODE */
 
 
@@ -291,4 +302,10 @@ compat_submit_bh(int mode, int mode_flags, struct buffer_head *bh)
 	blkdev_put(bdev, mode)
 #endif
 
+#if !HAVE_BLK_MODE_T
+typedef fmode_t blk_mode_t;
+#define sb_open_mode(flags) \
+	(FMODE_READ | FMODE_EXCL | (((flags) & SB_RDONLY) ? 0 : FMODE_WRITE))
+#endif
+
 #endif /* NILFS_KERN_FEATURE_H */

fs/nilfs2/super.c

@@ -1306,13 +1306,10 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 {
 	struct nilfs_super_data sd;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ | FMODE_EXCL;
+	blk_mode_t mode = sb_open_mode(flags);
 	struct dentry *root_dentry;
 	int err, s_new = false;
 
-	if (!(flags & SB_RDONLY))
-		mode |= FMODE_WRITE;
-
 	sd.bdev = compat_blkdev_get_by_path(dev_name, mode, fs_type, NULL);
 	if (IS_ERR(sd.bdev))
 		return ERR_CAST(sd.bdev);