ext4: preserve SB_I_VERSION on remount

IMA testing revealed that after an ext4 remount, file accesses triggered
full measurements even without modifications, instead of skipping as
expected when i_version is unchanged.

Debugging showed `SB_I_VERSION` was cleared in reconfigure_super() during
remount due to commit 1ff2030 ("ext4: unconditionally enable the
i_version counter") removing the fix from commit 960e0ab ("ext4: fix
i_version handling on remount").

To rectify this, `SB_I_VERSION` is always set for `fc->sb_flags` in
ext4_init_fs_context(), instead of `sb->s_flags` in __ext4_fill_super(),
ensuring it persists across all mounts.

Cc: stable@kernel.org
Fixes: 1ff2030 ("ext4: unconditionally enable the i_version counter")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250703073903.6952-2-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

fs/ext4/super.c

@@ -1998,6 +1998,9 @@ int ext4_init_fs_context(struct fs_context *fc)
 	fc->fs_private = ctx;
 	fc->ops = &ext4_context_ops;
 
+	/* i_version is always enabled now */
+	fc->sb_flags |= SB_I_VERSION;
+
 	return 0;
 }
 
@@ -5316,9 +5319,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
 		(test_opt(sb, POSIX_ACL) ? SB_POSIXACL : 0);
 
-	/* i_version is always enabled now */
-	sb->s_flags |= SB_I_VERSION;
-
 	/* HSM events are allowed by default. */
 	sb->s_iflags |= SB_I_ALLOW_HSM;