FROMGIT: f2fs: set highest IO priority for checkpoint thread

The checkpoint is the top priority thread which can stop all the filesystem
operations. Let's make it RT priority.

Bug: 402201704
Bug: 390504516
Reviewed-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Link: https://lore.kernel.org/linux-f2fs-devel/20250303221730.1284822-1-jaegeuk@kernel.org/T/#u

(cherry picked from commit 8a2d9f00d502e6ef68c6d52f0863856040ddd2db
https: //git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/ dev)
Change-Id: Ife3b87ecff0ad4b8db805c1b15227f3afcd4fbd1
(cherry picked from commit 50eddb3fc9ed6c9f4c3f81df09c4a614d4dd7024)

fs/f2fs/checkpoint.c

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index f767784..ad1a319 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -21,7 +21,7 @@
 #include "iostat.h"
 #include <trace/events/f2fs.h>
 
-#define DEFAULT_CHECKPOINT_IOPRIO (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 3))
+#define DEFAULT_CHECKPOINT_IOPRIO (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 3))
 
 static struct kmem_cache *ino_entry_slab;
 struct kmem_cache *f2fs_inode_entry_slab;