[PATCH] *: mark stuff as __ro_after_init

From: Alexey Dobriyan
Date: Wed Oct 11 2023 - 12:55:11 EST

__read_mostly predates __ro_after_init. Many variables which are marked
__read_mostly should have been __ro_after_init from day 1.

Also, mark some stuff as "const" and "__init" while I'm at it.

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

block/bdev.c | 6 +++---
fs/anon_inodes.c | 4 ++--
fs/buffer.c | 4 ++--
fs/char_dev.c | 2 +-
fs/dcache.c | 8 ++++----
fs/direct-io.c | 2 +-
fs/eventpoll.c | 6 +++---
fs/fcntl.c | 2 +-
fs/file.c | 4 ++--
fs/file_table.c | 2 +-
fs/inode.c | 8 ++++----
fs/kernfs/mount.c | 5 +++--
fs/locks.c | 4 ++--
fs/namespace.c | 16 ++++++++--------
fs/notify/dnotify/dnotify.c | 6 +++---
fs/notify/fanotify/fanotify_user.c | 8 ++++----
fs/notify/inotify/inotify_user.c | 2 +-
fs/pipe.c | 2 +-
fs/userfaultfd.c | 2 +-
include/linux/file.h | 3 ++-
kernel/audit_tree.c | 4 ++--
kernel/sched/core.c | 2 +-
kernel/user_namespace.c | 2 +-
kernel/workqueue.c | 16 ++++++++--------
lib/debugobjects.c | 2 +-
mm/khugepaged.c | 2 +-
mm/shmem.c | 8 ++++----
security/integrity/iint.c | 2 +-
28 files changed, 68 insertions(+), 66 deletions(-)

--- a/block/bdev.c
+++ b/block/bdev.c
@@ -292,7 +292,7 @@ EXPORT_SYMBOL(thaw_bdev);
*/

static __cacheline_aligned_in_smp DEFINE_MUTEX(bdev_lock);
-static struct kmem_cache * bdev_cachep __read_mostly;
+static struct kmem_cache * bdev_cachep __ro_after_init;

static struct inode *bdev_alloc_inode(struct super_block *sb)
{
@@ -361,13 +361,13 @@ static struct file_system_type bd_type = {
.kill_sb = kill_anon_super,
};

-struct super_block *blockdev_superblock __read_mostly;
+struct super_block *blockdev_superblock __ro_after_init;
EXPORT_SYMBOL_GPL(blockdev_superblock);

void __init bdev_cache_init(void)
{
int err;
- static struct vfsmount *bd_mnt;
+ static struct vfsmount *bd_mnt __ro_after_init;

bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -24,8 +24,8 @@

#include <linux/uaccess.h>

-static struct vfsmount *anon_inode_mnt __read_mostly;
-static struct inode *anon_inode_inode;
+static struct vfsmount *anon_inode_mnt __ro_after_init;
+static struct inode *anon_inode_inode __ro_after_init;

/*
* anon_inodefs_dname() is called from d_path().
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2988,13 +2988,13 @@ EXPORT_SYMBOL(try_to_free_buffers);
/*
* Buffer-head allocation
*/
-static struct kmem_cache *bh_cachep __read_mostly;
+static struct kmem_cache *bh_cachep __ro_after_init;

/*
* Once the number of bh's in the machine exceeds this level, we start
* stripping them in writeback.
*/
-static unsigned long max_buffer_heads;
+static unsigned long max_buffer_heads __ro_after_init;

int buffer_heads_over_limit;

--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -25,7 +25,7 @@

#include "internal.h"

-static struct kobj_map *cdev_map;
+static struct kobj_map *cdev_map __ro_after_init;

static DEFINE_MUTEX(chrdevs_lock);

--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -78,7 +78,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);

EXPORT_SYMBOL(rename_lock);

-static struct kmem_cache *dentry_cache __read_mostly;
+static struct kmem_cache *dentry_cache __ro_after_init;

const struct qstr empty_name = QSTR_INIT("", 0);
EXPORT_SYMBOL(empty_name);
@@ -96,9 +96,9 @@ EXPORT_SYMBOL(dotdot_name);
* information, yet avoid using a prime hash-size or similar.
*/

-static unsigned int d_hash_shift __read_mostly;
+static unsigned int d_hash_shift __ro_after_init;

-static struct hlist_bl_head *dentry_hashtable __read_mostly;
+static struct hlist_bl_head *dentry_hashtable __ro_after_init;

static inline struct hlist_bl_head *d_hash(unsigned int hash)
{
@@ -3324,7 +3324,7 @@ static void __init dcache_init(void)
}

/* SLAB cache for __getname() consumers */
-struct kmem_cache *names_cachep __read_mostly;
+struct kmem_cache *names_cachep __ro_after_init;
EXPORT_SYMBOL(names_cachep);

void __init vfs_caches_init_early(void)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -151,7 +151,7 @@ struct dio {
};
} ____cacheline_aligned_in_smp;

-static struct kmem_cache *dio_cache __read_mostly;
+static struct kmem_cache *dio_cache __ro_after_init;

/*
* How many pages are in the queue?
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -256,10 +256,10 @@ static u64 loop_check_gen = 0;
static struct eventpoll *inserting_into;

/* Slab cache used to allocate "struct epitem" */
-static struct kmem_cache *epi_cache __read_mostly;
+static struct kmem_cache *epi_cache __ro_after_init;

/* Slab cache used to allocate "struct eppoll_entry" */
-static struct kmem_cache *pwq_cache __read_mostly;
+static struct kmem_cache *pwq_cache __ro_after_init;

/*
* List of files with newly added links, where we may need to limit the number
@@ -271,7 +271,7 @@ struct epitems_head {
};
static struct epitems_head *tfile_check_list = EP_UNACTIVE_PTR;

-static struct kmem_cache *ephead_cache __read_mostly;
+static struct kmem_cache *ephead_cache __ro_after_init;

static inline void free_ephead(struct epitems_head *head)
{
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -844,7 +844,7 @@ int send_sigurg(struct fown_struct *fown)
}

static DEFINE_SPINLOCK(fasync_lock);
-static struct kmem_cache *fasync_cache __read_mostly;
+static struct kmem_cache *fasync_cache __ro_after_init;

static void fasync_free_rcu(struct rcu_head *head)
{
--- a/fs/file.c
+++ b/fs/file.c
@@ -25,10 +25,10 @@
#include "internal.h"

unsigned int sysctl_nr_open __read_mostly = 1024*1024;
-unsigned int sysctl_nr_open_min = BITS_PER_LONG;
+const unsigned int sysctl_nr_open_min = BITS_PER_LONG;
/* our min() is unusable in constant expressions ;-/ */
#define __const_min(x, y) ((x) < (y) ? (x) : (y))
-unsigned int sysctl_nr_open_max =
+const unsigned int sysctl_nr_open_max =
__const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;

static void __free_fdtable(struct fdtable *fdt)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -40,7 +40,7 @@ static struct files_stat_struct files_stat = {
};

/* SLAB cache for file structures */
-static struct kmem_cache *filp_cachep __read_mostly;
+static struct kmem_cache *filp_cachep __ro_after_init;

static struct percpu_counter nr_files __cacheline_aligned_in_smp;

--- a/fs/inode.c
+++ b/fs/inode.c
@@ -54,9 +54,9 @@
* inode_hash_lock
*/

-static unsigned int i_hash_mask __read_mostly;
-static unsigned int i_hash_shift __read_mostly;
-static struct hlist_head *inode_hashtable __read_mostly;
+static unsigned int i_hash_mask __ro_after_init;
+static unsigned int i_hash_shift __ro_after_init;
+static struct hlist_head *inode_hashtable __ro_after_init;
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);

/*
@@ -70,7 +70,7 @@ EXPORT_SYMBOL(empty_aops);
static DEFINE_PER_CPU(unsigned long, nr_inodes);
static DEFINE_PER_CPU(unsigned long, nr_unused);

-static struct kmem_cache *inode_cachep __read_mostly;
+static struct kmem_cache *inode_cachep __ro_after_init;

static long get_nr_inodes(void)
{
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -21,8 +21,9 @@

#include "kernfs-internal.h"

-struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
-struct kernfs_global_locks *kernfs_locks;
+struct kmem_cache *kernfs_node_cache __ro_after_init;
+struct kmem_cache *kernfs_iattrs_cache __ro_after_init;
+struct kernfs_global_locks *kernfs_locks __ro_after_init;

static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
{
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -167,8 +167,8 @@ static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
*/
static DEFINE_SPINLOCK(blocked_lock_lock);

-static struct kmem_cache *flctx_cache __read_mostly;
-static struct kmem_cache *filelock_cache __read_mostly;
+static struct kmem_cache *flctx_cache __ro_after_init;
+static struct kmem_cache *filelock_cache __ro_after_init;

static struct file_lock_context *
locks_get_lock_context(struct inode *inode, int type)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -39,10 +39,10 @@
/* Maximum number of mounts in a mount namespace */
static unsigned int sysctl_mount_max __read_mostly = 100000;

-static unsigned int m_hash_mask __read_mostly;
-static unsigned int m_hash_shift __read_mostly;
-static unsigned int mp_hash_mask __read_mostly;
-static unsigned int mp_hash_shift __read_mostly;
+static unsigned int m_hash_mask __ro_after_init;
+static unsigned int m_hash_shift __ro_after_init;
+static unsigned int mp_hash_mask __ro_after_init;
+static unsigned int mp_hash_shift __ro_after_init;

static __initdata unsigned long mhash_entries;
static int __init set_mhash_entries(char *str)
@@ -68,9 +68,9 @@ static u64 event;
static DEFINE_IDA(mnt_id_ida);
static DEFINE_IDA(mnt_group_ida);

-static struct hlist_head *mount_hashtable __read_mostly;
-static struct hlist_head *mountpoint_hashtable __read_mostly;
-static struct kmem_cache *mnt_cache __read_mostly;
+static struct hlist_head *mount_hashtable __ro_after_init;
+static struct hlist_head *mountpoint_hashtable __ro_after_init;
+static struct kmem_cache *mnt_cache __ro_after_init;
static DECLARE_RWSEM(namespace_sem);
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
@@ -86,7 +86,7 @@ struct mount_kattr {
};

/* /sys/fs */
-struct kobject *fs_kobj;
+struct kobject *fs_kobj __ro_after_init;
EXPORT_SYMBOL_GPL(fs_kobj);

/*
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -39,9 +39,9 @@ static void __init dnotify_sysctl_init(void)
#define dnotify_sysctl_init() do { } while (0)
#endif

-static struct kmem_cache *dnotify_struct_cache __read_mostly;
-static struct kmem_cache *dnotify_mark_cache __read_mostly;
-static struct fsnotify_group *dnotify_group __read_mostly;
+static struct kmem_cache *dnotify_struct_cache __ro_after_init;
+static struct kmem_cache *dnotify_mark_cache __ro_after_init;
+static struct fsnotify_group *dnotify_group __ro_after_init;

/*
* dnotify will attach one of these to each inode (i_fsnotify_marks) which
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -112,10 +112,10 @@ static void __init fanotify_sysctls_init(void)

extern const struct fsnotify_ops fanotify_fsnotify_ops;

-struct kmem_cache *fanotify_mark_cache __read_mostly;
-struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
-struct kmem_cache *fanotify_path_event_cachep __read_mostly;
-struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
+struct kmem_cache *fanotify_mark_cache __ro_after_init;
+struct kmem_cache *fanotify_fid_event_cachep __ro_after_init;
+struct kmem_cache *fanotify_path_event_cachep __ro_after_init;
+struct kmem_cache *fanotify_perm_event_cachep __ro_after_init;

#define FANOTIFY_EVENT_ALIGN 4
#define FANOTIFY_FID_INFO_HDR_LEN \
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -49,7 +49,7 @@
/* configurable via /proc/sys/fs/inotify/ */
static int inotify_max_queued_events __read_mostly;

-struct kmem_cache *inotify_inode_mark_cachep __read_mostly;
+struct kmem_cache *inotify_inode_mark_cachep __ro_after_init;

#ifdef CONFIG_SYSCTL

--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -854,7 +854,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
kfree(pipe);
}

-static struct vfsmount *pipe_mnt __read_mostly;
+static struct vfsmount *pipe_mnt __ro_after_init;

/*
* pipefs_dname() is called from d_path().
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -49,7 +49,7 @@ static struct ctl_table vm_userfaultfd_table[] = {
};
#endif

-static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
+static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init;

/*
* Start with fault_pending_wqh and fault_wqh so they're more likely
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -113,6 +113,7 @@ int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags);
extern void flush_delayed_fput(void);
extern void __fput_sync(struct file *);

-extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
+extern const unsigned int sysctl_nr_open_min;
+extern const unsigned int sysctl_nr_open_max;

#endif /* __LINUX_FILE_H */
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -87,8 +87,8 @@ static struct task_struct *prune_thread;
* that makes a difference. Some.
*/

-static struct fsnotify_group *audit_tree_group;
-static struct kmem_cache *audit_tree_mark_cachep __read_mostly;
+static struct fsnotify_group *audit_tree_group __ro_after_init;
+static struct kmem_cache *audit_tree_mark_cachep __ro_after_init;

static struct audit_tree *alloc_tree(const char *s)
{
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9903,7 +9903,7 @@ struct task_group root_task_group;
LIST_HEAD(task_groups);

/* Cacheline aligned slab cache for task_group */
-static struct kmem_cache *task_group_cache __read_mostly;
+static struct kmem_cache *task_group_cache __ro_after_init;
#endif

void __init sched_init(void)
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -22,7 +22,7 @@
#include <linux/bsearch.h>
#include <linux/sort.h>

-static struct kmem_cache *user_ns_cachep __read_mostly;
+static struct kmem_cache *user_ns_cachep __ro_after_init;
static DEFINE_MUTEX(userns_state_mutex);

static bool new_idmap_permitted(const struct file *file,
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -418,21 +418,21 @@ static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
* process context while holding a pool lock. Bounce to a dedicated kthread
* worker to avoid A-A deadlocks.
*/
-static struct kthread_worker *pwq_release_worker;
+static struct kthread_worker *pwq_release_worker __ro_after_init;

-struct workqueue_struct *system_wq __read_mostly;
+struct workqueue_struct *system_wq __ro_after_init;
EXPORT_SYMBOL(system_wq);
-struct workqueue_struct *system_highpri_wq __read_mostly;
+struct workqueue_struct *system_highpri_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_highpri_wq);
-struct workqueue_struct *system_long_wq __read_mostly;
+struct workqueue_struct *system_long_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_long_wq);
-struct workqueue_struct *system_unbound_wq __read_mostly;
+struct workqueue_struct *system_unbound_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_unbound_wq);
-struct workqueue_struct *system_freezable_wq __read_mostly;
+struct workqueue_struct *system_freezable_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_freezable_wq);
-struct workqueue_struct *system_power_efficient_wq __read_mostly;
+struct workqueue_struct *system_power_efficient_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_power_efficient_wq);
-struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
+struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);

static int worker_thread(void *__worker);
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -89,7 +89,7 @@ static int debug_objects_pool_size __read_mostly
static int debug_objects_pool_min_level __read_mostly
= ODEBUG_POOL_MIN_LEVEL;
static const struct debug_obj_descr *descr_test __read_mostly;
-static struct kmem_cache *obj_cache __read_mostly;
+static struct kmem_cache *obj_cache __ro_after_init;

/*
* Track numbers of kmem_cache_alloc()/free() calls done.
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -91,7 +91,7 @@ static unsigned int khugepaged_max_ptes_shared __read_mostly;
#define MM_SLOTS_HASH_BITS 10
static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);

-static struct kmem_cache *mm_slot_cache __read_mostly;
+static struct kmem_cache *mm_slot_cache __ro_after_init;

struct collapse_control {
bool is_khugepaged;
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -42,7 +42,7 @@
#include <linux/iversion.h>
#include "swap.h"

-static struct vfsmount *shm_mnt;
+static struct vfsmount *shm_mnt __ro_after_init;

#ifdef CONFIG_SHMEM
/*
@@ -4394,7 +4394,7 @@ static const struct fs_context_operations shmem_fs_context_ops = {
#endif
};

-static struct kmem_cache *shmem_inode_cachep;
+static struct kmem_cache *shmem_inode_cachep __ro_after_init;

static struct inode *shmem_alloc_inode(struct super_block *sb)
{
@@ -4426,14 +4426,14 @@ static void shmem_init_inode(void *foo)
inode_init_once(&info->vfs_inode);
}

-static void shmem_init_inodecache(void)
+static void __init shmem_init_inodecache(void)
{
shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
sizeof(struct shmem_inode_info),
0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
}

-static void shmem_destroy_inodecache(void)
+static void __init shmem_destroy_inodecache(void)
{
kmem_cache_destroy(shmem_inode_cachep);
}
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -23,7 +23,7 @@

static struct rb_root integrity_iint_tree = RB_ROOT;
static DEFINE_RWLOCK(integrity_iint_lock);
-static struct kmem_cache *iint_cache __read_mostly;
+static struct kmem_cache *iint_cache __ro_after_init;

struct dentry *integrity_dir;