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Subject[PATCH] kill i_cdev and struct char_device
Struct char_device does nothing but hang in a hash chain,
and consequently is completely superfluous.
The patch below removes it, and the slab cache for them, and
the inode i_cdev field.

[patch against 2.5.59, not clean against current bk;
will resubmit against 2.5.60 when that appears]

[the whole purpose of struct block_device is to provide the link
between a device number and a struct block_device_operations.
struct char_device has no such function, indeed, no function at all]

Andries

diff -u --recursive --new-file -X /linux/dontdiff a/fs/char_dev.c b/fs/char_dev.c
--- a/fs/char_dev.c Fri Nov 22 22:40:28 2002
+++ b/fs/char_dev.c Fri Feb 7 23:23:35 2003
@@ -27,109 +27,6 @@
#define need_serial(ma,mi) (get_tty_driver(mk_kdev(ma,mi)) == NULL)
#endif

-#define HASH_BITS 6
-#define HASH_SIZE (1UL << HASH_BITS)
-#define HASH_MASK (HASH_SIZE-1)
-static struct list_head cdev_hashtable[HASH_SIZE];
-static spinlock_t cdev_lock = SPIN_LOCK_UNLOCKED;
-static kmem_cache_t * cdev_cachep;
-
-#define alloc_cdev() \
- ((struct char_device *) kmem_cache_alloc(cdev_cachep, SLAB_KERNEL))
-#define destroy_cdev(cdev) kmem_cache_free(cdev_cachep, (cdev))
-
-static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
-{
- struct char_device * cdev = (struct char_device *) foo;
-
- if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
- SLAB_CTOR_CONSTRUCTOR)
- {
- memset(cdev, 0, sizeof(*cdev));
- sema_init(&cdev->sem, 1);
- }
-}
-
-void __init cdev_cache_init(void)
-{
- int i;
- struct list_head *head = cdev_hashtable;
-
- i = HASH_SIZE;
- do {
- INIT_LIST_HEAD(head);
- head++;
- i--;
- } while (i);
-
- cdev_cachep = kmem_cache_create("cdev_cache",
- sizeof(struct char_device),
- 0, SLAB_HWCACHE_ALIGN, init_once,
- NULL);
- if (!cdev_cachep)
- panic("Cannot create cdev_cache SLAB cache");
-}
-
-/*
- * Most likely _very_ bad one - but then it's hardly critical for small
- * /dev and can be fixed when somebody will need really large one.
- */
-static inline unsigned long hash(dev_t dev)
-{
- unsigned long tmp = dev;
- tmp = tmp + (tmp >> HASH_BITS) + (tmp >> HASH_BITS*2);
- return tmp & HASH_MASK;
-}
-
-static struct char_device *cdfind(dev_t dev, struct list_head *head)
-{
- struct list_head *p;
- struct char_device *cdev;
- list_for_each(p, head) {
- cdev = list_entry(p, struct char_device, hash);
- if (cdev->dev != dev)
- continue;
- atomic_inc(&cdev->count);
- return cdev;
- }
- return NULL;
-}
-
-struct char_device *cdget(dev_t dev)
-{
- struct list_head * head = cdev_hashtable + hash(dev);
- struct char_device *cdev, *new_cdev;
- spin_lock(&cdev_lock);
- cdev = cdfind(dev, head);
- spin_unlock(&cdev_lock);
- if (cdev)
- return cdev;
- new_cdev = alloc_cdev();
- if (!new_cdev)
- return NULL;
- atomic_set(&new_cdev->count,1);
- new_cdev->dev = dev;
- spin_lock(&cdev_lock);
- cdev = cdfind(dev, head);
- if (!cdev) {
- list_add(&new_cdev->hash, head);
- spin_unlock(&cdev_lock);
- return new_cdev;
- }
- spin_unlock(&cdev_lock);
- destroy_cdev(new_cdev);
- return cdev;
-}
-
-void cdput(struct char_device *cdev)
-{
- if (atomic_dec_and_lock(&cdev->count, &cdev_lock)) {
- list_del(&cdev->hash);
- spin_unlock(&cdev_lock);
- destroy_cdev(cdev);
- }
-}
-
struct device_struct {
const char * name;
struct file_operations * fops;
@@ -155,11 +52,12 @@
}

/*
- Return the function table of a device.
- Load the driver if needed.
- Increment the reference count of module in question.
-*/
-static struct file_operations * get_chrfops(unsigned int major, unsigned int minor)
+ * Return the function table of a device.
+ * Load the driver if needed.
+ * Increment the reference count of module in question.
+ */
+static struct file_operations *
+get_chrfops(unsigned int major, unsigned int minor)
{
struct file_operations *ret = NULL;

@@ -192,7 +90,9 @@
return ret;
}

-int register_chrdev(unsigned int major, const char * name, struct file_operations *fops)
+int
+register_chrdev(unsigned int major, const char *name,
+ struct file_operations *fops)
{
if (devfs_only())
return 0;
diff -u --recursive --new-file -X /linux/dontdiff a/fs/dcache.c b/fs/dcache.c
--- a/fs/dcache.c Fri Nov 22 22:40:20 2002
+++ b/fs/dcache.c Fri Feb 7 23:40:34 2003
@@ -1424,7 +1424,6 @@
EXPORT_SYMBOL(d_genocide);

extern void bdev_cache_init(void);
-extern void cdev_cache_init(void);

void __init vfs_caches_init(unsigned long mempages)
{
@@ -1445,5 +1444,4 @@
files_init(mempages);
mnt_init(mempages);
bdev_cache_init();
- cdev_cache_init();
}
diff -u --recursive --new-file -X /linux/dontdiff a/fs/devfs/base.c b/fs/devfs/base.c
--- a/fs/devfs/base.c Sat Jan 18 23:54:40 2003
+++ b/fs/devfs/base.c Fri Feb 7 23:16:00 2003
@@ -2184,7 +2184,6 @@
if ( S_ISCHR (de->mode) )
{
inode->i_rdev = to_kdev_t(de->u.cdev.dev);
- inode->i_cdev = cdget(de->u.cdev.dev);
}
else if ( S_ISBLK (de->mode) )
{
diff -u --recursive --new-file -X /linux/dontdiff a/fs/inode.c b/fs/inode.c
--- a/fs/inode.c Sat Jan 18 23:54:29 2003
+++ b/fs/inode.c Fri Feb 7 23:17:42 2003
@@ -117,7 +117,6 @@
memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
inode->i_pipe = NULL;
inode->i_bdev = NULL;
- inode->i_cdev = NULL;
inode->i_security = NULL;
if (security_inode_alloc(inode)) {
if (inode->i_sb->s_op->destroy_inode)
@@ -229,10 +228,6 @@
inode->i_sb->s_op->clear_inode(inode);
if (inode->i_bdev)
bd_forget(inode);
- else if (inode->i_cdev) {
- cdput(inode->i_cdev);
- inode->i_cdev = NULL;
- }
inode->i_state = I_CLEAR;
}

@@ -1272,7 +1267,6 @@
if (S_ISCHR(mode)) {
inode->i_fop = &def_chr_fops;
inode->i_rdev = to_kdev_t(rdev);
- inode->i_cdev = cdget(rdev);
} else if (S_ISBLK(mode)) {
inode->i_fop = &def_blk_fops;
inode->i_rdev = to_kdev_t(rdev);
@@ -1281,5 +1275,6 @@
else if (S_ISSOCK(mode))
inode->i_fop = &bad_sock_fops;
else
- printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o)\n", mode);
+ printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o)\n",
+ mode);
}
diff -u --recursive --new-file -X /linux/dontdiff a/include/linux/fs.h b/include/linux/fs.h
--- a/include/linux/fs.h Sat Jan 18 23:54:40 2003
+++ b/include/linux/fs.h Fri Feb 7 23:19:28 2003
@@ -328,14 +328,6 @@
struct address_space *assoc_mapping; /* ditto */
};

-struct char_device {
- struct list_head hash;
- atomic_t count;
- dev_t dev;
- atomic_t openers;
- struct semaphore sem;
-};
-
struct block_device {
struct list_head bd_hash;
atomic_t bd_count;
@@ -382,11 +374,11 @@
struct address_space *i_mapping;
struct address_space i_data;
struct dquot *i_dquot[MAXQUOTAS];
+
/* These three should probably be a union */
struct list_head i_devices;
struct pipe_inode_info *i_pipe;
struct block_device *i_bdev;
- struct char_device *i_cdev;

unsigned long i_dnotify_mask; /* Directory notify events */
struct dnotify_struct *i_dnotify; /* for directory notifications */
@@ -1070,8 +1062,6 @@
extern int bd_acquire(struct inode *inode);
extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
-extern struct char_device *cdget(dev_t);
-extern void cdput(struct char_device *);
extern int blkdev_open(struct inode *, struct file *);
extern int blkdev_close(struct inode *, struct file *);
extern struct file_operations def_blk_fops;
diff -u --recursive --new-file -X /linux/dontdiff a/kernel/ksyms.c b/kernel/ksyms.c
--- a/kernel/ksyms.c Sat Jan 18 23:54:35 2003
+++ b/kernel/ksyms.c Fri Feb 7 23:28:40 2003
@@ -203,8 +203,6 @@
EXPORT_SYMBOL(set_blocksize);
EXPORT_SYMBOL(sb_set_blocksize);
EXPORT_SYMBOL(sb_min_blocksize);
-EXPORT_SYMBOL(cdget);
-EXPORT_SYMBOL(cdput);
EXPORT_SYMBOL(bdget);
EXPORT_SYMBOL(bdput);
EXPORT_SYMBOL(bd_claim);
-
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