[PATCH] char_dev: replace cdev_map with an xarray
From: Christoph Hellwig
Date: Mon Jan 11 2021 - 12:06:10 EST
None of the complicated overlapping regions bits of the kobj_map are
required for the character device lookup, so just a trivial xarray
instead.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
drivers/base/Makefile | 5 +-
drivers/base/map.c | 154 ---------------------------------------
fs/char_dev.c | 93 ++++++++++++-----------
fs/dcache.c | 1 -
fs/internal.h | 5 --
include/linux/kobj_map.h | 20 -----
6 files changed, 48 insertions(+), 230 deletions(-)
delete mode 100644 drivers/base/map.c
delete mode 100644 include/linux/kobj_map.h
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 5e7bf9669a81f8..ff0be4d875cfaf 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -1,9 +1,8 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for the Linux device tree
-obj-y := component.o core.o bus.o dd.o syscore.o \
- driver.o class.o platform.o \
- cpu.o firmware.o init.o map.o devres.o \
+obj-y := component.o core.o bus.o dd.o syscore.o driver.o \
+ class.o platform.o cpu.o firmware.o init.o devres.o \
attribute_container.o transport_class.o \
topology.o container.o property.o cacheinfo.o \
swnode.o
diff --git a/drivers/base/map.c b/drivers/base/map.c
deleted file mode 100644
index 5650ab2b247ada..00000000000000
--- a/drivers/base/map.c
+++ /dev/null
@@ -1,154 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * linux/drivers/base/map.c
- *
- * (C) Copyright Al Viro 2002,2003
- *
- * NOTE: data structure needs to be changed. It works, but for large dev_t
- * it will be too slow. It is isolated, though, so these changes will be
- * local to that file.
- */
-
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/mutex.h>
-#include <linux/kdev_t.h>
-#include <linux/kobject.h>
-#include <linux/kobj_map.h>
-
-struct kobj_map {
- struct probe {
- struct probe *next;
- dev_t dev;
- unsigned long range;
- struct module *owner;
- kobj_probe_t *get;
- int (*lock)(dev_t, void *);
- void *data;
- } *probes[255];
- struct mutex *lock;
-};
-
-int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
- struct module *module, kobj_probe_t *probe,
- int (*lock)(dev_t, void *), void *data)
-{
- unsigned n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
- unsigned index = MAJOR(dev);
- unsigned i;
- struct probe *p;
-
- if (n > 255)
- n = 255;
-
- p = kmalloc_array(n, sizeof(struct probe), GFP_KERNEL);
- if (p == NULL)
- return -ENOMEM;
-
- for (i = 0; i < n; i++, p++) {
- p->owner = module;
- p->get = probe;
- p->lock = lock;
- p->dev = dev;
- p->range = range;
- p->data = data;
- }
- mutex_lock(domain->lock);
- for (i = 0, p -= n; i < n; i++, p++, index++) {
- struct probe **s = &domain->probes[index % 255];
- while (*s && (*s)->range < range)
- s = &(*s)->next;
- p->next = *s;
- *s = p;
- }
- mutex_unlock(domain->lock);
- return 0;
-}
-
-void kobj_unmap(struct kobj_map *domain, dev_t dev, unsigned long range)
-{
- unsigned n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
- unsigned index = MAJOR(dev);
- unsigned i;
- struct probe *found = NULL;
-
- if (n > 255)
- n = 255;
-
- mutex_lock(domain->lock);
- for (i = 0; i < n; i++, index++) {
- struct probe **s;
- for (s = &domain->probes[index % 255]; *s; s = &(*s)->next) {
- struct probe *p = *s;
- if (p->dev == dev && p->range == range) {
- *s = p->next;
- if (!found)
- found = p;
- break;
- }
- }
- }
- mutex_unlock(domain->lock);
- kfree(found);
-}
-
-struct kobject *kobj_lookup(struct kobj_map *domain, dev_t dev, int *index)
-{
- struct kobject *kobj;
- struct probe *p;
- unsigned long best = ~0UL;
-
-retry:
- mutex_lock(domain->lock);
- for (p = domain->probes[MAJOR(dev) % 255]; p; p = p->next) {
- struct kobject *(*probe)(dev_t, int *, void *);
- struct module *owner;
- void *data;
-
- if (p->dev > dev || p->dev + p->range - 1 < dev)
- continue;
- if (p->range - 1 >= best)
- break;
- if (!try_module_get(p->owner))
- continue;
- owner = p->owner;
- data = p->data;
- probe = p->get;
- best = p->range - 1;
- *index = dev - p->dev;
- if (p->lock && p->lock(dev, data) < 0) {
- module_put(owner);
- continue;
- }
- mutex_unlock(domain->lock);
- kobj = probe(dev, index, data);
- /* Currently ->owner protects _only_ ->probe() itself. */
- module_put(owner);
- if (kobj)
- return kobj;
- goto retry;
- }
- mutex_unlock(domain->lock);
- return NULL;
-}
-
-struct kobj_map *kobj_map_init(kobj_probe_t *base_probe, struct mutex *lock)
-{
- struct kobj_map *p = kmalloc(sizeof(struct kobj_map), GFP_KERNEL);
- struct probe *base = kzalloc(sizeof(*base), GFP_KERNEL);
- int i;
-
- if ((p == NULL) || (base == NULL)) {
- kfree(p);
- kfree(base);
- return NULL;
- }
-
- base->dev = 1;
- base->range = ~0;
- base->get = base_probe;
- for (i = 0; i < 255; i++)
- p->probes[i] = base;
- p->lock = lock;
- return p;
-}
diff --git a/fs/char_dev.c b/fs/char_dev.c
index ba0ded7842a779..82c26ed407ff65 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -17,7 +17,6 @@
#include <linux/seq_file.h>
#include <linux/kobject.h>
-#include <linux/kobj_map.h>
#include <linux/cdev.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
@@ -25,8 +24,7 @@
#include "internal.h"
-static struct kobj_map *cdev_map;
-
+static DEFINE_XARRAY(cdev_map);
static DEFINE_MUTEX(chrdevs_lock);
#define CHRDEV_MAJOR_HASH_SIZE 255
@@ -367,6 +365,28 @@ void cdev_put(struct cdev *p)
}
}
+static struct cdev *cdev_lookup(dev_t dev)
+{
+ struct cdev *cdev;
+
+ mutex_lock(&chrdevs_lock);
+ cdev = xa_load(&cdev_map, dev);
+ if (!cdev) {
+ mutex_unlock(&chrdevs_lock);
+ if (request_module("char-major-%d-%d",
+ MAJOR(dev), MINOR(dev)) > 0)
+ /* Make old-style 2.4 aliases work */
+ request_module("char-major-%d", MAJOR(dev));
+ mutex_lock(&chrdevs_lock);
+
+ cdev = xa_load(&cdev_map, dev);
+ }
+ if (cdev && !cdev_get(cdev))
+ cdev = NULL;
+ mutex_unlock(&chrdevs_lock);
+ return cdev;
+}
+
/*
* Called every time a character special file is opened
*/
@@ -380,13 +400,10 @@ static int chrdev_open(struct inode *inode, struct file *filp)
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
- struct kobject *kobj;
- int idx;
spin_unlock(&cdev_lock);
- kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
- if (!kobj)
+ new = cdev_lookup(inode->i_rdev);
+ if (!new)
return -ENXIO;
- new = container_of(kobj, struct cdev, kobj);
spin_lock(&cdev_lock);
/* Check i_cdev again in case somebody beat us to it while
we dropped the lock. */
@@ -454,18 +471,6 @@ const struct file_operations def_chr_fops = {
.llseek = noop_llseek,
};
-static struct kobject *exact_match(dev_t dev, int *part, void *data)
-{
- struct cdev *p = data;
- return &p->kobj;
-}
-
-static int exact_lock(dev_t dev, void *data)
-{
- struct cdev *p = data;
- return cdev_get(p) ? 0 : -1;
-}
-
/**
* cdev_add() - add a char device to the system
* @p: the cdev structure for the device
@@ -478,7 +483,7 @@ static int exact_lock(dev_t dev, void *data)
*/
int cdev_add(struct cdev *p, dev_t dev, unsigned count)
{
- int error;
+ int error, i;
p->dev = dev;
p->count = count;
@@ -486,14 +491,22 @@ int cdev_add(struct cdev *p, dev_t dev, unsigned count)
if (WARN_ON(dev == WHITEOUT_DEV))
return -EBUSY;
- error = kobj_map(cdev_map, dev, count, NULL,
- exact_match, exact_lock, p);
- if (error)
- return error;
+ mutex_lock(&chrdevs_lock);
+ for (i = 0; i < count; i++) {
+ error = xa_insert(&cdev_map, dev + i, p, GFP_KERNEL);
+ if (error)
+ goto out_unwind;
+ }
+ mutex_unlock(&chrdevs_lock);
kobject_get(p->kobj.parent);
-
return 0;
+
+out_unwind:
+ while (--i >= 0)
+ xa_erase(&cdev_map, dev + i);
+ mutex_unlock(&chrdevs_lock);
+ return error;
}
/**
@@ -575,11 +588,6 @@ void cdev_device_del(struct cdev *cdev, struct device *dev)
cdev_del(cdev);
}
-static void cdev_unmap(dev_t dev, unsigned count)
-{
- kobj_unmap(cdev_map, dev, count);
-}
-
/**
* cdev_del() - remove a cdev from the system
* @p: the cdev structure to be removed
@@ -593,11 +601,16 @@ static void cdev_unmap(dev_t dev, unsigned count)
*/
void cdev_del(struct cdev *p)
{
- cdev_unmap(p->dev, p->count);
+ int i;
+
+ mutex_lock(&chrdevs_lock);
+ for (i = 0; i < p->count; i++)
+ xa_erase(&cdev_map, p->dev + i);
+ mutex_unlock(&chrdevs_lock);
+
kobject_put(&p->kobj);
}
-
static void cdev_default_release(struct kobject *kobj)
{
struct cdev *p = container_of(kobj, struct cdev, kobj);
@@ -656,20 +669,6 @@ void cdev_init(struct cdev *cdev, const struct file_operations *fops)
cdev->ops = fops;
}
-static struct kobject *base_probe(dev_t dev, int *part, void *data)
-{
- if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
- /* Make old-style 2.4 aliases work */
- request_module("char-major-%d", MAJOR(dev));
- return NULL;
-}
-
-void __init chrdev_init(void)
-{
- cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
-}
-
-
/* Let modules do char dev stuff */
EXPORT_SYMBOL(register_chrdev_region);
EXPORT_SYMBOL(unregister_chrdev_region);
diff --git a/fs/dcache.c b/fs/dcache.c
index 97e81a844a966c..3e0329b3de0a2d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3240,5 +3240,4 @@ void __init vfs_caches_init(void)
files_maxfiles_init();
mnt_init();
bdev_cache_init();
- chrdev_init();
}
diff --git a/fs/internal.h b/fs/internal.h
index 77c50befbfbe96..a2985ee25c3b15 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -50,11 +50,6 @@ static inline int emergency_thaw_bdev(struct super_block *sb)
extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
get_block_t *get_block, struct iomap *iomap);
-/*
- * char_dev.c
- */
-extern void __init chrdev_init(void);
-
/*
* fs_context.c
*/
diff --git a/include/linux/kobj_map.h b/include/linux/kobj_map.h
deleted file mode 100644
index c9919f8b22932c..00000000000000
--- a/include/linux/kobj_map.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * kobj_map.h
- */
-
-#ifndef _KOBJ_MAP_H_
-#define _KOBJ_MAP_H_
-
-#include <linux/mutex.h>
-
-typedef struct kobject *kobj_probe_t(dev_t, int *, void *);
-struct kobj_map;
-
-int kobj_map(struct kobj_map *, dev_t, unsigned long, struct module *,
- kobj_probe_t *, int (*)(dev_t, void *), void *);
-void kobj_unmap(struct kobj_map *, dev_t, unsigned long);
-struct kobject *kobj_lookup(struct kobj_map *, dev_t, int *);
-struct kobj_map *kobj_map_init(kobj_probe_t *, struct mutex *);
-
-#endif /* _KOBJ_MAP_H_ */
--
2.29.2