diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index 6b71852dadc277c638310beb63d89064024e7d5b..4ec843123cc3bd1f206aa8b2315b3acad11b1a88 100644
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -3081,3 +3081,8 @@
1 = /dev/osd1 Second OSD Device
...
255 = /dev/osd255 256th OSD Device
+
+ 384-511 char RESERVED FOR DYNAMIC ASSIGNMENT
+ Character devices that request a dynamic allocation of major
+ number will take numbers starting from 511 and downward,
+ once the 234-254 range is full.
diff --git a/fs/char_dev.c b/fs/char_dev.c
index fb8507f521b265ba8feba385154cc908eb812f44..c9d18362e89de0a060f96ae8e41cc05543c9dc6f 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -59,6 +59,29 @@ void chrdev_show(struct seq_file *f, off_t offset)
#endif /* CONFIG_PROC_FS */
+static int find_dynamic_major(void)
+{
+ int i;
+ struct char_device_struct *cd;
+
+ for (i = ARRAY_SIZE(chrdevs)-1; i > CHRDEV_MAJOR_DYN_END; i--) {
+ if (chrdevs[i] == NULL)
+ return i;
+ }
+
+ for (i = CHRDEV_MAJOR_DYN_EXT_START;
+ i > CHRDEV_MAJOR_DYN_EXT_END; i--) {
+ for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)
+ if (cd->major == i)
+ break;
+
+ if (cd == NULL || cd->major != i)
+ return i;
+ }
+
+ return -EBUSY;
+}
+
/*
* Register a single major with a specified minor range.
*
@@ -84,22 +107,14 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
mutex_lock(&chrdevs_lock);
- /* temporary */
if (major == 0) {
- for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
- if (chrdevs[i] == NULL)
- break;
- }
-
- if (i < CHRDEV_MAJOR_DYN_END)
- pr_warn("CHRDEV \"%s\" major number %d goes below the dynamic allocation range\n",
- name, i);
-
- if (i == 0) {
- ret = -EBUSY;
+ ret = find_dynamic_major();
+ if (ret < 0) {
+ pr_err("CHRDEV \"%s\" dynamic allocation region is full\n",
+ name);
goto out;
}
- major = i;
+ major = ret;
}
cd->major = major;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7b5d6816542b7f5af171d5680961aeb03184707b..1773dcf1e3180b19a1c14d81e287ef07739efaff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2473,6 +2473,10 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
#define CHRDEV_MAJOR_HASH_SIZE 255
/* Marks the bottom of the first segment of free char majors */
#define CHRDEV_MAJOR_DYN_END 234
+/* Marks the top and bottom of the second segment of free char majors */
+#define CHRDEV_MAJOR_DYN_EXT_START 511
+#define CHRDEV_MAJOR_DYN_EXT_END 384
+
extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
extern int register_chrdev_region(dev_t, unsigned, const char *);
extern int __register_chrdev(unsigned int major, unsigned int baseminor,